Comparative in vitro and in silico analysis of the ability of basic Asp49 phospholipase A2 and Lys49-phospholipase A2-like myotoxins from Bothrops diporus venom to inhibit the metastatic potential of murine mammary tumor cells and endothelial cell tubulogenesis: Asp49 vs Lys49 phospholipases A2: Inhibition of metastasis and angiogenesis.

Snake venoms are a complex mixture of proteins and polypeptides that represent a valuable source of potential molecular tools for understanding physiological processes for the development of new drugs. In this study two major PLA2s, named PLA2-I (Asp49) and PLA2-II (Lys49), isolated from the venom of Bothrops diporus from Northeastern Argentina, have shown cytotoxic effects on LM3 murine mammary tumor cells, with PLA2-II-like exhibiting a stronger effect compared to PLA2-I. At sub-cytotoxic levels, both PLA2s inhibited adhesion, migration, and invasion of these adenocarcinoma cells. Moreover, these toxins hindered tubulogenesis in endothelial cells, implicating a potential role in inhibiting tumor angiogenesis. All these inhibitory effects were more pronounced for the catalytically-inactive toxin. Additionally, in silico studies strongly suggest that this PLA2-II-like myotoxin could effectively block fibronectin binding to the integrin receptor, offering a dual advantage over PLA2-I in interacting with the αVß3 integrin. In conclusion, this study reports for the first time, integrating both in vitro and in silico approaches, a comparative analysis of the antimetastatic and antiangiogenic potential effects of two isoforms, an Asp49 PLA2-I and a Lys49 PLA2-II-like, both isolated from Bothrops diporus venom.

Breast cancer stem cells are involved in Trastuzumab resistance through the HER2 modulation in 3D culture.

Breast cancer human cells culture as spheroids develop autophagy and apoptosis, which promotes Trastuzumab resistance in HER2 overexpressing cells. Our aim was to study the association of the hostile environment developed in 3D with the breast cancer stem cells population and the HER2 modulation. Human mammary adenocarcinoma cell lines were cultured as spheroids using the hanging drop method. We generated hypoxia conditions by using a hypoxic chamber and CoCl2 treatment. Breast cancer stem cells were measured with mammosphere assays, the analysis of CD44 + CD24low population by flow cytometry and the pluripotent gene expression by RT-qPCR. HER2 expression was evaluated by flow cytometry and Western blot. MTS assays were conducted to study cell viability. Hostil environment developed in spheroids, defined by hypoxia and autophagy, modulated the response to Trastuzumab. In HER2+ cells with acquired resistance, we observed an increase in the breast cancer stem cell population. In BT474 spheroids, Trastuzumab induced the acquisition of resistance, along with an increase in breast cancer stem cells. Also, in 3D culture conditions we determined a modulation in the HER2 expression. Moreover, breast cancer stem cells showed enhanced HER2 expression. Finally, cells without HER2 gene amplification cultured as spheroids were sensitive to Trastuzumab, diminishing HER2 expression and cancer stem cells. Our findings show that 3D architecture is able to modulate breast cancer stem cell population and HER2 distribution, modifying the cell response to Trastuzumab.

N4 -aryl substituted thiosemicarbazones derived from 1-indanones as potential anti-tumor agents for breast cancer treatment.

Breast cancer is the first cause of cancer death in women. Many patients are resistant to current therapies, and even those were sensitive at first may eventually become resistant later. Thiosemicarbazones (TSCs) are synthetic compounds that exhibit several pharmacological activities. In this study, we investigated the potential anti-tumor activity of a set of N4 -arylsubstituted TSCs (N4 -TSCs) on human breast cancer cell lines. Studies on the effect of N4 -TSCs (T1, T2, and T3) were carried on MCF-7, MDA-MB 231, and BT 474 cell lines which differ in their expression of ER, PR, and Her2/neu. Non-transformed MCF-10A breast cell line were used as normal cells. Action of N4 -TSCs were evaluated by proliferation assay, quantification of apoptosis and cell cycle analysis. Modulation of clonogenic efficiency and migratory capacity by N4 -TSCs were also evaluated. We further investigated the effects of N4 -TSCs on ROS level and Ribonucleotide Reductase (RR) activity. We analyzed the action of these compounds on cellular mammosphere-forming capacity. We found that T1 and T2 had specific anti-tumor effect on all breast cancer cell lines based on their pro-apoptotic action and inhibitory effect on clonogenic efficiency and cell migration capacity. We also showed that both compounds increased ROS level and inhibited RR activity. Finally, we found that all N4 -TSCs diminished mammospehere-forming capacity of MCF-7 and BT 474 cells. N4 -TSCs showed specific anti-tumor action on human breast cancer cells independently their biomarkers expression pattern. Our results place these compounds as promising novel anti-tumor drugs with potential therapeutic application against different types of breast cancer.

Therapeutic blockade of Foxp3 in experimental breast cancer models.

PURPOSE: Regulatory T cells (Tregs) impair the clinical benefit of cancer immunotherapy. To optimize the antitumor efficacy of therapeutic dendritic cell (DC) vaccines, we aimed to inhibit Foxp3, a transcription factor required for Treg function. METHODS: Mice bearing established syngeneic LM3 and 4T1 breast tumors were treated with antitumor DC vaccines and a synthetic peptide (P60) that has been shown to inhibit Foxp3. RESULTS: Treatment with P60 improved the therapeutic efficacy of DC vaccines in these experimental models. In addition, monotherapy with P60 inhibited tumor growth in immunocompetent as well as in immuno-compromised animals bearing established tumors. We found expression of Foxp3 in human and murine breast tumor cells. P60 inhibited IL-10 secretion in breast cancer cells that expressed Foxp3. CONCLUSIONS: Our results suggest that Foxp3 blockade improves the therapeutic efficacy of DC vaccines by inhibition of Tregs and through a direct antitumor effect. This strategy could prove useful to neutralize the immunosuppressive microenvironment and to boost antitumor immunity in breast cancer.

Dual activation of Toll-like receptors 7 and 9 impairs the efficacy of antitumor vaccines in murine models of metastatic breast cancer.

PURPOSE: Since combination of Toll-like receptor (TLR) ligands could boost antitumor immunity, we evaluated the efficacy of dendritic cell (DC) vaccines upon dual activation of TLR9 and TLR7 in breast cancer models. METHODS: DCs were generated from mouse bone marrow or peripheral blood from healthy human donors and stimulated with CpG1826 (mouse TLR9 agonist), CpG2006 or IMT504 (human TLR9 agonists) and R848 (TLR7 agonist). Efficacy of antitumor vaccines was evaluated in BALB/c mice bearing metastatic mammary adenocarcinomas. RESULTS: CpG-DCs improved the survival of tumor-bearing mice, reduced the development of lung metastases and generated immunological memory. However, dual activation of TLRs impaired the efficacy of DC vaccines. In vitro, we found that R848 inhibited CpG-mediated maturation of murine DCs. A positive feedback loop in TLR9 mRNA expression was observed upon CpG stimulation that was inhibited in the presence of R848. Impaired activation of NF-κB was detected when TLR9 and TLR7 were simultaneously activated. Blockade of nitric oxide synthase (NOS) and indoleamine-pyrrole-2,3-dioxygenase (IDO) improved the activation of CpG-DCs. When we evaluated the effect of combined activation of TLR9 and TLR7 in human DCs, we found that R848 induced robust DC activation that was inhibited by TLR9 agonists. CONCLUSIONS: These observations provide insight in the biology of TLR9 and TLR7 crosstalk and suggest caution in the selection of agonists for multiple TLR stimulation. Blockade of NOS and IDO could improve the maturation of antitumor DC vaccines. R848 could prove a useful adjuvant for DC vaccines in human patients.

The synthetic peptide CIGB-300 modulates CK2-dependent signaling pathways affecting the survival and chemoresistance of non-small cell lung cancer cell lines.

BACKGROUND: Lung cancer is the most frequently diagnosed cancer and the leading cause of cancer-related deaths worldwide. Up to 80% of cancer patients are classified as non-small-cell lung cancer (NSCLC) and cisplatin remains as the gold standard chemotherapy treatment, despite its limited efficacy due to both intrinsic and acquired resistance. The CK2 is a Ser/Thr kinase overexpressed in various types of cancer, including lung cancer. CIGB-300 is an antitumor peptide with a novel mechanism of action, since it binds to CK2 substrates thus preventing the enzyme activity. The aim of this work was to analyze the effects of CIGB-300 treatment targeting CK2-dependent signaling pathways in NSCLC cell lines and whether it may help improve current chemotherapy treatment. METHODS: The human NSCLC cell lines NCI-H125 and NIH-A549 were used. Tumor spheroids were obtained through the hanging-drop method. A cisplatin resistant A549 cell line was obtained by chronic administration of cisplatin. Cell viability, apoptosis, immunoblotting, immunofluorescence and luciferase reporter assays were used to assess CIGB-300 effects. A luminescent assay was used to monitor proteasome activity. RESULTS: We demonstrated that CIGB-300 induces an anti-proliferative response both in monolayer- and three-dimensional NSCLC models, presenting rapid and complete peptide uptake. This effect was accompanied by the inhibition of the CK2-dependent canonical NF-κB pathway, evidenced by reduced RelA/p65 nuclear levels and NF-κB protein targets modulation in both lung cancer cell lines, as well as conditionally reduced NF-κB transcriptional activity. In addition, NF-κB modulation was associated with enhanced proteasome activity, possibly through its α7/C8 subunit. Neither the peptide nor a classical CK2 inhibitor affected cytoplasmic ß-CATENIN basal levels. Given that NF-κB activation has been linked to cisplatin-induced resistance, we explored whether CIGB-300 could bring additional therapeutic benefits to the standard cisplatin treatment. We established a resistant cell line that showed higher p65 nuclear levels after cisplatin treatment as compared with the parental cell line. Remarkably, the cisplatin-resistant cell line became more sensitive to CIGB-300 treatment. CONCLUSIONS: Our data provide new insights into CIGB-300 mechanism of action and suggest clinical potential on current NSCLC therapy.

The Immune System As a New Possible Cell Target for AFP 464 in a Spontaneous Mammary Cancer Mouse Model.

Aminoflavone (AFP 464, NSC 710464), an antitumor agent which recently entered phase II clinical trials, acts against estrogen-positive breast cancer (ER+). AFP 464, which has a unique mechanism of action by activating aryl hydrocarbon receptor (AhR) signaling pathway, decreased tumor size, and growth rate in the estrogen dependent, Tamoxifen-sensitive spontaneous M05 mouse model. Considering that AhR has recently emerged as a physiological regulator of the innate and adaptive immune responses, we investigated whether AFP 464 modulates the immune response in our mouse model. Studies on the effect of AFP 464 on the immune system were carried in BALB/c mice bearing M05 semi-differentiated mammary adenocarcinomas that express estrogen and progesterone receptors. Splenic cells and tumor inflammatory infiltrates were studied by cytometric analyses. The modulation of splenocytes cytotoxic activity by AFP 464 was also evaluated. We further investigated the effects of AFP 464 on peritoneal macrophages by evaluating metalloproteinase, arginase, and iNOS activities. We found that AFP 464 increased splenic cytotoxic activity, diminished the number of systemic and local Treg lymphocytes, and MDSCs, and induced a M1 phenotype in peritoneal macrophages of M05 tumor bearing mice. Therefore, we conclude that AFP 464 modulates immune response which collaborates with its anti-tumor activity. Our results place the immune system as a novel target for this anti-cancer agent to strengthen the rationale for its inclusion in breast cancer treatment regimens. J. Cell. Biochem. 118: 2841-2849, 2017. © 2017 Wiley Periodicals, Inc.

Glypican-3 induces a mesenchymal to epithelial transition in human breast cancer cells.

Breast cancer is the disease with the highest impact on global health, being metastasis the main cause of death. To metastasize, carcinoma cells must reactivate a latent program called epithelial-mesenchymal transition (EMT), through which epithelial cancer cells acquire mesenchymal-like traits.Glypican-3 (GPC3), a proteoglycan involved in the regulation of proliferation and survival, has been associated with cancer. In this study we observed that the expression of GPC3 is opposite to the invasive/metastatic ability of Hs578T, MDA-MB231, ZR-75-1 and MCF-7 human breast cancer cell lines. GPC3 silencing activated growth, cell death resistance, migration, and invasive/metastatic capacity of MCF-7 cancer cells, while GPC3 overexpression inhibited these properties in MDA-MB231 tumor cell line. Moreover, silencing of GPC3 deepened the MCF-7 breast cancer cells mesenchymal characteristics, decreasing the expression of the epithelial marker E-Cadherin. On the other side, GPC3 overexpression induced the mesenchymal-epithelial transition (MET) of MDA-MB231 breast cancer cells, which re-expressed E-Cadherin and reduced the expression of vimentin and N-Cadherin. While GPC3 inhibited the canonical Wnt/ß-Catenin pathway in the breast cancer cells, this inhibition did not have effect on E-Cadherin expression. We demonstrated that the transcriptional repressor of E-Cadherin - ZEB1 - is upregulated in GPC3 silenced MCF-7 cells, while it is downregulated when GPC3 was overexpressed in MDA-MB231 cells. We presented experimental evidences showing that GPC3 induces the E-Cadherin re-expression in MDA-MB231 cells through the downregulation of ZEB1.Our data indicate that GPC3 is an important regulator of EMT in breast cancer, and a potential target for procedures against breast cancer metastasis.

Autophagy Protects from Trastuzumab-Induced Cytotoxicity in HER2 Overexpressing Breast Tumor Spheroids.

Multicellular tumor spheroids represent a 3D in vitro model that mimics solid tumor essential properties including assembly and development of extracellular matrix and nutrient, oxygen and proliferation gradients. In the present study, we analyze the impact of 3D spatial organization of HER2-overexpressing breast cancer cells on the response to Trastuzumab. We cultured human mammary adenocarcinoma cell lines as spheroids with the hanging drop method and we observed a gradient of proliferating, quiescent, hypoxic, apoptotic and autophagic cells towards the inner core. This 3D organization decreased Trastuzumab sensitivity of HER2 over-expressing cells compared to monolayer cell cultures. We did not observe apoptosis induced by Trastuzumab but found cell arrest in G0/G1 phase. Moreover, the treatment downregulated the basal apoptosis only found in tumor spheroids, by eliciting protective autophagy. We were able to increase sensitivity to Trastuzumab by autophagy inhibition, thus exposing the interaction between apoptosis and autophagy. We confirmed this result by developing a resistant cell line that was more sensitive to autophagy inhibition than the parental BT474 cells. In summary, the development of Trastuzumab resistance relies on the balance between death and survival mechanisms, characteristic of 3D cell organization. We propose the use of spheroids to further improve the understanding of Trastuzumab antitumor activity and overcome resistance.

Myoepithelial and luminal breast cancer cells exhibit different responses to all-trans retinoic acid.

PURPOSE: Breast cancer is the leading cause of death among women worldwide. The exact role of luminal epithelial (LEP) and myoephitelial (MEP) cells in breast cancer development is as yet unclear, as also how retinoids may affect their behaviour. Here, we set out to evaluate whether retinoids may differentially regulate cell type-specific processes associated with breast cancer development using the bi-cellular LM38-LP murine mammary adenocarcinoma cell line as a model. MATERIALS AND METHODS: The bi-cellular LM38-LP murine mammary cell line was used as a model throughout all experiments. LEP and MEP subpopulations were separated using inmunobeads, and the expression of genes known to be involved in epithelial to mysenchymal transition (EMT) was assessed by qPCR after all-trans retinoic acid (ATRA) treatment. In vitro invasive capacities of LM38-LP cells were evaluated using 3D Matrigel cultures in conjunction with confocal microscopy. Also, in vitro proliferation, senescence and apoptosis characteristics were evaluated in the LEP and MEP subpopulations after ATRA treatment, as well as the effects of ATRA treatment on the clonogenic, adhesive and invasive capacities of these cells. Mammosphere assays were performed to detect stem cell subpopulations. Finally, the orthotopic growth and metastatic abilities of LM38-LP monolayer and mammosphere-derived cells were evaluated in vivo. RESULTS: We found that ATRA treatment modulates a set of genes related to EMT, resulting in distinct gene expression signatures for the LEP or MEP subpopulations. We found that the MEP subpopulation responds to ATRA by increasing its adhesion to extracellular matrix (ECM) components and by reducing its invasive capacity. We also found that ATRA induces apoptosis in LEP cells, whereas the MEP compartment responded with senescence. In addition, we found that ATRA treatment results in smaller and more organized LM38-LP colonies in Matrigel. Finally, we identified a third subpopulation within the LM38-LP cell line with stem/progenitor cell characteristics, exhibiting a partial resistance to ATRA. CONCLUSIONS: Our results show that the luminal epithelial (LEP) and myoephitelial (MEP) mammary LM38-P subpopulations respond differently to ATRA, i.e., the LEP subpopulation responds with increased cell cycle arrest and apoptosis and the MEP subpopulation responds with increased senescence and adhesion, thereby decreasing its invasive capacity. Finally, we identified a third subpopulation with stem/progenitor cell characteristics within the LM38-LP mammary adenocarcinoma cell line, which appears to be non-responsive to ATRA.

Differential response of myeloid-derived suppressor cells to the nonsteroidal anti-inflammatory agent indomethacin in tumor-associated and tumor-free microenvironments.

Myeloid-derived suppressor cells (MDSCs) are key regulatory cells that control inflammation and promote tumor-immune escape. To date, no specific immunomodulatory drug has proven efficacy in targeting the expansion and/or function of these cells in different pathophysiologic settings. In this study, we identified a context-dependent effect of the nonsteroidal anti-inflammatory drug indomethacin (IND) on MDSCs, depending on whether they were derived from tumor microenvironments (TME) or from tumor-free microenvironments (TFME). Treatment of mice bearing the LP07 lung adenocarcinoma with IND inhibited the suppressive activity of splenic MDSCs, which restrained tumor growth through mechanisms involving CD8(+) T cells. The same effect was observed when MDSCs were treated with IND and conditioned media from LP07 tumor cells in vitro. However, in the absence of a tumor context, IND enhanced the intrinsic suppressive function of MDSCs and amplified their protumoral activity. In a model of autoimmune neuroinflammation, IND-treated MDSCs differentiated in TFME attenuated inflammation, whereas IND-treated MDSCs differentiated in TME aggravated clinical symptoms and delayed resolution of the disease. Mechanistically, IND reduced arginase activity as well as NO and reactive oxygen species production in MDSCs differentiated in TME but not in TFME. Moreover, expression of the C/EBP-ß transcription factor isoforms correlated with the suppressive activity of IND-treated MDSCs. Our study unveils the dual and context-dependent action of IND, a drug that serves both as an anti-inflammatory and anticancer agent, which differentially affects MDSC activity whether these cells are derived from TME or TFME. These results have broad clinical implication in cancer, chronic inflammation and autoimmunity.

Hypoxia-induced nitric oxide release by luminal cells stimulates proliferation and uPA secretion of myoepithelial cells in a bicellular murine mammary tumor.

INTRODUCTION: LM38 murine mammary adenocarcinoma model is formed by LM38-LP (myoepithelial and luminal), LM38-HP (luminal) and LM38-D2 (myoepithelial) cell lines. In a previous work, we had shown that LM38-HP and LM38-D2 cell lines are less malignant than the bicellular LM38-LP cell line. PURPOSE: To study the role of nitric oxide (NO) as one of the mediators of functional interactions between malignant luminal and myoepithelial cells. METHODS AND RESULTS: Using immunohistochemistry, in vivo iNOS expression was only detected in the luminal cells of bicellular LM38-LP and most cells of LM38-HP tumors. In cobalt-induced pseudohypoxia, LM38-LP and LM38-HP cell lines significantly increased HIF-1α and iNOS expression (Western blotting) and therefore NO production (Griess method). This increase was inhibited by the iNOS inhibitor 1400 W. On the other side, NO was not detectable in LM38-D2 cells either in basal or in pseudohypoxia. In addition, pseudohypoxia increased urokinase-type plasminogen activator (uPA) secretion by LM38-LP and LM38-HP cells and migration in the LM38-LP cell line, without modulating these properties in LM38-D2 cells (radial caseinolysis). The NO donor DETA/NONOate (500 µM) was able to increase uPA secretion and in vitro growth of LM38-D2. In agreement, 1400 W prevented in vivo growth of the myoepithelial LM38-D2 cells. CONCLUSIONS: Hypoxia leads to an enhanced NO production by the luminal component, through HIF-1α and iNOS, which can stimulate myoepithelial cell proliferation and uPA secretion. In these new conditions, myoepithelial cells might act as an invasive forefront generating gaps that could help luminal cells to escape from the primary tumor.

Oral-specific ablation of Klf4 disrupts epithelial terminal differentiation and increases premalignant lesions and carcinomas upon chemical carcinogenesis.

BACKGROUND: Squamous cell carcinoma (SSC) of the head and neck is the sixth most common cancer and is rarely diagnosed in early stages. The transcription factor Krϋppel-like factor 4 (Klf4) suppresses cell proliferation and promotes differentiation. Inducible mice carrying an oral-specific ablation of Klf4 (K14-CreER(tam) /Klf4(flox/flox) ) develop mild dysplastic lesions and abnormal differentiation in the tongue. Aiming to analyze whether Klf4 cooperate in oral chemical carcinogenesis,we applied 4-nitroquinoline 1-oxide (4NQO), a tobacco surrogate, to this conditional Klf4 knockout mice. METHODS: K14-CreER(tam) /Klf4(flox/flox) and control mice were treated with 4NQO for 16 weeks and monitored until week 30. Histopathological samples were used for diagnostic purposes and immunofluorescence detection of epithelial differentiation markers. RESULTS: 4NQO-treated K14-CreER(tam) /Klf4(flox/flox) mice (Klf4KO 4NQO) showed a significant weight loss and developed more severe dysplastic lesions than control mice with 4NQO (P < 0.005). The Klf4KO 4NQO showed a tendency to higher incidence of oral SCC and a marked keratinization pattern in dysplasias, in situ carcinomas and SCC. Also, tongues derived from Klf4KO 4NQO mice exhibited reduced terminal differentiation as judged by cytokeratin 1 staining when compared with 4NQO-treated controls. CONCLUSIONS: Klf4 ablation results in more severe dysplastic lesions in oral mucosa, with a tendency to higher incidence of SCC, after chemical carcinogenesis. We show here, in a context similar to the human carcinogenesis, that absence of Klf4 accelerates carcinogenesis and correlates with the absence of cytokeratin 1 expression. These results suggest a potential role for KLF4 as a tumor suppressor gene for the tongue epithelium.

Non-genomic actions of estradiol and 4-OH-tamoxifen on murine breast cancer cells.

Estrogens and tamoxifen do not only exert their effects at the genomic level, but also play a role at the cell membrane activating downstream signaling pathways. We recently characterized an estrogen receptor-positive epithelial murine breast cancer cell line, LM05-E. Utilizing this cell line and MCF-7 cells, we compared the non-genomic effects of estradiol and 4-OH-tamoxifen. We showed that, similar to estradiol, tamoxifen activated the MAPK/ERK 1/2 pathway; however, we did not find activation of PI3K/AKT by either estradiol or tamoxifen. Short-term treatments with estradiol stimulated, whereas tamoxifen inhibited cell proliferation. Using pharmacological inhibitors we showed that the effect of estradiol was mediated by the MAPK/ERK 1/2 pathway, but that inhibition of this pathway did not affect tamoxifen. Surprisingly, however, blocking of PI3K/AKT signaling interfered with the inhibitory effect of tamoxifen. Analysis of the involvement of the EGFR support previous findings that designate this receptor as a mediator of the non-genomic effects of estradiol; blocking EGFR also reverses the inhibitory effect of tamoxifen. Finally, matrix metalloproteinases (MMPs) were confirmed to be involved in the proliferative effect of estradiol. These results demonstrated the novel non-genomic effects of tamoxifen and revealed that pathways downstream of EGFR and PI3K/AKT are involved in the inhibition of cell proliferation. Caution should be exercised when analyzing strategies that aim at combining endocrine therapy with specific signaling inhibitors.

Involvement of protein kinase C α and δ activities on the induction of the retinoic acid system in mammary cancer cells.

It has been established that retinoids exert some of their effects on cell differentiation and malignant phenotype reversion through the interaction with different members of the protein kinase C (PKC) family. Till nowadays the nature and extension of this interaction is not well understood. Due to the cytostatic and differentiating effects of retinoids, in the present study we propose to evaluate whether the crosstalk between the retinoid system and the PKC pathway could become a possible target for breast cancer treatment. We could determine that ATRA (all-trans retinoic) treatment showed a significant growth inhibition due to (G1 or G2) cell cycle arrest both in LM3 and SKBR3, a murine and human mammary cell line respectively. ATRA also induced a remarkable increase in PKCα and PKCδ expression and activity. Interestingly, the pharmacological inhibition of these two PKC isoforms prevented the activation of retinoic acid receptors (RARs) by ATRA, indicating that both PKC isoforms are required for RARs activation. Moreover, PKCδ inhibition also impaired ATRA-induced RARα translocation to the nucleus. In vivo assays revealed that a combined treatment using ATRA and PKCα inhibitors prevented lung metastatic dissemination in an additive way. Our results clearly indicate that ATRA modulates the expression and activity of different PKCs. Besides inducing cell arrest, the activity of both PKC is necessary for the induction of the retinoic acid system. The combined ATRA and PKCα inhibitors could be an option for the hormone-independent breast cancer treatment.

The rigid steroid 21-hydroxy-6,19-epoxyprogesterone (21OH-6,19OP) is a dissociated glucocorticoid receptor modulator potentially useful as a novel coadjuvant in breast cancer chemotherapy.

Glucocorticoids (GCs) are steroid hormones widely used as coadjuvants in the treatment of solid tumors due to their anti-inflammatory effects. However, evidence show that they also may induce chemotherapy resistance, probably through their capacity to inhibit apoptosis triggered by antineoplastic drugs. GCs exert their action by regulating gene expression throughout two main mechanisms: transactivation, where the activated glucocorticoid receptor (GR) directly binds to certain genes; and transrepression, an indirect mechanism by which GR regulates other transcription factors activities. Recently, our group has shown that the rigid steroid 21-hydroxy-6,19-epoxyprogesterone (21OH-6,19OP) is a selective GR ligand that behaves as an agonist in transrepression assays and as an antagonist in transactivation ones. Here, we have evaluated the anti-inflammatory activity of 21OH-6,19OP, its capacity to generate chemoresistance, as well as its mechanism of action. We found that 21OH-6,19OP inhibits nitrites formation and the inducible nitric oxide synthase (Nos-2) expression in macrophages. It also blocks the expression of both cyclooxygenase-2 (COX-2) and interleukin-8 (IL-8) triggered by tumor necrosis factor-alpha (TNF-α) in epithelial lung cancer cells. However, contrary to dexamethasone (DEX), 21OH-6,19OP neither reverts the paclitaxel-induced caspase-3 activity, nor induces the anti-apoptotic Bcl-X(L) gene expression in murine tumor mammary epithelial cells; and importantly, it lacks GCs-associated chemoresistance in a mouse mammary tumor model. Together, our findings suggest that 21OH-6,19OP behaves as a dissociated GC that keeps anti-inflammatory action without affecting the apoptotic process triggered by chemotherapeutic drugs. For these reasons, this steroid may become a putative novel coadjuvant in the treatment of breast cancer.

Impairing squamous differentiation by Klf4 deletion is sufficient to initiate tongue carcinoma development upon K-Ras activation in mice.

Oral squamous cell carcinoma (SCC) is among the most prevalent cancers in the world and is characterized by high morbidity and few therapeutic options. Like most cancers, oral SCC arises from a multistep process involving alterations of genes responsible for balancing proliferation and differentiation. Among these, Krϋppel-like factor 4 (Klf4) suppresses cell proliferation and promotes differentiation and thus helps to maintain epithelial homeostasis. However, the prevailing role of Klf4 in maintenance of normal homeostasis in oral epithelium has not been established in vivo. Here, we used an inducible oral-specific mice model to selectively ablate Klf4 in the oral cavity. We generated K14-CreER(Tam)/Klf4 (f/f) mice that survived to adulthood and did not present overt phenotype. However, histologically these mice showed dysplastic lesions, increased cell proliferation and abnormal differentiation in the tongue 4 months after induction, supporting a homeostatic role of Klf4 in the oral epithelia. Furthermore, by breeding these mutants with a transgenic line expressing at endogenous levels K-ras (G12D), we assessed the role of disrupting differentiation gene programs to the carcinogenesis process. The K14-CreER(TAM)/K-ras (G12D)/Klf4 (-) (/-) mice rapidly develop oral SCC in the tongue. Thus, our findings support the emerging notion that activation of differentiating gene programs may represent a barrier preventing carcinogenesis in epithelial cells harboring oncogenic mutations, and thus that molecules acting upstream and downstream of Klf4 may represent components of a novel tumor-suppressive pathway.

TGF-beta specifically enhances the metastatic attributes of murine lung adenocarcinoma: implications for human non-small cell lung cancer.

Lung cancer is the most frequent and one of the most deadly cancer types and is classified into small cell lung cancer and non-small cell lung cancer (NSCLC). Transforming growth factor beta (TGFß) regulates a wide array of cell functions and plays a major role in lung diseases, including NSCLC. TGFß signals through the complex of TGFß type I and type II receptors, triggering Smad and non-Smad signaling pathways such as PI3K/Akt and MEK1/ERK. We investigated the role of TGFß1 on the progression of the murine lung adenocarcinoma cell line LP07. Furthermore, we undertook a retrospective study with tissue samples from stage I and II NSCLC patients to assess the clinical pathologic role and prognostic significance of TßRI expression. We demonstrated that although lung cancer cell monolayers responded to TGFß1 anti-mitogenic effects and TGFß1 pulse (24 h treatment) delayed tumor growth at primary site; a switch towards malignant progression upon TGFß1 treatment was observed at the metastatic site. In our model, TGFß1 modulated in vitro clonogenicity, protected against stress-induced apoptosis and increased adhesion, spreading, lung retention and metastatic outgrowth. PI3K and MEK1 signaling pathways were involved in TGFß1-mediated metastasis stimulation. Several of these TGFß responses were also observed in human NSCLC cell lines. In addition, we found that a higher expression of TßRI in human lung tumors is associated with poor patient's overall survival by univariate analysis, while multivariate analysis did not reach statistical significance. Although additional detailed analysis of the endogenous signaling in vivo and in vitro is needed, these studies may provide novel molecular targets for the treatment of lung cancer.

Modulation of pancreatic tumor potential by overexpression of protein kinase C ß1.

OBJECTIVE: This study aimed to investigate whether the overexpression of protein kinase C ß1 (PKCß1) is able to modulate the malignant phenotype displayed by the human ductal pancreatic carcinoma cell line PANC1. METHODS: PKCß1 overexpression was achieved using a stable transfection approach. PANC1-PKCß1 and control cells were analyzed both in vitro and in vivo. RESULTS: PANC1-PKCß1 cells displayed a lower growth capacity associated with the down-regulation of the MEK/ERK pathway and cyclin expression. Furthermore, PKCß1 overexpression was associated with an enhancement of cell adhesion to fibronectin and with reduced migratory and invasive phenotypes. In agreement with these results, PANC1-PKCß1 cells showed an impaired ability to secrete proteolytic enzymes. We also found that PKCß1 overexpressing cells were more resistant to cell death induced by serum deprivation, an event associated with G0/G1 arrest and the modulation of PI3K/Akt and NF-κB pathways. Most notably, the overexpression of PKCß1 completely abolished the ability of PANC1 cells to induce tumors in nude mice. CONCLUSIONS: Our results established an important role for PKCß1 in PANC1 cells suggesting it would act as a suppressor of tumorigenic behavior in pancreatic cancer.

A clinically relevant bi-cellular murine mammary tumor model as a useful tool for evaluating the effect of retinoic acid signaling on tumor progression.

BACKGROUND: The effect of retinoic acid (RA) on breast cancer progression is controversial. Our objective was to obtain information about breast cancer progression, taking advantage of the ER-negative murine mammary adenocarcinoma model LM38 (LM38-LP constituted by luminal (LEP) and myoepithelial-like cells (MEP), LM38-HP mainly composed of spindle-shaped epithelial cells, and LM38-D2 containing only large myoepithelial cells), and to validate the role of the retinoic acid receptors (RARs) in each cell-type compartment. MATERIALS AND METHODS: We studied the expression and functionality of the RARs in LM38 cell lines. We analyzed cell growth and cell cycle distribution, apoptosis, the activity of proteases, motility properties, and expression of the molecules involved in these pathways. We also evaluated tumor growth and dissemination in vivo under retinoid treatment. RESULTS: LM38 cell lines expressed most retinoic receptor isotypes that were functional. However, only the bi-cellular LM38-LP cells responded to retinoids by increasing RARß2 and CRBP1 expression. The growth of LM38 cell sublines was inhibited by retinoids, first by inducing arrest in MEP cells, then apoptosis in LEP cells. Retinoids induced inhibitory effects on motility, invasiveness, and activity of proteolytic enzymes, mainly in the LM38-LP cell line. In in-vivo assays with the LM38-LP cell line, RA treatment impaired both primary tumor growth and lung metastases dissemination. CONCLUSION: These in-vivo and in-vitro results show that to achieve maximum effects of RA on tumor progression both the LEP and MEP cell compartments have to be present, suggesting that the interaction between the LEP and MEP cells is crucial to full activation of the RARs.