Effective combination treatments for breast cancer inhibition by FOXM1 inhibitors with other targeted cancer drugs.

PURPOSE: Few targeted treatment options currently exist for patients with advanced, often recurrent breast cancers, both triple-negative breast cancer (TNBC) and hormone receptor-positive breast cancer. Forkhead box M1 (FOXM1) is an oncogenic transcription factor that drives all cancer hallmarks in all subtypes of breast cancer. We previously developed small-molecule inhibitors of FOXM1 and to further exploit their potential as anti-proliferative agents, we investigated combining FOXM1 inhibitors with drugs currently used in the treatment of breast and other cancers and assessed the potential for enhanced inhibition of breast cancer. METHODS: FOXM1 inhibitors alone and in combination with other cancer therapy drugs were assessed for their effects on suppression of cell viability and cell cycle progression, induction of apoptosis and caspase 3/7 activity, and changes in related gene expressions. Synergistic, additive, or antagonistic interactions were evaluated using ZIP (zero interaction potency) synergy scores and the Chou-Talalay interaction combination index. RESULTS: The FOXM1 inhibitors displayed synergistic inhibition of proliferation, enhanced G2/M cell cycle arrest, and increased apoptosis and caspase 3/7 activity and associated changes in gene expression when combined with several drugs across different pharmacological classes. We found especially strong enhanced effectiveness of FOXM1 inhibitors in combination with drugs in the proteasome inhibitor class for ER-positive and TNBC cells and with CDK4/6 inhibitors (Palbociclib, Abemaciclib, and Ribociclib) in ER-positive cells. CONCLUSION: The findings suggest that the combination of FOXM1 inhibitors with several other drugs might enable dose reduction in both agents and provide enhanced efficacy in treatment of breast cancer.

Estrogen Receptor Beta 1: A Potential Therapeutic Target for Female Triple Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer characterized by the absence of estrogen receptor alpha, progesterone receptor, and HER2. These receptors often serve as targets in breast cancer treatment. As a result, TNBCs are difficult to treat and have a high propensity to metastasize to distant organs. For these reasons, TNBCs are responsible for over 50% of all breast cancer mortalities while only accounting for 15% to 20% of breast cancer cases. However, estrogen receptor beta 1 (ERß1), an isoform of the ESR2 gene, has emerged as a potential therapeutic target in the treatment of TNBCs. Using an in vivo xenograft preclinical mouse model with human TNBC, we found that expression of ERß1 significantly reduced both primary tumor growth and metastasis. Moreover, TNBCs with elevated levels of ERß1 showed reduction in epithelial to mesenchymal transition markers and breast cancer stem cell markers, and increases in the expression of genes associated with inhibition of cancer cell invasiveness and metastasis, suggesting possible mechanisms underlying the antitumor activity of ERß1. Gene expression analysis by quantitative polymerase chain reaction and RNA-seq revealed that treatment with chloroindazole, an ERß-selective agonist ligand, often enhanced the suppressive activity of ERß1 in TNBCs in vivo or in TNBC cells in culture, suggesting the potential utility of ERß1 and ERß ligand in improving TNBC treatment. The findings enable understanding of the mechanisms by which ERß1 impedes TNBC growth, invasiveness, and metastasis and consideration of ways by which treatments involving ERß might improve TNBC patient outcome.

Contrasting activities of estrogen receptor beta isoforms in triple negative breast cancer.

PURPOSE: Triple negative breast cancer (TNBC), an aggressive subtype of breast cancer, lacks the three major receptors for predicting outcome or targeting therapy. Hence, our aim was to evaluate the potential of estrogen receptor beta (ERß) as a possible endocrine therapy target in TNBC. METHODS: The expression and prognostic effect of ERß isoforms were analyzed using TCGA breast tumor data, and the expression of ERß isoform mRNA and protein in TNBC cell lines was assayed. Endogenous ERß2 and ERß5 were knocked down with siRNA, and ERß2, ERß5, and ERß1 were upregulated using a doxycycline-inducible lentiviral system. Cell proliferation, migration and invasion, and specific gene expressions were evaluated. RESULTS: ERß2 and ERß5 were the predominant endogenous forms of ERß in TNBC tumors and cell lines. High ERß2 predicted worse clinical outcome. Knockdown of endogenous ERß2/ERß5 in cell lines suppressed proliferation, migration and invasion, and downregulated proto-oncogene survivin expression. ERß2/ERß5 upregulation did the reverse, increasing survivin and these cell activities. ERß1 was barely detectable in TNBC cell lines, but its upregulation reduced survivin, increased tumor suppressor expression (E-cadherin and cystatins), and suppressed proliferation, migration and invasion in both ligand-independent and dependent manners, suggesting the possible translational benefit of ERß ligands. CONCLUSIONS: ERß2/ERß5 and ERß1 exhibit sharply contrasting activities in TNBC cells. Our findings imply that delineating the absolute amounts and relative ratios of the different ERß isoforms might have prognostic and therapeutic relevance, and could enable better selection of optimal approaches for treatment of this often aggressive form of breast cancer.

Suppression of Tumor Growth, Metastasis, and Signaling Pathways by Reducing FOXM1 Activity in Triple Negative Breast Cancer.

Metastasis-related complications account for the overwhelming majority of breast cancer mortalities. Triple negative breast cancer (TNBC), the most aggressive breast cancer subtype, has a high propensity to metastasize to distant organs, leading to poor patient survival. The forkhead transcription factor, FOXM1, is especially upregulated and overexpressed in TNBC and is known to regulate multiple signaling pathways that control many key cancer properties, including proliferation, invasiveness, stem cell renewal, and therapy resistance, making FOXM1 a critical therapeutic target for TNBC. In this study, we test the effectiveness of a novel class of 1,1-diarylethylene FOXM1 inhibitory compounds in suppressing TNBC cell migration, invasion, and metastasis using in vitro cell culture and in vivo tumor models. We show that these compounds inhibit the motility and invasiveness of TNBC MDA-MB-231 and DT28 cells, along with reducing the expression of important epithelial to mesenchymal transition (EMT) associated genes. Further, orthotopic tumor studies in NOD-SCID-gamma (NSG) mice demonstrate that these compounds reduce FOXM1 expression and suppress TNBC tumor growth as well as distant metastasis. Gene expression and protein analyses confirm the decreased levels of EMT factors and FOXM1-regulated target genes in tumors and metastatic lesions in the inhibitor-treated animals. The findings suggest that these FOXM1 suppressive compounds may have therapeutic potential in treating triple negative breast cancer, with the aim of reducing tumor progression and metastatic outgrowth.

Suppression of breast cancer metastasis and extension of survival by a new antiestrogen in a preclinical model driven by mutant estrogen receptors.

PURPOSE: Many human breast tumors become resistant to endocrine therapies and recur due to estrogen receptor (ERα) mutations that convey constitutive activity and a more aggressive phenotype. Here, we examined the effectiveness of a novel adamantyl antiestrogen, K-07, in suppressing the growth of breast cancer metastases containing the two most frequent ER-activating mutations, Y537S and D538G, and in extending survival in a preclinical metastatic cancer model. METHODS: MCF7 breast cancer cells expressing luciferase and Y537S or D538G ER were injected into NOD-SCID-gamma female mice, and animals were treated orally with the antiestrogen K-07 or control vehicle. Comparisons were also made with the antiestrogen Fulvestrant. The development of metastases was monitored by in vivo bioluminescence imaging with phenotypic characterization of the metastases in liver and lung by immunohistochemical and biochemical analyses. RESULTS: These breast cancer cells established metastases in liver and lung, and K-07 treatment reduced the metastatic burden. Mice treated with K-07 also survived much longer. By day 70, only 28% of vehicle-treated mice with mutant ER metastases were alive, whereas all K-07-treated D538G and Y537S mice were still alive. K-07 also markedly reduced the level of metastatic cell ER and the expression of ER-regulated genes. CONCLUSION: The antiestrogen K-07 can reduce in vivo metastasis of breast cancers and extend host survival in this preclinical model driven by constitutively active mutant ERs, suggesting that this compound may be suitable for further translational examination of its efficacy in suppression of metastasis in breast cancers containing constitutively active mutant ERs.

Suppression of FOXM1 activities and breast cancer growth in vitro and in vivo by a new class of compounds.

The transcription factor FOXM1 is upregulated and overexpressed in aggressive, therapy-resistant forms of hormone receptor-positive and triple negative breast cancers, and is associated with less good patient survival. FOXM1 signaling is also a key driver in many other cancers. Here, we identify a new class of compounds effective in suppressing FOXM1 activity in breast cancers, and displaying good potency for antitumor efficacy. The compounds bind directly to FOXM1 and alter its proteolytic sensitivity, reduce the cellular level of FOXM1 protein by a proteasome- dependent process, and suppress breast cancer cell proliferation and cell cycle progression and increase apoptosis. RNA-seq and gene set enrichment analyses indicate that the compounds decrease expression of FOXM1-regulated genes and suppress gene ontologies under FOXM1 regulation. Several compounds have favorable pharmacokinetic properties and show good tumor suppression in preclinical breast tumor models. These compounds may be suitable for further clinical evaluation in targeting aggressive breast cancers driven by FOXM1.

Direct electrochemical reduction of hematite decorated graphene oxide (α-Fe2O3@erGO) nanocomposite for selective detection of Parkinson's disease biomarker.

An unusual approach is reported herein to fabricate magnetic hematite (α-Fe2O3) decorated electrochemically reduced graphene oxide (α-Fe2O3@erGO) nanocomposite. The method utilizes direct electrochemical reduction of self-assembled, ex-situ synthesized α-Fe2O3 anchored GO to erGO (α-Fe2O3@erGO) on glassy carbon electrode (GCE) for selective detection dopamine (DA), an important biomarker of Parkinson's disease. The formation of α-Fe2O3@erGO/GCE has been confirmed by XPS and Raman spectroscopy. α-Fe2O3@erGO modified GCE exhibits synergistic catalytic activity nearly 2.2 and 5 fold higher than α-Fe2O3@GO and other modified electrodes, respectively towards oxidation of DA. The fabricated sensor exhibited linear dynamic ranges over 0.25 - 100 µM in response to DA with a LOD of 0.024 µM (S/N = 3), LOQ of 0.08 µM (S/N = 10), and a sensitivity of 12.56 µA µM-1 cm-2. Finally, the practical analytical application of the proposed α-Fe2O3@erGO/GCE was investigated for the determination of DA in commercially available pharmaceutical formulation and human serum samples, and showed satisfactory recovery results towards DA.

PD2/PAF1 at the Crossroads of the Cancer Network.

Pancreatic differentiation 2 (PD2)/RNA polymerase II-associated factor 1 (PAF1) is the core subunit of the human PAF1 complex (PAF1C) that regulates the promoter-proximal pausing of RNA polymerase II as well as transcription elongation and mRNA processing and coordinates events in mRNA stability and quality control. As an integral part of its transcription-regulatory function, PD2/PAF1 plays a role in posttranslational histone covalent modifications as well as regulates expression of critical genes of the cell-cycle machinery. PD2/PAF1 alone, and as a part of PAF1C, provides distinct roles in the maintenance of self-renewal of embryonic stem cells and cancer stem cells, and in lineage differentiation. Thus, PD2/PAF1 malfunction or its altered abundance is likely to affect normal cellular functions, leading to disease states. Indeed, PD2/PAF1 is found to be upregulated in poorly differentiated pancreatic cancer cells and has the capacity for neoplastic transformation when ectopically expressed in mouse fibroblast cells. Likewise, PD2/PAF1 is upregulated in pancreatic and ovarian cancer stem cells. Here, we concisely describe multifaceted roles of PD2/PAF1 associated with oncogenic transformation and implicate PD2/PAF1 as an attractive target for therapeutic development to combat malignancy. Cancer Res; 78(2); 313-9. ©2018 AACR.

Overexpression of PD2 leads to increased tumorigenicity and metastasis in pancreatic ductal adenocarcinoma.

Pancreatic differentiation 2 (PD2), an important subunit of the human PAF complex, was identified after differential screening analysis of 19q13 amplicon, and its overexpression induces oncogenic transformation of NIH3T3 cells, hence raising the possibility of a role for PD2 in tumorigenesis and metastasis. To test this hypothesis, we analyzed here the functional role and clinical significance of PD2 in pancreatic ductal adenocarcinoma (PDAC) and its pathogenesis. Using immunohistochemical analysis, we found that PD2 is detected in the acini but not in the ducts in the normal pancreas. In human PDAC specimens, PD2 was instead primarily detected in the ducts (12/48 patients 25%; p-value < 0.0001), thereby showing that PDAC correlates with increased ductal expression of PD2. Consistently, PD2 expression was increased in telomerase-immortalized human pancreatic ductal cells (HPNE cells) modified to express the HPV16 E6 and E7 proteins, whose respective functions are to block p53 and RB. In addition, ectopic expression of PD2 in PDAC cells (Capan-1 and SW1990) led to increased clonogenicity and migration in vitro, and tumor growth and metastasis in vivo. Interestingly, PD2 overexpression also resulted in enrichment of cancer stem cells (CSCs) and upregulation of oncogenes such as c-Myc and cell cycle progression marker, cyclin D1. Taken together, our results support that PD2 is overexpressed in the ducts of PDAC tissues, and results in tumorigenesis and metastasis via upregulation of oncogenes such as c-Myc and cyclin hence D1 implicating PD2 upregulation in pancreatic oncogenesis with targeted therapeutic potential.

Changes in microRNA (miRNA) expression during pancreatic cancer development and progression in a genetically engineered KrasG12D;Pdx1-Cre mouse (KC) model.

Differential expression of microRNAs (miRNAs) has been demonstrated in various cancers, including pancreatic cancer (PC). Due to the lack of tissue samples from early-stages of PC, the stage-specific alteration of miRNAs during PC initiation and progression is largely unknown. In this study, we investigated the global miRNA expression profile and their processing machinery during PC progression using the KrasG12D;Pdx1-Cre (KC) mouse model. At 25 weeks, the miRNA microarray analysis revealed significant downregulation of miR-150, miR-494, miR-138, miR-148a, miR-216a, and miR-217 and upregulation of miR-146b, miR-205, miR-31, miR-192, and miR-21 in KC mice compared to controls. Further, expression of miRNA biosynthetic machinery including Dicer, Exportin-5, TRKRA, and TARBP2 were downregulated, while DGCR8 and Ago2 were upregulated in KC mice. In addition, from 10 to 50 weeks of age, stage-specific expression profiling of miRNA in KC mice revealed downregulation of miR-216, miR-217, miR-100, miR-345, miR-141, miR-483-3p, miR-26b, miR-150, miR-195, Let-7b and Let-96 and upregulation of miR-21, miR-205, miR-146b, miR-34c, miR-1273, miR-223 and miR-195 compared to control mice. Interestingly, the differential expression of miRNA in mice also corroborated with the miRNA expression in human PC cell lines and tissue samples; ectopic expression of Let-7b in CD18/HPAF and Capan1 cells resulted in the downregulation of KRAS and MSST1 expression. Overall, the present study aids an understanding of miRNA expression patterns during PC pathogenesis and helps to facilitate the identification of promising and novel early diagnostic/prognostic markers and therapeutic targets.

PD2/Paf1 depletion in pancreatic acinar cells promotes acinar-to-ductal metaplasia.

Pancreatic differentiation 2 (PD2), a PAF (RNA Polymerase II Associated Factor) complex subunit, is overexpressed in pancreatic cancer cells and has demonstrated potential oncogenic property. Here, we report that PD2/Paf1 expression was restricted to acinar cells in the normal murine pancreas, but its expression increased in the ductal cells of KrasG12D/Pdx1Cre (KC) mouse model of pancreatic cancer with increasing age, showing highest expression in neoplastic ductal cells of 50 weeks old mice. PD2/Paf1 was specifically expressed in amylase and CK19 double positive metaplastic ducts, representing intermediate structures during pancreatic acinar-to-ductal metaplasia (ADM). Similar PD2/Paf1 expression was observed in murine pancreas that exhibited ADM-like histology upon cerulein challenge. In normal mice, cerulein-mediated inflammation induced a decrease in PD2/Paf1 expression, which was later restored upon recovery of the pancreatic parenchyma. In KC mice, however, PD2/Paf1 mRNA level continued to decrease with progressive dysplasia and subsequent neoplastic transformation. Additionally, knockdown of PD2/Paf1 in pancreatic acinar cells resulted in the abrogation of Amylase, Elastase and Lipase (acinar marker) mRNA levels with simultaneous increase in CK19 and CAII (ductal marker) transcripts. In conclusion, our studies indicate loss of PD2/Paf1 expression during acinar transdifferentiation in pancreatic cancer initiation and PD2/Paf1 mediated regulation of lineage specific markers.

Immunocytochemistry for MUC4 and MUC16 is a useful adjunct in the diagnosis of pancreatic adenocarcinoma on fine-needle aspiration cytology.

CONTEXT: Diagnoses rendered as atypical/suspicious for malignancy on fine-needle aspiration (FNA) of pancreatic mass lesions range from 2% to 29% in various studies. We have identified the expression of 3 genes, MUC4, MUC16, and NGAL that are highly upregulated in pancreatic adenocarcinoma. In this study, we analyzed the expression of these markers in FNA samples to determine whether they could improve sensitivity and specificity. OBJECTIVE: To evaluate the utility of MUC4, MUC16, and NGAL in the evaluation of pancreatic FNA specimens. DESIGN: Records of pancreatic FNAs performed during 10 consecutive years were reviewed. Unstained sections from corresponding cell blocks were immunostained for MUC4, MUC16, and NGAL (polyclonal). Immunostaining was assessed using the H-score (range, 0-3). Any case with an H-score of >0.5 was considered positive. RESULTS: Cases were classified using cytomorphologic criteria as adenocarcinoma (31 of 64; 48.4%), benign (17 of 64; 26.6%), and atypical/suspicious (16 of 64; 25%). On follow-up, all cases (100%; 31 of 31) diagnosed as carcinoma on cytology were confirmed on biopsy/resection samples or by clinical follow-up (such as unresectable disease). Of the cases diagnosed as atypical/suspicious, 69% (11 of 16) were found to be positive for adenocarcinoma and 31% (5 of 16) were benign on subsequent follow-up. Overall sensitivity and specificity, respectively, for the various markers for the detection of pancreatic adenocarcinoma were as follows: MUC4 (74% and 100%), MUC16 (62.9% and 100%), and NGAL (61.3% and 58.8%). In cases that were atypical/suspicious on cytology, expression of MUC4 and MUC16 was 100% specific for carcinoma with sensitivities of 63.6% and 66.7%, respectively. CONCLUSION: Immunocytochemistry for MUC4 and MUC16 appears to be a useful adjunct in the classification of pancreatic FNA samples, especially in cases that are equivocal (atypical/suspicious) for adenocarcinoma on cytomorphologic assessment.

Mucin (Muc) expression during pancreatic cancer progression in spontaneous mouse model: potential implications for diagnosis and therapy.

BACKGROUND: Pancreatic cancer (PC) is a lethal malignancy primarily driven by activated Kras mutations and characterized by the deregulation of several genes including mucins. Previous studies on mucins have identified their significant role in both benign and malignant human diseases including PC progression and metastasis. However, the initiation of MUC expression during PC remains unknown because of lack of early stage tumor tissues from PC patients. METHODS: In the present study, we have evaluated stage specific expression patterns of mucins during mouse PC progression in (Kras(G12D);Pdx1-Cre (KC)) murine PC model from pancreatic intraepithelial neoplasia (PanIN) to pancreatic ductal adenocarcinoma (PDAC) by immunohistochemistry and quantitative real-time PCR. RESULTS: In agreement with previous studies on human PC, we observed a progressive increase in the expression of mucins particularly Muc1, Muc4 and Muc5AC in the pancreas of KC (as early as PanIN I) mice with advancement of PanIN lesions and PDAC both at mRNA and protein levels. Additionally, mucin expression correlated with the increased expression of inflammatory cytokines IFN-γ (p < 0.0062), CXCL1 (p < 0.00014) and CXCL2 (p < 0.08) in the pancreas of KC mice, which are known to induce mucin expression. Further, we also observed progressive increase in inflammation in pancreas of KC mice from 10 to 50 weeks of age as indicated by the increase in the macrophage infiltration. Overall, this study corroborates with previous human studies that indicated the aberrant overexpression of MUC1, MUC4 and MUC5AC mucins during the progression of PC. CONCLUSIONS: Our study reinforces the potential utility of the KC murine model for determining the functional role of mucins in PC pathogenesis by crossing KC mice with corresponding mucin knockout mice and evaluating mucin based diagnostic and therapeutic approaches for lethal PC.

Overexpression of ecdysoneless in pancreatic cancer and its role in oncogenesis by regulating glycolysis.

PURPOSE: To study the expression and function of a novel cell-cycle regulatory protein, human ecdysoneless (Ecd), during pancreatic cancer pathogenesis. EXPERIMENTAL DESIGN: Immunohistochemical expression profiling of Ecd was done in nonneoplastic normal pancreatic tissues and pancreatic ductal adenocarcinoma lesions (from tissue microarray and Rapid Autopsy program) as well as precancerous PanIN lesions and metastatic organs. To analyze the biological significance of Ecd in pancreatic cancer progression, Ecd was stably knocked down in pancreatic cancer cell line followed by in vitro and in vivo functional assays. RESULTS: Normal pancreatic ducts showed very weak to no Ecd expression compared to significant positive expression in pancreatic cancer tissues (mean ± SE composite score: 0.3 ± 0.2 and 3.8 ± 0.2 respectively, P < 0.0001) as well as in PanIN precursor lesions with a progressive increase in Ecd expression with increasing dysplasia (PanIN-1-PanIN-3). Analysis of matched primary tumors and metastases from patients with pancreatic cancer revealed that Ecd is highly expressed in both primary pancreatic tumor and in distant metastatic sites. Furthermore, knockdown of Ecd suppressed cell proliferation in vitro and tumorigenicity of pancreatic cancer cells in mice orthotopic tumors. Microarray study revealed that Ecd regulates expression of glucose transporter GLUT4 in pancreatic cancer cells and was subsequently shown to modulate glucose uptake, lactate production, and ATP generation by pancreatic cancer cells. Finally, knockdown of Ecd also reduced level of pAkt, key signaling molecule known to regulate aerobic glycolysis in cancer cells. CONCLUSION: Ecd is a novel tumor-promoting factor that is differentially expressed in pancreatic cancer and potentially regulates glucose metabolism within cancer cells.

Human RNA polymerase II-association factor 1 (hPaf1/PD2) regulates histone methylation and chromatin remodeling in pancreatic cancer.

Change in gene expression associated with pancreatic cancer could be attributed to the variation in histone posttranslational modifications leading to subsequent remodeling of the chromatin template during transcription. However, the interconnected network of molecules involved in regulating such processes remains elusive. hPaf1/PD2, a subunit of the human PAF-complex, involved in the regulation of transcriptional elongation has oncogenic potential. Our study explores the possibility that regulation of histone methylation by hPaf1 can contribute towards alteration in gene expression by nucleosomal rearrangement. Here, we show that knockdown of hPaf1/PD2 leads to decreased di- and tri-methylation at histone H3 lysine 4 residues in pancreatic cancer cells. Interestingly, hPaf1/PD2 colocalizes with MLL1 (Mixed Lineage Leukemia 1), a histone methyltransferase that methylates H3K4 residues. Also, a reduction in hPaf1 level resulted in reduced MLL1 expression and a corresponding decrease in the level of CHD1 (Chromohelicase DNA-binding protein 1), an ATPase dependent chromatin remodeling enzyme that specifically binds to H3K4 di and trimethyl marks. hPaf1/PD2 was also found to interact and colocalize with CHD1 in both cytoplasmic and nuclear extracts of pancreatic cancer cells. Further, reduced level of CHD1 localization in the nucleus in hPaf1/PD2 Knockdown cells could be rescued by ectopic expression of hPaf1/PD2. Micrococcal nuclease digestion showed an altered chromatin structure in hPaf1/PD2-KD cells. Overall, our results suggest that hPaf1/PD2 in association with MLL1 regulates methylation of H3K4 residues, as well as interacts and regulates nuclear shuttling of chromatin remodeling protein CHD1, facilitating its function in pancreatic cancer cells.

MUC4 stabilizes HER2 expression and maintains the cancer stem cell population in ovarian cancer cells.

BACKGROUND: Recent evidence has suggested that the capability of cancer to grow, propagate and relapse after therapy is dependent on a small subset of the cell population within the tumor, called cancer stem cells. Therefore, this subpopulation of cells needs to be targeted with different approaches by identification of unique stem-cell specific target antigens. One of the well known tumor antigens is the epithelial cell mucin MUC4, which is aberrantly expressed in ovarian cancer as compared to the normal ovary and plays a pivotal role in the aggressiveness and metastasis of ovarian cancer cells. In the present study, we aimed to analyze the cancer stem cell population in MUC4 overexpressed ovarian cancer cells. METHODS: MUC4 was ectopically overexpressed in SKOV3 ovarian cancer cells. Western blot analysis was performed for MUC4, HER2, CD133, ALDH1 and Shh expression in MUC4 overexpressed cells. Confocal analysis of MUC4, HER2 and CD133 was also done in the MUC4 overexpressed cells. CD133 and Hoechst33342 dye staining was used to analyze the cancer stem cell population via FACS method in SKOV3-MUC4 cells. RESULTS: MUC4 overexpressed SKOV3 cells showed an increased expression of HER2 compared to control cells. MUC4 overexpression leads to increased (0.1%) side population (SP) and CD133-positive cancer stem cells compared to the control cells. Interestingly, the tumor sphere type circular colony formation was observed only in the MUC4 overexpressed ovarian cancer cells. Furthermore, the cancer stem cell marker CD133 was expressed along with MUC4 in the isolated circular colonies as analyzed by both confocal and western blot analysis. HER2 and cancer stem cell specific marker ALDH1 along with Shh, a self-renewal marker, showed increased expression in the isolated circular colonies compared to MUC4-transfected cells. CONCLUSION: These studies demonstrate that MUC4 overexpression leads to an enriched ovarian cancer stem cell population either directly or indirectly through HER2. In future, this study would be helpful for MUC4-directed therapy for the ovarian cancer stem cell population.

RNA polymerase II associated factor 1/PD2 maintains self-renewal by its interaction with Oct3/4 in mouse embryonic stem cells.

Embryonic stem cells (ESCs) maintain self-renewal while ensuring a rapid response to differentiation signals, but the exact mechanism of this process remains unknown. PD2 is the human homolog of the RNA polymerase II-associated factor 1 (Paf1). The Paf1/PD2 is a member of the human PAF complex that consists of four other subunits, hCdc73, hLeo1, hCtr9, and hSki8, and is involved in the regulation of transcriptional elongation and further downstream events. Here, we show that Paf1/PD2 is overexpressed in mouse ESCs and is involved in the maintenance of mouse ESCs. The Paf1/PD2 knockdown and knockout ESCs grown under self-renewal conditions express substantially reduced levels of self-renewal regulators, including Oct3/4, SOX2, Nanog, and Shh. We observed that the level of Paf1/PD2 expression is much higher in self-renewing mouse embryonic carcinoma cells than in the differentiating cells. Knockout of Paf1/PD2 altered ESC phenotype by increasing apoptosis and decreasing the percentage of cells in S-phase of the cell cycle. Interestingly, we found that the key genes that regulate endodermal differentiation (Gata4, Gata6, and Fgf8) are induced in the Paf1/PD2 heterozygous knockout ESCs. This suggests that Paf1/PD2 plays a specific role in regulating early commitment of ESCs to endodermal differentiation. Furthermore, for the first time, we showed that Paf1/PD2 protein interacts with Oct3/4 and RNA polymerase II, and through this interaction Paf1/PD2 may regulate Oct3/4-mediated gene expression. Thus, the Paf1/PD2 protein is a newly discovered element of the interconnected regulatory network that maintains the self-renewal of mouse ESCs.

Human PAF complexes in endocrine tumors and pancreatic cancer.

The human RNA polymerase II-associated factor (hPAF) complex is comprised of five subunits that include hPaf1, parafibromin, hLeo1, hCtr9 and hSki8. This multifaceted complex was first identified in yeast (yPAF) and subsequently in Drosophila and humans. Recent advances in the study on hPAF have revealed various functions of the complex in humans that are similar to yPAF, including efficient transcription elongation, mRNA quality control and cell cycle regulation. A major component of the hPAF complex, hPaf1, is amplified and overexpressed in pancreatic cancer. The parafibromin subunit of the hPAF complex is a product of the hereditary hyperparathyroidism type 2 (HRPT-2) tumor-suppressor gene, which is mutated in the germ line of hyperparathyroidism-jaw tumor patients. This review evaluates the role of the hPAF complex and its individual subunits in endocrine and pancreatic cancers. It focuses on the functions of the hPAF complex and its individual subunits and dysregulation of the complex, thus providing an insight into its potential involvement in the development of endocrine cancers and other tumor types.