PIM1 targeted degradation prevents the emergence of chemoresistance in prostate cancer.

PIM kinases have important pro-tumorigenic roles and mediate several oncogenic traits, including cell proliferation, survival, and chemotherapeutic resistance. As a result, multiple PIM inhibitors have been pursued as investigational new drugs in cancer; however, response to PIM inhibitors in solid tumors has fallen short of expectations. We found that inhibition of PIM kinase activity stabilizes protein levels of all three PIM isoforms (PIM1/2/3), and this can promote resistance to PIM inhibitors and chemotherapy. To overcome this effect, we designed PIM proteolysis targeting chimeras (PROTACs) to target PIM for degradation. PIM PROTACs effectively downmodulated PIM levels through the ubiquitin-proteasome pathway. Importantly, degradation of PIM kinases was more potent than inhibition of catalytic activity at inducing apoptosis in prostate cancer cell line models. In conclusion, we provide evidence of the advantages of degrading PIM kinases versus inhibiting their catalytic activity to target the oncogenic functions of PIM kinases.

PIM1 drives lipid droplet accumulation to promote proliferation and survival in prostate cancer.

Lipid droplets (LDs) are dynamic organelles with a neutral lipid core surrounded by a phospholipid monolayer. Solid tumors exhibit LD accumulation, and it is believed that LDs promote cell survival by providing an energy source during energy deprivation. However, the precise mechanisms controlling LD accumulation and utilization in prostate cancer are not well known. Here, we show peroxisome proliferator-activated receptor α (PPARα) acts downstream of PIM1 kinase to accelerate LD accumulation and promote cell proliferation in prostate cancer. Mechanistically, PIM1 inactivates glycogen synthase kinase 3 beta (GSK3ß) via serine 9 phosphorylation. GSK3ß inhibition stabilizes PPARα and enhances the transcription of genes linked to peroxisomal biogenesis (PEX3 and PEX5) and LD growth (Tip47). The effects of PIM1 on LD accumulation are abrogated with GW6471, a specific inhibitor for PPARα. Notably, LD accumulation downstream of PIM1 provides a significant survival advantage for prostate cancer cells during nutrient stress, such as glucose depletion. Inhibiting PIM reduces LD accumulation in vivo alongside slow tumor growth and proliferation. Furthermore, TKO mice, lacking PIM isoforms, exhibit suppression in circulating triglycerides. Overall, our findings establish PIM1 as an important regulator of LD accumulation through GSK3ß-PPARα signaling axis to promote cell proliferation and survival during nutrient stress.

PIM1 phosphorylates ABI2 to enhance actin dynamics and promote tumor invasion.

Distinguishing key factors that drive the switch from indolent to invasive disease will make a significant impact on guiding the treatment of prostate cancer (PCa) patients. Here, we identify a novel signaling pathway linking hypoxia and PIM1 kinase to the actin cytoskeleton and cell motility. An unbiased proteomic screen identified Abl-interactor 2 (ABI2), an integral member of the wave regulatory complex (WRC), as a PIM1 substrate. Phosphorylation of ABI2 at Ser183 by PIM1 increased ABI2 protein levels and enhanced WRC formation, resulting in increased protrusive activity and cell motility. Cell protrusion induced by hypoxia and/or PIM1 was dependent on ABI2. In vivo smooth muscle invasion assays showed that overexpression of PIM1 significantly increased the depth of tumor cell invasion, and treatment with PIM inhibitors significantly reduced intramuscular PCa invasion. This research uncovers a HIF-1-independent signaling axis that is critical for hypoxia-induced invasion and establishes a novel role for PIM1 as a key regulator of the actin cytoskeleton.

MASTL regulates EGFR signaling to impact pancreatic cancer progression.

Pancreatic cancer (PC) remains a major cause of cancer-related deaths primarily due to its inherent potential of therapy resistance. Checkpoint inhibitors have emerged as promising anti-cancer agents when used in combination with conventional anti-cancer therapies. Recent studies have highlighted a critical role of the Greatwall kinase (microtubule-associated serine/threonine-protein kinase-like (MASTL)) in promoting oncogenic malignancy and resistance to anti-cancer therapies; however, its role in PC remains unknown. Based on a comprehensive investigation involving PC patient samples, murine models of PC progression (Kras;PdxCre-KC and Kras;p53;PdxCre-KPC), and loss and gain of function studies, we report a previously undescribed critical role of MASTL in promoting cancer malignancy and therapy resistance. Mechanistically, MASTL promotes PC by modulating the epidermal growth factor receptor protein stability and, thereupon, kinase signaling. We further demonstrate that combinatorial therapy targeting MASTL promotes the efficacy of the cell-killing effects of Gemcitabine using both genetic and pharmacological inhibitions. Taken together, this study identifies a key role of MASTL in promoting PC progression and its utility as a novel target in promoting sensitivity to the anti-PC therapies.

Direct phosphorylation and stabilization of HIF-1α by PIM1 kinase drives angiogenesis in solid tumors.

Angiogenesis is essential for the sustained growth of solid tumors. Hypoxia-inducible factor 1 (HIF-1) is a master regulator of angiogenesis and constitutive activation of HIF-1 is frequently observed in human cancers. Therefore, understanding the mechanisms governing the activation of HIF-1 is critical for successful therapeutic targeting of tumor angiogenesis. Herein, we establish a new regulatory mechanism responsible for the constitutive activation of HIF-1α in cancer, irrespective of oxygen tension. PIM1 kinase directly phosphorylates HIF-1α at threonine 455, a previously uncharacterized site within its oxygen-dependent degradation domain. This phosphorylation event disrupts the ability of prolyl hydroxylases to bind and hydroxylate HIF-1α, interrupting its canonical degradation pathway and promoting constitutive transcription of HIF-1 target genes. Moreover, phosphorylation of the analogous site in HIF-2α (S435) stabilizes the protein through the same mechanism, indicating post-translational modification within the oxygen-dependent degradation domain as a mechanism of regulating the HIF-α subunits. In vitro and in vivo models demonstrate that expression of PIM1 is sufficient to stabilize HIF-1α and HIF-2α in normoxia and stimulate angiogenesis in a HIF-1-dependent manner. CRISPR mutants of HIF-1α (Thr455D) promoted increased tumor growth, proliferation, and angiogenesis. Moreover, HIF-1α-T455D xenograft tumors were refractory to the anti-angiogenic and cytotoxic effects of PIM inhibitors. These data identify a new signaling axis responsible for hypoxia-independent activation of HIF-1 and expand our understanding of the tumorigenic role of PIM1 in solid tumors.

Targeting dual signalling pathways in concert with immune checkpoints for the treatment of pancreatic cancer.

OBJECTIVE: This study exploits the intersection between molecular-targeted therapies and immune-checkpoint inhibition to define new means to treat pancreatic cancer. DESIGN: Patient-derived cell lines and xenograft models were used to define the response to CDK4/6 and MEK inhibition in the tumour compartment. Impacts relative to immunotherapy were performed using subcutaneous and orthotopic syngeneic models. Single-cell RNA sequencing and multispectral imaging were employed to delineate effects on the immunological milieu in the tumour microenvironment. RESULTS: We found that combination treatment with MEK and CDK4/6 inhibitors was effective across a broad range of PDX models in delaying tumour progression. These effects were associated with stable cell-cycle arrest, as well as the induction of multiple genes associated with interferon response and antigen presentation in an RB-dependent fashion. Using single-cell sequencing and complementary approaches, we found that the combination of CDK4/6 and MEK inhibition had a significant impact on increasing T-cell infiltration and altering myeloid populations, while potently cooperating with immune checkpoint inhibitors. CONCLUSIONS: Together, these data indicate that there are canonical and non-canonical features of CDK4/6 and MEK inhibition that impact on the tumour and immune microenvironment. This combination-targeted treatment can promote robust tumour control in combination with immune checkpoint inhibitor therapy.

Synergistic antitumor effect of 5-fluorouracil and withaferin-A induces endoplasmic reticulum stress-mediated autophagy and apoptosis in colorectal cancer cells.

The development of chemo-resistance against 5-fluorouracil (5-FU) in tumor cells is one of the main debacles in colorectal cancer (CRC) patients. A recent combination of 5-FU with oxaliplatin or cetuximab drastically improves the survival rate in CRC patients; however, the toxicity issue cannot be evaded completely. Thus, searching for novel drug combinations with high specificity and low toxicity is seemingly important. Owing to the less undesirable effects of natural products on normal cells, here we investigated the synergistic antitumor effect of withaferin-A (WA) in combination with 5-FU. Our results demonstrate that the combination of WA and 5-FU induces a significant antiproliferative effect and modulates endoplasmic reticulum (ER) stress in favor of cell death in colorectal cancer (CRC) cells. Mechanistically, the combination upregulates the expression of ER stress sensors (BiP, PERK, CHOP, ATF-4, and eIF2α) and executes PERK axis mediated apoptosis in CRC cells. Additionally, the combined treatment of WA and 5-FU mediated ER stress induces autophagy and apoptosis, which were confirmed by immunoblotting, acridine orange (AO) staining and annexin-V FITC by flow cytometry. In contrast, inhibition of ER stress with salubrinal significantly decreases both autophagic and apoptotic cell populations. Moreover, pharmacological inhibition of either autophagy or apoptosis by their respective inhibitors 3-methyladenine (3-MA) or carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoro-methyl ketone (Z-VAD-FMK) decreases their respective population of cells but could not affect either of the population significantly. Finally, the combination attenuates the expression of ß-catenin pathway associated proteins and arrests cell cycle at the G2M phase in CRC cells. In summary, the combination of WA and 5-FU decreases cell viability by inducing ER stress-mediated induction of autophagy and apoptosis, inhibiting the ß-catenin pathway and arresting the cell cycle at a G2M phase in CRC cells.

PIM kinases alter mitochondrial dynamics and chemosensitivity in lung cancer.

Resistance to chemotherapy represents a major obstacle to the successful treatment of non-small-cell lung cancer (NSCLC). The goal of this study was to determine how PIM kinases impact mitochondrial dynamics, ROS production, and response to chemotherapy in lung cancer. Live-cell imaging and microscopy were used to determine the effect of PIM loss or inhibition on mitochondrial phenotype and ROS. Inhibition of PIM kinases caused excessive mitochondrial fission and significant upregulation of mitochondrial superoxide, increasing intracellular ROS. Mechanistically, we define a signaling axis linking PIM1 to Drp1 and mitochondrial fission in lung cancer. PIM inhibition significantly increased the protein levels and mitochondrial localization of Drp1, causing marked fragmentation of mitochondria. An inverse correlation between PIM1 and Drp1 was confirmed in NSCLC patient samples. Inhibition of PIM sensitized NSCLC cells to chemotherapy and produced a synergistic antitumor response in vitro and in vivo. Immunohistochemistry and transmission electron microscopy verified that PIM inhibitors promote mitochondrial fission and apoptosis in vivo. These data improve our knowledge about how PIM1 regulates mitochondria and provide justification for combining PIM inhibition with chemotherapy in NSCLC.

Cell cycle plasticity driven by MTOR signaling: integral resistance to CDK4/6 inhibition in patient-derived models of pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC), like many KRAS-driven tumors, preferentially loses CDKN2A that encodes an endogenous CDK4/6 inhibitor to bypass the RB-mediated cell cycle suppression. Analysis of a panel of patient-derived cell lines and matched xenografts indicated that many pancreatic cancers have intrinsic resistance to CDK4/6 inhibition that is not due to any established mechanism or published biomarker. Rather, there is a KRAS-dependent rapid adaptive response that leads to the upregulation of cyclin proteins, which participate in functional complexes to mediate resistance. In vivo, the degree of response is associated with the suppression of a gene expression signature that is strongly prognostic in pancreatic cancer. Resistance is associated with an adaptive gene expression signature that is common to multiple kinase inhibitors, but is attenuated with MTOR inhibitors. Combination treatment with MTOR and CDK4/6 inhibitors had potent activity across a large number of patient-derived models of PDAC underscoring the potential clinical efficacy.

Dual Inhibition of Bruton's Tyrosine Kinase and Phosphoinositide-3-Kinase p110δ as a Therapeutic Approach to Treat Non-Hodgkin's B Cell Malignancies.

Although new targeted therapies, such as ibrutinib and idelalisib, have made a large impact on non-Hodgkin's lymphoma (NHL) patients, the disease is often fatal because patients are initially resistant to these targeted therapies, or because they eventually develop resistance. New drugs and treatments are necessary for these patients. One attractive approach is to inhibit multiple parallel pathways that drive the growth of these hematologic tumors, possibly prolonging the duration of the response and reducing resistance. Early clinical trials have tested this approach by dosing two drugs in combination in NHL patients. We discovered a single molecule, MDVN1003 (1-(5-amino-2,3-dihydro-1H-inden-2-yl)-3-(8-fluoro-3,4-dihydro-2H-benzo[b][1,4]oxazin-6-yl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine), that inhibits Bruton's tyrosine kinase and phosphatidylinositol-3-kinase δ, two proteins regulated by the B cell receptor that drive the growth of many NHLs. In this report, we show that this dual inhibitor prevents the activation of B cells and inhibits the phosphorylation of protein kinase B and extracellular signal-regulated kinase 1/2, two downstream mediators that are important for this process. Additionally, MDVN1003 induces cell death in a B cell lymphoma cell line but not in an irrelevant erythroblast cell line. Importantly, we found that this orally bioavailable dual inhibitor reduced tumor growth in a B cell lymphoma xenograft model more effectively than either ibrutinib or idelalisib. Taken together, these results suggest that dual inhibition of these two key pathways by a single molecule could be a viable approach for treatment of NHL patients.

Ethanol and age enhances fluoride toxicity through oxidative stress and mitochondrial dysfunctions in rat intestine.

Fluoride toxicity and alcohol abuse are the two serious public health problems in many parts of the world. The current study was an attempt to investigate the effect of alcohol administration and age on fluoride toxicity in rat intestine. Six and 18 months old female Sprague Dawley rats were exposed to sodium fluoride (NaF, 25 mg/kg), 30 % ethanol (EtOH, 1 ml/kg), and NaF+EtOH (25 mg/kg+1 ml/kg) for a period of 20, 40, and 90 days. The levels of lipid peroxidation were increased, while the content of reduced glutathione, total, and protein thiol was decreased with NaF treatment. Under these conditions, animals showed an age-related decline in the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase which were further aggravated upon NaF or/and EtOH treatment. Mitochondrial respiration rate and the activities of complexes I, II, and IV enzymes of electron transport chain were decreased, while the levels of nitric oxide and citrulline were increased with age and NaF or/and EtOH treatment. Histological examination revealed large reactive lymphoid follicles, excess of lymphocytes in lamina propria of villi, villous edema, focal ileitis, necrosis of villi, and ulceration in NaF- or/and EtOH-treated animals in both the age groups. These findings suggest that fluoride mediate its toxic effects on intestine through oxidative stress and mitochondrial dysfunctions which are further augmented with alcohol consumption and advancing age.

Growth inhibition and apoptosis induction by (+)-Cyanidan-3-ol in hepatocellular carcinoma.

The objective of this study was to evaluate the cytotoxicity of (+)-cyanidan-3-ol (CD-3) in human hepatocellular carcinoma cell line (HepG2) and chemopreventive potential against hepatocellular carcinoma (HCC) in Balb/c mice. The HepG2 cell line was treated with CD-3 at various concentrations and the proliferation of the HepG2 cells was measure by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT), sulforhodamine B (SRB) and lactate dehydrogenase (LDH) assays. Cell apoptosis was detected by Hoechst 33258 (HO), Acridine orange/ethylene dibromide (AO/EB) staining, DNA fragmentation analysis and the apoptosis rate was detected by flow cytometry. The HCC tumor model was established in mice by injecting N-nitrosodiethylamine/carbon tetrachloride (NDEA/CCl4) and the effect of CD-3 on tumor growth in-vivo was studied. The levels of liver injury markers, tumor markers, and oxidative stress were measured. The expression levels of apoptosis-related genes in in-vitro and in vivo models were determined by RT-PCR and ELISA. The CD-3 induced cell death was considered to be apoptotic by observing the typical apoptotic morphological changes under fluorescent microscopy and DNA fragmentation analysis. Annexin V/PI assay demonstrated that apoptosis increased with increase in the concentration of CD-3. The expression levels of apoptosis-related genes that belong to bcl-2 and caspase family were increased and AP-1 and NF-κB activities were significantly suppressed by CD-3. Immunohistochemistry data revealed less localization of p53, p65 and c-jun in CD-3 treated tumors as compared to localization in NDEA/CCl4 treated tumors. Taken together, our data demonstrated that CD-3 could significantly inhibit the proliferation of HepG2 cells in-vitro and suppress HCC tumor growth in-vivo by apoptosis induction.

Effects of fluoride and ethanol administration on lipid peroxidation systems in rat brain.

Exposure to fluoride and excessive ethanol consumption has been identified as a serious public health problem in many parts of the world, including India. Thus, the effect of co-exposure to fluoride and ethanol for 3-6 weeks was studied on lipid peroxidation (LPO) and oxidative stress related parameters in the rat brain. After 3 weeks, co-treated animals showed 95% increase in LPO levels compared to control. However, the levels of reduced glutathione, total and protein thiols were decreased. These changes were accompanied by a decrease in the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase. Rats exposed to fluoride together with ethanol for 6 weeks resulted in 130% increase in LPO and decrease in the reduced glutathione levels. The activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase were reduced under these conditions. Brain histology revealed excessive lymphocytes, edema and spongeosis in the cortical region after six weeks of fluoride and ethanol treatment. These results suggest that exposure to fluoride together with ethanol enhances lipid peroxidation by affecting antioxidant defence systems in the rat brain.

Modulation of intestinal brush border membrane chemical composition during postnatal development in rats: effect of gestational diabetes.

There was a significant increase in fucose (52%), total hexoses (16%) and hexosamine (56%) except sialic acid, which was reduced (77%) in the microvillus membrane of infants born to rat mothers made diabetic by injecting alloxan on day 3 of gestation. Expressed on the protein basis there were a significant increase in membrane, triglyceride, total cholesterol, and phospholipids content of brush border in pups from diabetic group between 5-45 days of postnatal age. Intestinal morphology in diabetic group showed, regression of tubular glands, distorted cellular organization of mucosal cells, reduction in the mucosal cell height and number of secretory goblet cells. These findings suggest that the gestational diabetes affects the sugar and lipid composition of the intestinal brush border membrane in rats during early stages of the postnatal development, which may be associated with compromised tissue functions later in life.

Gestational diabetes affects postnatal development of transport and enzyme functions in rat intestine.

The effect of alloxan-induced gestational diabetes on the postnatal development of brush border disaccharidases and D-glucose transport in rat intestine was studied. Pups born to diabetic mothers showed 92-22% increase in blood sugar levels compared with the controls. Western blot and RT-PCR analyses revealed that the activities of brush border sucrase, lactase and Sodium Glucose Co-transporter 1 (SGLT1) correlates with protein and mRNA levels in intestine of pups born to diabetic rat mothers after 5-45 days of birth. Intestinal histology in pups born to diabetic mothers at day 10 and 45 after birth showed distorted cellular organization of mucosa with a decrease in the number of secretary goblet cells and regression of tubular mass. These findings suggest that the genetic switch in utero regulates the postnatal expression of enzyme and transport functions in intestine of pups born to diabetic rat mothers. This may influence the growth and development of offsprings later in life.

Modulation of lipid peroxidation and antioxidant defense systems in rat intestine by subchronic fluoride and ethanol administration.

Excessive consumption of fluoride and ethanol has been identified as injurious to human health. Fluoride and ethanol co-exposures are commonly seen among the alcoholics residing in endemic fluoride areas worldwide. This study was undertaken to examine the modulation of lipid peroxidation and antioxidant defense systems in rat intestine by subchronic fluoride and ethanol administration. Female Sprague-Dawley rats were divided into four groups: group I (control), group II (fluoride was given orally at a dose of 25 mg/kg body weight), group III (30% ethanol was given orally at a dose of 1 mL/kg body weight), and group IV (a combination of fluoride and ethanol was administered orally at the dose described for groups II and III). Lipid peroxidation was elevated (P<.05) in intestine of rats by fluoride or ethanol treatments for 20 or 40 days. However, glutathione content was reduced by fluoride (32 and 44%) and ethanol (21 and 40%) treatments after 20 and 40 days, respectively. Fluoride-exposed animals showed reduction (P<.05) in the activities of superoxide dismutase (22 and 42%), catalase (30 and 37%), glutathione peroxidase (22 and 35%), glutathione reductase (32 and 34%), and glutathione-S-transferase (24 and 30%) after 20 and 40 days. A similar decrease (P<.05) in the activities of these enzymes was also noticed in animals exposed to ethanol for 20 or 40 days. The observed changes in lipid peroxidation, reduced glutathione levels, and enzyme systems were further augmented in intestine of rats exposed to fluoride and ethanol together. Intestinal histology showed large reactive lymphoid follicles along with mild excess of lymphocytes in lamina propria of villi, villous edema, focal ileitis, and necrosis of villi in animals exposed to fluoride and ethanol for 40 days. These findings suggest that fluoride and ethanol exposure induces considerable changes in lipid peroxidation, antioxidant defense, and morphology of rat intestine, which may affect its functions.