Priyatham Gorjala

Androgen receptor signaling is crucial for prostate cancer growth and is positively regulated in part by intratumoral CYP3A5. As African American (AA) men often carry the wild type CYP3A5 and express high levels of CYP3A5 protein, we blocked the wild type CYP3A5 in AA origin prostate cancer cells and tested its effect on androgen receptor signaling. q-PCR based profiler assay identified several AR regulated genes known to regulate AR nuclear translocation, cell cycle progression, and cell growth. CYP3A5 processes several commonly prescribed drugs and many of these are CYP3A5 inducers or inhibitors. In this study, we test the effect of these commonly prescribed CYP3A5 inducers/inhibitors on AR signaling. The results show that the CYP3A5 inducers promoted AR nuclear translocation, downstream signaling, and cell growth, whereas CYP3A5 inhibitors abrogated them. The observed changes in AR activity is specific to alterations in CYP3A5 activity as the effects are reduced in the CYP3A5 knockout background. Both the inducers tested demonstrated increased cell growth of prostate cancer cells, whereas the inhibitors showed reduced cell growth. Further, characterization and utilization of the observation that CYP3A5 inducers and inhibitors alter AR signaling may provide guidance to physicians prescribing CYP3A5 modulating drugs to treat comorbidities in elderly patients undergoing ADT, particularly AA.

Background: Androgen receptor signaling is crucial for prostate cancer growth and is regulated by intratumoral CYP3A5. As African American (AA) men often carry the wild type CYP3A5 and express high level of CYP3A5 protein, we tested the effect of blocking the wild type CYP3A5 in prostate cancer cells from AA men on androgen receptor signaling. CYP3A5 processes several commonly prescribed drugs and many of these are CYP3A5 inducers (e.g. phenytoin and rifampicin) or inhibitors (e.g. ritonavir and amiodarone). In this study, we test the effect of these commonly prescribed CYP3A5 inducers/inhibitors on AR signaling in prostate cancer cells.Methods: Cell fractionation and immunofluorescence studies were performed to study AR nuclear localization and activation process using CYP3A5 siRNA and CYP3A5 inducers and inhibitors. A qPCR based array was employed to examine expression of AR downstream regulated genes after blocking CYP3A5 expression using a pool of CYP3A5 siRNA. Cell growth was monitored using MTS based assays. Since AAs tend to carry wild type CYP3A5 and non-Hispanic White Americans (NHWA) carry mutated CYP3A5 two cell lines one of AA origin (MDAPCA2b) carrying wt CYP3A5 and the other of NHWA origin (LNCaP) carrying mutant CYP3A5 were used for above experiments.Results: Similar to that observed in LNCaP (mutant CYP3A5) earlier, CYP3A5 siRNA treated MDACPA2b (AA, wild type CYP3A5) cells showed decreased AR nuclear translocation and PSA production. q-PCR based profiler assay identified several AR regulated genes which were downregulated with CYP3A5 siRNA pool treatment performed with cDNA from CYP3A5 siRNA pool and NT treated MDAPCA2b cells. These downregulated genes include SCL45A3, FKBP5, NCAPD3, MYC, MME, ELL2, PIK3R3, HPRT1 and SPDEF with p-value of ≤0.005. These genes are known to regulate AR nuclear translocation, cell cycle progression and cell growth. SCL45A3, FKBP5, MYC, and ELL2 also showed decreased protein levels after CYP3A5 siRNA treatment.Commonly prescribed drugs which are either CYP3A5 inhibitors (amiodarone, ritonavir) or inducers (phenytoin, rifampicin) were tested for their ability to alter AR signaling in both LNCaP and MDAPCa2b cells. The results show that the CYP3A5 inducers promoted AR nuclear translocation and downstream signaling whereas CYP3A5 inhibitors abrogated them. The increased nuclear AR observed with phenytoin and rifampicin (CYP3A inducers) treatment is abrogated in CYP3A5 siRNA treated MDAPCa2b cells, confirming that the activation of AR activity is specific to changes in CYP3A5 activity. Both the inducers tested demonstrated increased cell growth of prostate cancer cells, whereas the inhibitors showed reduced cell growth. The difference in growth is more pronounced in MDAPCa2b cells which carries a wild type CYP3A5 as compared to LNCaP with the exception of ritonavir which also downregulates total AR levels.Conclusions: Concomitantly prescribed CYP3A5 modulating drugs may alter downstream AR signaling, cell growth and ADT efficacy in men, more so in AAs expressing wild type CYP3A5. Further, characterization and utilization of this observation how CYP3A5 inducers and inhibitors can alter AR signaling may provide guidance to physicians co-prescribing CYP3A5 modulating drugs to treat comorbidities in elderly patients undergoing ADT, particularly AA.

Neoplastic cells proliferate rapidly and obtain requisite building blocks by reprogramming metabolic pathways that favor growth. Previously, we observed that prostate cancer cells uptake and store lipids in the form of lipid droplets, providing building blocks for membrane synthesis, to facilitate proliferation and growth. Mechanisms of lipid uptake, lipid droplet dynamics and their contribution to cancer growth have yet to be defined. This work is focused on elucidating the prostate cancer-specific modifications in lipid storage pathways so that these modified gene products can be identified and therapeutically targeted. To identify genes that promote lipid droplet formation and storage, the expression profiles of candidate genes were assessed and compared between peripheral blood mononuclear cells and prostate cancer cells. Subsequently, differentially expressed genes were inhibited and growth assays performed to elucidate their role in the growth of the cancer cells. Cell cycle, apoptosis and autophagy assays were performed to ascertain the mechanism of growth inhibition. Our results indicate that DGAT1, ABHD5, ACAT1 and ATGL are overexpressed in prostate cancer cells compared to PBMCs and of these overexpressed genes, DGAT1 and ABHD5 aid in the growth of the prostate cancer cells. Blocking the expression of both DGAT1 and ABHD5 results in inhibition of growth, cell cycle block and cell death. DGAT1 siRNA treatment inhibits lipid droplet formation and leads to autophagy where as ABHD5 siRNA treatment promotes accumulation of lipid droplets and leads to apoptosis. Both the siRNA treatments reduce AMPK phosphorylation, a key regulator of lipid metabolism. While DGAT1 siRNA reduces phosphorylation of ACC, the rate limiting enzyme in de novo fat synthesis and triggers phosphorylation of raptor and ULK-1 inducing autophagy and cell death, ABHD5 siRNA decreases P70S6 phosphorylation, leading to PARP cleavage, apoptosis and cell death. Interestingly, DGAT-1 is involved in the synthesis of triacylglycerol where as ABHD5 is a hydrolase and participates in the fatty acid oxidation process, yet inhibition of both enzymes similarly promotes prostate cancer cell death. Inhibition of either DGAT1 or ABHD5 leads to prostate cancer cell death. Both DGAT1 and ABHD5 can be selectively targeted to block prostate cancer cell growth.

Early studies showed nitric oxide as a pro-inflammatory-cytokine-induced toxin involved in pancreatic β-cell destruction during pathogenesis of type-1 diabetes. However, nitric oxide has both cytotoxic and cytoprotective effects on mammalian cells, depending on concentration and micro-environmental surroundings. Our studies have shown that low/physiological-level nitric oxide selectively activates protein kinase G type Iα isoform, promoting cytoprotective/pro-cell-survival effects in many cell types. In bone marrow–derived stromal/mesenchymal stem cells, protein kinase G type Iα mediates autocrine effects of nitric oxide and atrial natriuretic peptide, promoting DNA-synthesis/proliferation and cell survival. In this study, endothelial nitric oxide synthase/neuronal nitric oxide synthase inhibitor L-NIO (L-N(5)-(1-iminoethyl)ornithine), soluble guanylyl cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3,-a] quinoxalin-1-one), atrial natriuretic peptide–receptor inhibitor A71915 and protein kinase G type Iα kinase activity inhibitor DT-2 all increased apoptosis and decreased insulin secretion in RINm5F pancreatic β-cells, suggesting autocrine regulatory role for endogenous nitric oxide– and atrial natriuretic peptide–induced activation of protein kinase G type Iα. In four pancreatic β-cell lines, Beta-TC-6, RINm5F, INS-1 and 1.1B4, protein kinase G type Iα small-interfering RNA decreased phospho-serine-239-VASP (indicator of endogenous protein kinase G type Iα kinase activity), increased apoptosis and decreased proliferation. In protein kinase G type Iα–knockdown β-cell lines, expressions of phospho-protein kinase B (PKB/AKT) (AKT), phospho-Forkhead box protein O1 (FOXO1) (transcriptional repressor of pancreas duodenum homobox-1) and pancreas duodenum homobox-1 were decreased, suppressing proliferation and survival in pancreatic β-cells. The data suggest autocrine nitric oxide/atrial natriuretic peptide–induced activation of protein kinase G type Iα/p-AKT/p-FOXO1 promotes survival and proliferation in pancreatic β-cells, providing therapeutic implications for development of new therapeutic agents for diabetes.

Objectives: Beryllium salts (here, beryllium sulphate) can produce a cytostatic effect in some cell types. The basis for this effect may include increased expression of proliferation inhibitors, reduced expression of proliferation promoters, or both. This study sought to determine the role of p53, the tumour‐suppressing transcription factor, in mediating beryllium‐induced cytostasis.Materials and methods: Human A172 glioma cells express wild‐type TP53 gene. Activity of p53 was experimentally manipulated using siRNA and related approaches. Key elements of the beryllium‐response were compared in normal and p53‐knockdown A172 cells using RT‐PCR and Western blotting.Results: In A172 cells, 10 μm BeSO₄ caused 300% increase in CDKN1A (cyclin‐dependent kinase inhibitor p21) mRNA and 90% reduction of CCNE2 (cyclin E2) mRNA. The increased p21 mRNA and reduced cyclin E2 mRNA were each dependent on presence of functional p53. For p21, increased mRNA led to commensurately increased protein levels. In contrast, reduction in cyclin E2 mRNA levels did not lead to corresponding reductions in cyclin E2 protein. The proteasomal inhibitor MG‐132 caused p53 protein to increase, but it had no effect on cyclin E2 protein levels. Cycloheximide time course studies indicated that the cyclin E2 protein half‐life was more than 12 hours in these cells.Conclusions: Beryllium elicited p53‐dependent changes in mRNA levels of key determinants of cell proliferation such as p21 and cyclin E2. However, cyclin E2 protein appeared to be aberrantly regulated in this cell type, as its turnover was unexpectedly slow.

Profiling cellular proteome is critical to understanding signal integration during cell fate determination. In this study, the capability of capillary isoelectric focusing (cIEF) immunoassays to detect post-translational modifications (PTM) of protein isoforms is demonstrated. cIEF immunoassays exhibit protein detection sensitivity at up to 5 orders of magnitude higher than traditional methods. This detection ultra-sensitivity permits proteomic profiling of several nanograms of tissue samples. cIEF immunoassays are employed to simultaneously profile three protein kinases during fat cell differentiation: cGMP-dependent protein kinase type I (PKG-I) of the nitric oxide (NO) signaling pathway, protein kinase B (Akt) of the insulin signaling pathway, and extracellular signal-regulated kinase (ERK) of the mitogen-activated protein kinase (MAPK) signaling pathway. Interestingly, a switch in the expression level of PKG- isoforms is observed during fat cell differentiation. While both PKG-Iα and PKG-Iβ isoforms are present in preadipocytes, only PKG-Iβ isoform is expressed in adipocytes. On the other hand, the phosphorylation level increases for Akt while decreases for ERK1 and ERK2 following the maturation of preadipocytes into adipocytes. Taken together, cIEF immunoassay provides a highly sensitive means to study fat cell differentiation proteomics. cIEF immunoassay should be a powerful proteomics tool to study complex protein signal integration in biological systems.

Glycogen synthase kinase 3β (GSK-3β) is a key regulator in signaling networks that control cell proliferation, metabolism, development, and other processes. Lithium chloride is a GSK-3 family inhibitor that has been a mainstay of in vitro and in vivo studies for many years. Beryllium salt has the potential to act as a lithium-like inhibitor of GSK-3, but it is not known whether this agent is effective under physiologically relevant conditions. Here we show that BeSO₄ inhibits endogenous GSK-3β in cultured human cells. Exposure to 10 µM Be²⁺ produced a decrease in GSK-3β kinase activity that was comparable to that produced by 10 mM Li⁺, indicating that beryllium is about 1,000-fold more potent than the classical inhibitor when treating intact cells. There was a statistically significant dose-dependent reduction in specific activity of GSK-3β immunoprecipitated from cells that had been treated with either agent. Lithium inhibited GSK-3β kinase activity directly, and it also caused GSK-3β in cells to become phosphorylated at serine-9 (Ser-9), a post-translational modification that occurs as part of a well-known positive feedback loop that suppresses the kinase activity. Beryllium also inhibited the kinase directly, but unlike lithium it had little effect on Ser-9 phosphorylation in the cell types tested, suggesting that alternative modes of feedback inhibition may be elicited by this agent. These results indicate that beryllium, like lithium, can induce perturbations in the GSK-3β signaling network of treated cells.

In fibroblasts, beryllium salt causes activation of the p53 transcription factor and induction of a senescence-like state. It is not known whether Be2+ can affect the proliferation of cancer cells, which are generally unsusceptible to senescence. A172 glioblastoma and RKO colon carcinoma cell lines each have wildtype p53, so these cell types have the potential to be responsive to agents that activate p53. In A172 cells, BeSO4 produced a G0/G1-phase cell cycle arrest and increased expression of senescence-associated β-galactosidase, an enzymatic marker of senescence. BeSO4 caused phosphorylation of serine-15 of p53, accumulation of p53 protein, and expression of p21, the cyclin-dependent kinase inhibitor that is prominent during senescence. BeSO4 inhibited A172 growth with an IC50 = 4.7 μM in a 6-day proliferation assay. In contrast, BeSO4 had no effect on RKO cells, even though Be2+ uptake was similar for the two cell types. This differential responsiveness marks BeSO4 as a reagent capable of activating a separable branch of the p53 signaling network. A172 and RKO cells are known to exhibit p53-dependent upregulation of p21 in response to DNA damage. The RKO cells produced high levels of p21 when exposed to DNA damaging agents, yet failed to express p21 when treated with BeSO4. Conversely, BeSO4 did not cause DNA damage in A172 cells, yet it was a potent inducer of p21 expression. These observations indicate that the growth control pathway affected by BeSO4 is distinct from the DNA damage response pathway, even though both ultimately converge on p53 and p21.