Exposure of environmental trace elements in prostate cancer patients: A multiple metal analysis

Prostate cancer (PCa) is the second leading cause of cancer-related deaths among men. To elucidate the connection between trace elements (arsenic: As, cadmium: Cd, lead: Pb, chromium: Cr, and nickel: Ni) and the risk of PCa, we analyzed trace element levels in the serum, urine, and tissues of PCa patients, while also examining their smoking status. We correlated these levels with their smoking habits. Notably, levels of Cd (P ≤ 0.05) and As (P ≤ 0.01) were significantly higher in the tumor tissue than in adjacent tissues. No significant differences were observed in the levels of Pb, Cr and Ni. Additionally, urinary Cd levels in 70% and arsenic levels in 2.3% of the PCa cohort were markedly higher than the CDC-reported cutoff (Cd ≤ 0.185 μg/L & As ≤100 μg/L). None displayed elevated levels of urinary Pb, Cr, and Ni. Conversely, in serum samples, the concentration of arsenic exceeded the CDC-determined limit (As ≤1.0 μg/L) in 31.69% of PCa patients. However, only 7.04% of patients had higher serum Cd levels than the CDC standard values (Cd ≤ 0.315 μg/L), while all PCa patients exceeded the Cr CDC limit (Cr ≤ 0.16 μg/L) and the Ni CDC limit (Ni ≤ 0.2 μg/L). On the contrary, no significant differences were observed in serum Pb (Pb ≤ 35.0 μg/L). Our findings establish a positive link between Cd and arsenic tissue concentrations and the risk of PCa. Subsequent studies are essential to determine whether elevated trace element levels pose a risk for the development of prostate carcinogenesis. Interestingly, among the PCa cohort comprising smokers, notably higher Cd levels were observed only in tumor tissues (P ≤ 0.01) and urine (P ≤ 0.05) compared to other elements or in other specimens.

Molecular interplay between NOX1 and autophagy in cadmium-induced prostate carcinogenesis

Chronic exposure to cadmium (Cd), a class I carcinogen, leads to malignant transformation of normal prostate epithelial cells (RWPE-1). The constant generation of Cd-induced ROS and resulting ER stress induces cellular responses that are needed for cell survival, and autophagy has an important role in this process. However, the mechanisms that regulate Cd-induced ROS and how these differ in terms of acute and chronic cadmium exposure remain unexplained. Here, we show that acute or chronic Cd exposure facilitates NOX1 assembly by activating its cytosolic regulators p47phox and p67phox in RWPE-1 cells. Upregulation of NOX1 complex proteins and generation of ROS activates unfolded protein response (UPR) via phosphorylation of protein kinase RNA-like endoplasmic reticulum kinase (PERK), eukaryotic initiation factor 2 alpha (eIF2α), and selective translation of activating transcription factor 4 (ATF4). Chronic Cd exposure constantly activates NOX1 complex and generates consistent ROS and ER stress that led to defective autophagy, wherein ATG5 expression is downregulated in contrast to acute Cd exposure. As a result, selective/defective autophagy creates depletion of autophagosome-lysosome fusion that gives a survival advantage to transforming cells, which is not available to RWPE-1 cells acutely exposed to Cd. Knockdown of key molecules in a lockstep manner directly affects the most downstream autophagy pathways in transforming cells. Overall, this study demonstrates that assembly of NOX1 complex proteins is indispensable for Cd-induced persistent ROS and controls ER stress-induced defective autophagy in mice and humans.

Antiandrogen-Equipped Histone Deacetylase Inhibitors Selectively Inhibit Androgen Receptor (AR) and AR-Splice Variant (AR-SV) in Castration-Resistant Prostate Cancer (CRPC)

Background: Epigenetic modification influences androgen receptor (AR) activation, often resulting in prostate cancer (PCa) development and progression. Silencing histone-modifying enzymes (histone deacetylases-HDACs) either genetically or pharmacologically suppresses PCa proliferation in preclinical models of PCa; however, results from clinical studies were not encouraging. Similarly, PCa patients eventually become resistant to androgen ablation therapy (ADT). Our goal is to develop dual-acting small molecules comprising antiandrogen and HDAC-inhibiting moieties that may overcome the resistance of ADT and effectively suppress the growth of castration-resistant prostate cancer (CRPC). Methods: Several rationally designed antiandrogen-equipped HDAC inhibitors (HDACi) were synthesized, and their efficacy on CRPC growth was examined both in vitro and in vivo. Results: While screening our newly developed small molecules, we observed that SBI-46 significantly inhibited the proliferation of AR+ CRPC cells but not AR- CRPC and normal immortalized prostate epithelial cells (RWPE1) or normal kidney cells (HEK-293 and VERO). Molecular analysis confirmed that SBI-46 downregulated the expressions of both AR+ and AR-splice variants (AR-SVs) in CRPC cells. Further studies revealed the downregulation of AR downstream (PSA) events in CRPC cells. The oral administration of SBI-46 abrogated the growth of C4-2B and 22Rv1 CRPC xenograft tumors that express AR or both AR and AR-SV in xenotransplanted nude mice models. Further, immunohistochemical analysis confirmed that SBI-46 inhibits AR signaling in xenografted tumor tissues. Conclusion: These results demonstrate that SBI-46 is a potent agent that inhibits preclinical models of CRPC by downregulating the expressions of both AR and AR-SV. Furthermore, these results suggest that SBI-46 may be a potent compound for treating CRPC.

Urolithin A analog inhibits castration-resistant prostate cancer by targeting the androgen receptor and its variant, androgen receptor-variant 7

We investigated the efficacy of a small molecule ASR-600, an analog of Urolithin A (Uro A), on blocking androgen receptor (AR) and its splice variant AR-variant 7 (AR-V7) signaling in castration-resistant prostate cancer (CRPC). ASR-600 effectively suppressed the growth of AR+ CRPC cells by inhibiting AR and AR-V7 expressions; no effect was seen in AR- CRPC and normal prostate epithelial cells. Biomolecular interaction assays revealed ASR-600 binds to the N-terminal domain of AR, which was further confirmed by immunoblot and subcellular localization studies. Molecular studies suggested that ASR-600 promotes the ubiquitination of AR and AR-V7 resulting in the inhibition of AR signaling. Microsomal and plasma stability studies suggest that ASR-600 is stable, and its oral administration inhibits tumor growth in CRPC xenografted castrated and non-castrated mice. In conclusion, our data suggest that ASR-600 enhances AR ubiquitination in both AR+ and AR-V7 CRPC cells and inhibits their growth in vitro and in vivo models.

A small molecule inhibitor of Notch1 modulates stemness and suppresses breast cancer cell growth

Although breast cancer stem cells (BCSCs) are well characterized, molecularly targeting and eradicating this sub-population remains a challenge in the clinic. Recent studies have explored several signaling pathways that govern stem cell activation: We and others established that the Notch1 signaling plays a significant role in the proliferation, survival, and differentiation of BCSCs. Earlier, we reported that a newly developed small molecule, ASR490, binds to the negative regulatory region (NRR: The activation switch of the Notch receptor) of Notch1. In vitro results demonstrated that ASR490 significantly inhibited BCSCs (ALDH⁺ and CD44⁺/CD24^-) and breast cancer (BC) growth at nM concentrations, and subsequently inhibited the colony- and mammosphere-forming abilities of BCSCs and BCs. ASR490 downregulated the expressions of Notch1 intracellular domain (NICD: The active form of Notch1) and its downstream effectors Hey1 and HES1. Inhibition of Notch1-NICD facilitated autophagy-mediated growth inhibition by triggering the fusion of autophagosome and autolysosome in BCSCs. ASR490 was found to be non-toxic to healthy cells as compared to existing Notch1 inhibitors. Moreover, oral administration of ASR490 abrogated BCSC and BC tumor growth in the in vivo xenograft models. Together our results indicate that ASR490 is a potential therapeutic agent that inhibits BC tumor growth by targeting and abolishing Notch1 signaling in BCSCs and BC cells.

Corrigendum: A small molecule inhibitor of Notch1 modulates stemness and suppresses breast cancer cell growth

[This corrects the article DOI: 10.3389/fphar.2023.1150774.].

Abstract 3998: Discovery of a small molecule inhibitor for triple-negative breast cancer (TNBC)

Introduction: Little progress has been made towards developing alternative therapeutic strategies for triple-negative breast cancer (TNBC). Aberrant Notch1 activation, particularly in breast cancer stem cells (BCSCs) in TNBC tumors, enhances this cancer's aggressivity and resistance and consequently contributes to the poor overall survival of patients with TNBC. In contrast, inhibition of Notch1 has been shown to suppress TNBC growth. Thus, Notch1 presents as an attractive target for inhibiting TNBC growth. This study aims to overcome the limitations of current Notch1 inhibitors and identify a more specific inhibitor.

Methods: Small molecule screening was performed using structure-activity relationship (SAR) studies, and molecular docking and isothermal calorimetric (ITC) assays were used to determine the target sites of our rationally designed Notch1 inhibitor on the Notch1 receptor. The therapeutic potential of the identified small molecule Notch1 inhibitor was determined on BCSC and TNBC (ALDH+, BCSC, ALDH-, MDA-MB-231) cell lines using molecular studies and in vivo assays.

Results: We identified ASR490, a small molecule that binds to the NRR (the activation switch of the Notch receptor) of Notch1. Molecular docking studies indicated a strong interaction between ASR490 and the NRR domain with binding energy of -52.55 kcal/mol. Residue-wise interaction analysis estimated three hydrogen-bond interactions between ASR490 and NRR residues Asn-1483, Glu-1673, and Gly-1664 mediated by water molecules. The finding was further confirmed using biophysical assays (thermal shift assay and isothermal calorimetric analysis) using recombinant Notch1 protein. In vitro results demonstrated that ASR490 significantly inhibited TNBC growth (p <0.001) at nM concentrations, with an IC50 of 760 nM at 24h. Further, the inhibitory effect was confirmed by TNBC’s colony-forming abilities. Western blot analysis confirmed that ASR490 downregulated the expressions of NICD (the active form of Notch1) and its downstream effectors Hey-1 and HES1 by ubiquitinating NRR of Notch1. ASR490 was found to be non-toxic to healthy cells. Moreover, ASR490 exhibited a maximum tolerated dose of more than 100 mg/kg body weight in mice and abrogated TNBC tumor growth in vivo xenograft models.

Conclusion: Our results demonstrate ASR490 as a potential therapeutic agent that abolishes Notch1 signaling in TNBC and BCSCs by specifically targeting Notch1 NRR. Further investigation is required for the clinical translational potential of this agent.

Citation Format: Uttara Saran, Balaji Chandrasekaran, Ashish Tyagi, Amandeep Singh, Murali K. Ankem, Arun K. Sharma, Chendil Damodaran. Discovery of a small molecule inhibitor for triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3998.

Abstract 425: Selective ubiquitination of androgen receptor and its splice variants inhibits castration resistant prostate cancer

Introduction: The primary driver of castration-resistant prostate cancer (CRPC) is the Androgen receptor (AR). Drugs such as Abiraterone or Enzalutamide that target the Ligand Binding Domain (LBD) of AR are largely ineffective on AR splice variants (AR-SVs) that lack LBD and retain the N-terminal Domain (NTD) of AR. AR continues to function through other stimuli (ex: growth factors), leading to disease relapse and progression. Moreover, AR-SVs are known to heterodimerize with AR full length (AR-FL). Hence, treatment strategies that target both AR-FL and AR-NTD are needed for the complete remission of CRPC. Through structure-activity relationship (SAR) studies based on naturally occurring Urolithin A (UroA) structure, we have developed a novel small molecule UroBoc that directly binds to the NTD and inhibits CRPC growth.

Methods: To analyze the binding of UroBoc to AR-NTD, we performed differential scanning fluorimetry and measured saturation transfer difference (STD) in NMR spectroscopic studies. In addition, we investigated the effect of UroBoc on CRPC by western blotting, immunofluorescence, Immunoprecipitation, and performed Xenograft studies in castrated/non-castrated mice models.

Results: UroBoc treatment shifted the melt temperature (ΔTm) of purified NTD by 12-15 °C (median of 13.5 °C) in differential scanning fluorimetry. Moreover, STD effects observed were 30-18%, indicating a significant binding to NTD in our NMR studies. UroBoc inhibits the growth of AR+ CRPC, including enzalutamide resistant cells, at 800nM concentration, which is 40 times lower than that of the parent compound, UroA. At this concentration, UroBoc is non-toxic to normal prostate epithelial cells or other cancer cells. Interestingly, UroBoc also inhibited AR, AR-SV and PSA expressions in AR-FL (LNCaP, C42B) and AR-V7 (22-RV1) CRPC cell lines. Molecular studies suggested that UroBoc selectively promotes ubiquitination and subsequent degradation of AR and AR-V7 by proteasome activation. Remarkably, UroBoc failed to inhibit AKT, mTOR, PTEN and hormonal receptors such as estrogen and progesterone receptors suggesting AR could be a direct target for UroBoc. Further, in vivo studies revealed that oral administration of UroBoc inhibits tumor growth in CRPC in both castrated and non-castrated mice models.

Conclusion: Our results suggest that the novel UroBoc selectively degrades AR, AR-SV and overcomes enzalutamide resistance in preclinical CRPC models. We believe performing PK/PD studies will confirm the translation potential of UroBoc as a therapy for CRPC.

Citation Format: Ashish Tyagi, Balaji Chandrasekaran, Uttara Saran, Murali K. Ankem, Nikolay Dokholyan, Jyh M. Lin, Arun K. Sharma, Chendil Damodaran. Selective ubiquitination of androgen receptor and its splice variants inhibits castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 425.

Abstract 1527: Developing a multifaceted approach to target androgen receptor (AR) in castration resistant prostate cancer

Androgen receptor (AR) signaling is also regulated epigenetically by histone-modifying enzymes (histone deacetylases-HDACs) that result in the development and progression of prostate cancer (CaP). It has been established that the inhibition of HDACs suppresses CaP proliferation by inhibiting AR signaling via multiple mechanisms, including AR degradation. Hence, the goal of this study was to develop small molecules that employ multiple mechanisms to inhibit AR expression and promote its degradation, which would effectively control the emergence and treatment of castration-resistant prostate cancer (CRPC). Several rationally designed antiandrogen equipped HDAC inhibitors (HDACis) were synthesized, and their efficacy on CRPC growth was examined both in vitro and in vivo models. Results demonstrated that these compounds' target (HDAC and AR) binding properties translated into potent anticancer activity against AR+ CRPC cell lines and to a lesser extent in AR- CRPC cell lines. In addition, among these compounds, we found that SB-146, a nontoxic agent, not only inhibited the growth of AR+ CRPC cells at nanomolar IC50s without sparing toxicity to healthy prostate epithelial cells. Molecular analysis confirmed SB-146 downregulated the expressions of both AR and AR-spice variants (AR-SV) in CRPC cells. Further analyses revealed downregulation of AR downstream (PSA, HOXB13 and FOXA1) targets as well as AR-SV’s (NUP210 and SLC3A2) in CRPC cells. SB-146 was also able to overcome DHT-induced AR and AR-SV signaling in C4-2B and 22Rv1 cells. Assessment of SB-146’s therapeutic efficacy on in vivo models revealed that oral administration of this compound abrogated AR+ and AR-SV (C4-2B and 22Rv1) tumor growth in xenotransplanted nude mice models. Finally, immunohistochemical analysis confirmed SB-146’s target of both AR and AR-SVs on xenografted tumor tissues. Together these results confirm that SB-146 is a potent agent that inhibits AR signaling in CRPC cells.

Citation Format: Uttara Saran, Balaji Chandrasekaran, Ashish Tyagi, Subhasish Tapadar, Bocheng Wu, Oyelere Adegboyega, Chendil Damodaran. Developing a multifaceted approach to target androgen receptor (AR) in castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1527.

Abstract 745: Molecular landscape of arsenic-induced bladder carcinogenesis

Introduction: Epidemiological, pre-clinical, and clinical studies have linked chronic arsenic (sodium arsenite: NaAsO2) exposure to a myriad of adverse health dysfunctions including the development of bladder cancer (BCa). However, most of the studies on arsenic-induced BCa have been performed on either unsuitable cell lines or using a higher concentration of arsenic (mM), which does not reflect exposure levels in a real-world setting. We used the telomerase reverse transcriptase (HU-hTERT1) immortalized normal bladder epithelial and a median physiological concentration of NaAsO2 (250 nM: 33 mg/L), to determine the transcriptomic and phenotypic changes during malignant transformation of HU-hTERT1 cells.

Methods: HU-hTERT1 cells were exposed to 250nM arsenic for 12 months. To analyze the effect of arsenic exposure we performed cell viability, cellular proliferation, and clonogenic assays. RNA Seq data was used to perform pathway enrichment analysis, Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, and protein-protein interaction (PPI) studies.

Results: BCa patients had significantly higher (4-5 fold) levels of arsenic (20-50 mg/L) in their urine when compared to their healthy counterparts (<8 mg/L). Acute exposure to high concentration of (> 400nM) inhibited the HU-hTERT1 growth, whereas concentrations less than 400nM did not adversely affect the viability of these cells. HU-hTER1 cells began forming colonies after six months of chronic NaAsO2 exposure, with the number of colonies increasing concurrently with the exposure time. GO and KEGG analysis showed a total of 2174 genes that are differentially expressed in arsenic-treated HU-hTER1 transforming cells (0 vs 12 months). The upregulated genes (1392) were involved in cellular response to unfolded protein, response to endoplasmic reticulum stress, proteasome-mediated ubiquitin-dependent protein degradation, autophagy signaling, and tumor angiogenesis(P<0.05). Interestingly, the PPI analysis demonstrated a significant upregulation in histone modification of genes. These genes were enriched for the binding sites of transcription factors that are key regulators of carcinogenic pathways including ataxia-telangiectasia mutated (ATM) kinase and cell cycle regulatory pathways demonstrating a novel link between NaAsO2 exposure and BCa.

Conclusion: An in vitro model of NaAsO2-induced malignant transformation was developed. Identifying precise molecular events that lead to arsenic-induced malignant transformation of normal urothelial cells would be an important step in defining therapy for BCa.

Citation Format: Ajit Kumar Navin, Vaibhav Shukla, Balaji Chandrasekaran, Ashish Tyagi, Uttara Saran, Murali K. Ankem, Chendil Damodaran. Molecular landscape of arsenic-induced bladder carcinogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 745.

Abstract 2999: Activation of NFKB is responsible for defective autophagy in cadmium-induced transformation of prostate cells

Background: Evidence from the epidemiological, laboratory and clinical studies suggest that chronic exposure to cadmium (Cd) leads to the development and progression of prostate cancer (CaP). Previously, we reported defective autophagy due to upregulation of Placenta Specific 8 (Plac8) (a phagosome and lysosome fusion regulator) is responsible for Cd-induced transformation of normal prostate epithelial cells. This study mechanistically dissects the upstream signaling that regulates Plac8 function, which drives defective autophagy during Cd-induced transformation.

Methods: To examine the molecular interaction between NFκB and Plac8, we developed NFκB/Plac8 overexpression and knockdown in normal prostate epithelial cells (RWPE-1) and cadmium transformed prostate epithelial cells lines (CTPE). In addition, we performed phenotypic, and molecular analysis including promoter-based studies, western blot, and in vivo analysis to determine the interaction between Plac8 and p65 in Cd-exposed prostate epithelial cells.

Results: Our results confirmed that overexpression of Plac8 in normal prostate epithelial cells mimics Cd-transformed prostate cells (CTPE) and induces defective autophagy by regulating autophagy-related genes (ATGs) and an enhanced autophagic flux. Conversely, either NFκB or Plac8 knockdown in CTPE cells abrogates autophagy signaling. Further, Cd-exposure failed to induce defective autophagy signaling in transformed cells. Silencing p65 either by genetically or pharmacological inhibitors downregulated Plac8 expression and its survival function in CTPE cells. Hence, we investigated the interaction between NFκB and Plac8 by promoter-based analysis. We found NFκB binding site in the Plac8 promoter, and mutating NFκB binding sites in the Plac8 promoter showed a decline in luciferase activity confirming our hypothesis that NFκB activation is necessary for Plac8 activation and autophagy signaling in CTPE cells. Finally, we confirmed that silencing Plac8 significantly inhibited the tumor growth of CTPE cells compared to vehicle control. Our ongoing studies on xenotransplanted stably knockdown of p65 in CTPE cells may confirm that NFκB activation is responsible for Plac8 function and tumor growth in mice models.

Conclusion: In conclusion, our results suggest that NFκB transcriptionally regulates Plac8 function, which drives pro-survival autophagy signaling in Cd-transformed prostate epithelial cells.

Citation Format: Vaibhav Shukla, Ashish Tyagi, Venkatesh Kolluru, Uttara Saran, Balaji Chandrasekaran, Murali K. Ankem, Chendil Damodaran. Activation of NFKB is responsible for defective autophagy in cadmium-induced transformation of prostate cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2999.

Diagnostic molecular markers predicting aggressive potential in low-grade prostate cancer

Currently, clinicians rely on clinical nomograms to stratify progression risk at the time of diagnosis in patients with prostate cancer (CaP). However, these tools may not accurately distinguish aggressive potential in low-grade CaP. The current study determined the diagnostic potential of 3 molecular markers (ROCK1, RUNX3, and miR-301a) in terms of their ability to identify which low-grade tumors are likely to progress. Real-time PCR and immunohistochemical analysis were used to assess ROCK1, RUNX3, and miR-301a expression profiles in 118 serum and needle biopsy specimens. Expressions of ROCK1 and miR-301a were found to be significantly higher in Gleason 6 and 7 CaP as compared to BPH, while an inverse trend was observed with RUNX3. Further, incorporation of all 3 molecular markers significantly improved clinical nomograms' diagnostic accuracy and correlated with disease progression. Hence, in conclusion, the inclusion of these 3 molecular markers identified aggressive phenotype and predicted disease progression in low-grade CaP tumors at the time of diagnosis.

The role of autophagy in metal-induced urogenital carcinogenesis

Environmental and/or occupational exposure to metals such as Arsenic (As), Cadmium (Cd), and Chromium (Cr) have been shown to induce carcinogenesis in various organs, including the urogenital system. However, the mechanisms responsible for metal-induced carcinogenesis remain elusive. We and others have shown that metals are potent inducers of autophagy, which has been suggested to be an adaptive stress response to allow metal-exposed cells to survive in hostile environments. Albeit few, recent experimental studies have shown that As and Cd promote tumorigenesis via autophagy and that inhibition of autophagic signaling suppressed metal-induced carcinogenesis. In light of the newly emerging role of autophagic involvement in metal-induced carcinogenesis, the present review focuses explicitly on the mechanistic role of autophagy and potential signaling pathways involved in As-, Cd-, and Cr-induced urogenital carcinogenesis.

ASR490, a Small Molecule, Overrides Aberrant Expression of Notch1 in Colorectal Cancer

Notch1 activation triggers significant oncogenic signaling that manifests as enhanced metastatic potential and tumorigenesis in colorectal cancer. Novel small-molecule inhibitors, mainly plant-derived analogs, have low toxicity profiles and higher bioavailability. In this study, we have developed a small molecule, ASR490, by modifying structure of naturally occurring compound Withaferin A. ASR490 showed a growth-inhibitory potential by downregulating Notch1 signaling in HCT116 and SW620 cell lines. Docking studies and thermal shift assays confirmed that ASR490 binds to Notch1, whereas no changes in Notch2 and Notch3 expression were seen in colorectal cancer cells. Notch1 governs epithelial-to-mesenchymal transition signaling and is responsible for metastasis, which was abolished by ASR490 treatment. To further confirm the therapeutic potential of ASR490, we stably overexpressed Notch1 in HCT-116 cells and determined its inhibitory potential in transfected colorectal cancer (Notch1/HCT116) cells. ASR490 effectively prevented cell growth in both the vector (P = 0.005) and Notch1 (P = 0.05) transfectants. The downregulation of Notch1 signaling was evident, which corresponded with downregulation of mesenchymal markers, including N-cadherin and β-catenin and induction of E-cadherin in HCT-116 transfectants. Intraperitoneal administration of a 1% MTD dose of ASR490 (5 mg/kg) effectively suppressed the tumor growth in control (pCMV/HCT116) and Notch1/HCT116 in xenotransplanted mice. In addition, downregulation of Notch1 and survival signaling in ASR-treated tumors confirmed the in vitro results. In conclusion, ASR490 appears to be a potent agent that can inhibit Notch1 signaling in colorectal cancer.

ASR488, a novel small molecule, activates an mRNA binding protein, CPEB1, and inhibits the growth of bladder cancer

Due to a lack of mechanistic insights, muscle-invasive bladder cancer (MIBC) remains incurable and is one of the most lethal types of cancer in the United States. The present study investigated changes in the molecular signatures of MIBC cells (TCCSUP and HT1376) after treatment with a novel small molecule, ASR488, to gain knowledge of the mechanisms that inhibited MIBC cell growth. ASR488 treatment initiated apoptotic signaling in MIBC cells. Pathway enrichment analysis was used to analyze the changes in function of differentially expressed genes. Gene Ontology analysis, as well as Kyoto Encyclopedia of Genes and Genomes analysis, was also performed. These analyses along with reactome pathway enrichment analyses indicated that the genes upregulated in the ASR488-treated cells are involved in focal adhesion, neurotrophin signaling, p53 signaling, endoplasmic reticulum functioning in terms of protein processing, and pathways related to bladder cancer. The genes downregulated in ASR488-treated MIBC cells were mainly involved in DNA replication, mismatch repair, RNA degradation, nucleotide excision repair and TGFβ signaling (P<0.05). Furthermore, reverse transcription-quantitative PCR analysis revealed an increase in transcripts of the most upregulated genes in ASR 488-treated MIBC cells: CPEB1 (36-fold), IL11 (30-fold), SFN (20.12-fold) and CYP4F11 (15.8-fold). In conclusion, the analysis of biological functions of the most differentially expressed genes revealed possible mechanisms that may be associated with the aggressiveness of MIBC.

Chronic exposure to cadmium induces a malignant transformation of benign prostate epithelial cells

Epidemiological evidence suggests that cadmium (Cd) is one of the causative factors of prostate cancer, but the effect of Cd on benign prostatic hyperplasia (BPH) remains unclear. This study aimed to determine whether Cd exposure could malignantly transform BPH1 cells and, if so, to dissect the mechanism of action. We deciphered the molecular signaling responsible for BPH1 transformation via RNA-sequencing and determined that Cd induced the expression of zinc finger of the cerebellum 2 (ZIC2) in BPH1 cells. We noted Cd exposure increased ZIC2 expression in the Cd-transformed BPH1 cells that in turn promoted anchorage-independent spheroids and increased expression of stem cell drivers, indicating their role in stem cell renewal. Subsequent silencing of ZIC2 expression in transformed cells inhibited spheroid formation, stem cell marker expression, and tumor growth in nude mice. At the molecular level, ZIC2 interacts with the glioma-associated oncogene family (GLI) zinc finger 1 (GLI1), which activates prosurvival factors (nuclear factor NFκB, B-cell lymphoma-2 (Bcl2), as well as an X-linked inhibitor of apoptosis protein (XIAP)) signaling in Cd-exposed BPH1 cells. Conversely, overexpression of ZIC2 in BPH1 cells caused spheroid formation confirming the oncogenic function of ZIC2. ZIC2 activation and GLI1 signaling induction by Cd exposure in primary BPH cells confirmed the clinical significance of this oncogenic function. Finally, human BPH specimens had increased ZIC2 versus adjacent healthy tissues. Thus, we report direct evidence that Cd exposure induces malignant transformation of BPH via activation of ZIC2 and GLI1 signaling.

Abstract 4266: Endoplasmic reticulum (ER), a potential therapeutic target for mutant p53 colorectal cancer

Introduction: Inactivating p53 mutations contribute to tumor progression and treatment-resistance, resulting in poor patient survival in colorectal cancer patients (CRC). The goal of this study is to identify novel small molecules that therapeutically target mutant p53 in CRC.

Methods: We analyzed the effects of small molecule (ASR458) on p53-wild type (p53-wt; HCT116) and mutant p53 (p53-mut; SW620) colon cancer cells by phenotypic, molecular and in vivo assays.

Results: ASR458 treatment significantly inhibited the proliferation of both HCT116 and SW620 cells at nM concentrations. In p53-wt HCT116 cells, ASR458 caused induction of p53 that resulted in caspase-mediated cell death in both in vitro and in vivo models. On the contrary, ASR458 treatment induced ER-stress signaling (i.e., phosphorylation of ERK and eIF2-α) in p53-mut SW620 cells, which triggered ATF4 activation and subsequent induction of cascade of autophagy events (Atg family proteins, LC3B and Lamp1), causing autophagy-mediated cell death. Silencing ER stress marker ATF-4, a key regulator of autophagy, caused resistance to ASR458 and abrogated autophagy signaling in SW620 cells. This suggested that induction of ER-stress is critical for the cytotoxic effects of ASR458 in p53-mut CRC. Preliminary knockdown studies indicate that silencing of ER markers causes resistance to ASR458 in vitro, further confirming ER-stress as the mechanism of ASR458 action in p53-mut CRC. ASR458 significantly inhibited the growth of SW620 tumors in xenograft. Tissue analysis confirmed the ER-stress signaling observed in vitro.

Conclusion: Our results demonstrate ASR458 as a potential therapeutic agent with distinct targets in p53-wt and p53-mut CRC. This study also suggests that ATF4 mediated autophagy in unmanaged ER stress can reduce CRC pathogenesis. Further investigation into the pharmacokinetics and pharmacodynamics of ASR458 should help clinical translation of this agent.

Citation Format: Ashish Tyagi, Balaji chandrasekaran, Venkatesh Kolluru, Becca V. Baby, Alatassi Houda, Srinivasa Ramisetti, Arun Sharma, Murali Ankem, Chendil Damodaran. Endoplasmic reticulum (ER), a potential therapeutic target for mutant p53 colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4266.

The chemopreventive effect of withaferin A on spontaneous and inflammation-associated colon carcinogenesis models

Chemopreventive effects and associated mechanisms of withaferin A (WA) against intestinal and colon carcinogenesis remain unknown. We investigated the chemopreventive effect of WA on transgenic adenomatous polyposis coli (APCMin/+) mouse and chemically induced azoxymethane/dextran sodium sulfate (AOM/DSS) models of intestinal and colon carcinogenesis. Oral WA administration (4 and 3 mg/kg) inhibited tumor initiation and progression of intestinal polyps formation in APCMin/+ mice and colon carcinogenesis in the AOM/DSS mouse model. WA-administered mice showed a significant reduction in both number [duodenum, 33% (P > 0.05); jejunum, 32% (P < 0.025); ileum, 43% ( P < 0.001); and colon 59% (P < 0.01] and size of polyps in APCMin/+ mice compared with the respective controls. Similarly, tumor multiplicity was significantly reduced (P < 0.05) in the colon of WA-administered AOM/DSS mice. Pathological analysis showed reduced adenomas and tissue inflammation in WA-administered mouse models. Molecular studies suggested that WA inhibited the expression of inflammatory (interluekin-6, tumor necrosis factor-alpha and cyclooxygenase-2), pro-survival (pAKT, Notch1 and NF-κB) markers in APCMin/+ and AOM/DSS models. The results suggest that WA is a potent agent for preventing colon carcinogenesis and further investigation is required to show clinical utility of the agent.

Profiling of differentially expressed genes in cadmium-induced prostate carcinogenesis

The aim of the present study was to investigate the genetic signatures of cadmium-transformed prostate epithelial (CTPE) cells and to identify the potential molecular signaling involved in their malignant transformation. The dataset contained normal prostate epithelial (RWPE-1) and CTPE cells. To further examine the biological functions of the identified differentially expressed genes (DEGs), Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Reactome pathway enrichment analyses were performed. In total, 2357 DEGs were identified, including 1083 upregulated genes and 1274 downregulated genes. GO, KEGG, and Reactome pathway enrichment analyses indicated that upregulated genes were significantly enriched in ECM-receptor, focal adhesion, TGFβ signaling, and syndecan interactions, while downregulated genes were mainly involved in cell cycle regulation, arachidonic acid metabolism, oxidative phosphorylation, and folate biosynthesis (p < .05). The top upregulated (SATB1 (p < .0001), EYA2 (p < .0001) and KPNA7 (p < .0027)) and downregulated (PITX2 (p < .0007), PDLIM4 (p < .0020) and FABP5 (p < .0007)) genes were further validated via qRT-PCR analysis. In conclusion, the present study profiled DEGs in RWPE-1 and CTPE cells and identified gene pathways that may be associated with malignant transformation and tumor progression.

Combination of androgen receptor inhibitor and cisplatin, an effective treatment strategy for urothelial carcinoma of the bladder

PURPOSE

The role of androgen receptor (AR) signaling in bladder cancer (BCa) is not fully characterized. This study aimed to delineate the role of AR signaling in BCa and to determine whether the combination of AR inhibitor, Enzalutamide (Enz), and Cisplatin (Cis) efficiently inhibit the growth of BCa cells.

METHODS

AR expression was determined in 89 human urothelial BCa specimens by immunohistochemistry. A panel of BCa cell lines was treated with Cis, Enz, or a combination of both (Enz + Cis). We determined the expression of AR, changes in apoptotic signaling, DNA damage, and analyzed effect on epithelial mesenchymal transformation markers.

RESULT

AR expression was detected in 61.4% of tumors from male BCa patients. Inhibition of AR signaling by Enz effectively inhibited the growth of AR⁺ BCa cells by inducing apoptosis (26%) in AR⁺ TCCSUP (P = 0.0201) and J82 (15%, P = 0.0386) cells. Interestingly, Enz + Cis synergistically inhibited the proliferation of BCa cells even at low concentrations by inducing proapoptotic signaling in AR⁺ BCa cells. Invasive and migratory potential of TCCSUP and J82 cells were reduced with Enz + Cis treatment, and associated with down-regulation of mesenchymal markers.

CONCLUSIONS

A high percentage of the bladder tumors from male patients in our cohort expressed AR. The combination of Enz and Cis synergistically inhibited growth of BCa cells more efficiently than single agent alone. This supports the rationale for future investigation of AR antagonists in combination with standard chemotherapy in MIBC.

miR-301a expression: Diagnostic and prognostic marker for prostate cancer

BACKGROUND

Prostate-specific antigen screening for prostate cancer (CaP) remains controversial. This study establishes the role of microRNA 301a (miR-301a) as a supplemental biomarker that can distinguish between patients with benign prostate hyperplasia and clinically significant CaP. We evaluate the ability of miR-301a to predict the adverse pathology of CaP.

METHODS

In the first cohort, serum and prostate tumor samples were obtained from thirteen patients with Benign prostate hyperplasia (BPH), twelve patients with Gleason 6, and sixteen patients with Gleason 7 prostate adenocarcinoma. In the second cohort, 40 prostatectomy cases were selected (BPH:12, Gleason 6:12 and Gleason 7:16). MiRNA was extracted from serum and tumor samples. Quantitative reverse transcription-polymerase chain reaction was performed for detection of miR-301a. To understand the molecular role of miR-301a, we performed cell viability, Western blots, promoter analysis, overexpression, and silencing studies in BPH and DU-145 cell lines.

RESULTS

MiR-301a demonstrated a significantly higher expression in both serum and tumor tissue in patients with CaP when compared to patients with BPH (P = 0.011 and 0.013 for serum and tissue expression, respectively). Expression of miR-301a in prostatectomy specimens correlated with increased Gleason score. We demonstrated that miR-301a inhibited the pro-apoptotic function of RUNX3, and activated ROCK1-mediated pro-survival signal in CaP. Silencing miR-301a initiated the pro-apoptotic function of RUNX3 by inhibiting ROCK1 expression in CaP cells.

CONCLUSIONS

Expression of miR-301a could be a valuable adjunct tool for stratifying patients with elevated prostate-specific antigen, as well as those diagnosed with CaP. Including the miR-301a as an additional variable in MSKCC post-prostatectomy nomogram improved its ability in facilitating clinical decision-making.

A natural molecule, urolithin A, downregulates androgen receptor activation and suppresses growth of prostate cancer

Androgen ablation therapy is the primary therapeutic option for locally advanced and metastatic castration-resistant prostate cancer (CRPC). We investigated therapeutic effect of a dietary metabolite Urolithin A (UroA) and dissected the molecular mechanism in CRPC cells. Treatment with UroA inhibited cell proliferation in both androgen receptor-positive (AR⁺ ) (C4-2B) and androgen receptor-negative (AR^- ) (PC-3) cells however, AR⁺ CaP cells were more sensitive to UroA treatment as compared with AR^- CaP cells. Inhibition of the AR signaling was responsible for the UroA effect on AR⁺ CaP cells. Ectopic expression of AR in PC-3 cells sensitized them to UroA treatment as compared to the vector-expresseing PC-3 cells, which suggests that AR could be a target of UroA. Similarly, in enzalutamide-resistant C4-2B cells, a downregulation of AR expression also suppressed cell proliferation which was observed with the UroA treatment. Oral administration of UroA significantly suppressed the growth of C4-2B xenografts (P = 0.05) compared with PC-3 xenografts (P = 0.069) without causing toxicity to animals. Immunohistochemistry analysis confirmed in vitro findings such as downregulation of AR/pAKT signaling in UroA-treated C4-2B tumors, which suggests that UroA may be a potent chemo-preventive and therapeutic agent for CRPC.

Suppression of Notch1 and AKT mediated epithelial to mesenchymal transition by Verrucarin J in metastatic colon cancer

Epithelial to mesenchymal transition (EMT) in colorectal cancer (CRC) has been attributed to activation of AKT and Notch1 signaling pathways. As EMT corresponds to increased aggressiveness of CRC, approaches that prevent metastasis by targeting AKT/Notch1 pathways are at the forefront of current research paradigms. This study examined the anti-metastatic potential of Verrucarin J (VJ), a small molecule, in CRC cells overexpressing AKT and Notch1. VJ significantly inhibited AKT/HCT 116 cell growth by acting on the AKT/NFκB/Bcl-2 signaling axis and initiated apoptotic signaling as was evident from increased expression of pro-apoptotic markers such as cleaved PARP, cleaved caspase 3, and cleaved caspase 9. Also, VJ inhibited the cell growth in AKT/Notch1-overexpressing CRC cells and abrogated EMT. The down-regulation of AKT and Notch1 signaling was apparent in immunoblot analysis and corresponded with down-regulation of mesenchymal markers including Snail, and β-catenin. Intraperitoneal administration of VJ in control (pCMV/HCT 116) and AKT/HCT 116 mice significantly suppressed AKT-induced tumor growth in a xenograft model. In addition, down-regulation of prosurvival markers as well as AKT and Notch1 was observed in the immunohistochemical analysis of the xenografted tumors. In conclusion, our study substantiates the role of AKT and Notch1 in cell proliferation, angiogenesis, and EMT of CRC cells and demonstrates that VJ may be a viable therapeutic option to counter AKT-induced cell proliferation and tumor outgrowth in CRC.

Abstract 3930: Chemoprevention of metastatic colon cancer by a novel small molecule

Introduction: Colon cancer is a one of the leading cause of death in both men and women. Metastatic colon cancer is responsible for mortality due to resistance to conventional therapies. Our group has previously reported that activation of AKT and Notch1 plays an important role in metastasis of colon cancer cells. As Notch1 and AKT regulates cell proliferation and are upstream of epithelial to mesenchymal transition (EMT) cascade, it seems interesting to explore their inhibition for pharmacological intervention. In the present study we identified a sesquiterpene molecule, Verrucarin J (VJ), that inhibited Notch1 expression and downregulated AKT mediated EMT transition in colon cancer cells.

Methods: The anticancer effect of VJ was assessed on both colon cancer cells and stably AKT overexpressing colon cells by cell proliferation, apoptosis and Western blot analysis. For xenograft studies, pCMV/HCT-116 or AKT/HCT-116 cells (1.5 × 106) in a 50-μl final volume of phosphate-buffered saline (PBS) were injected subcutaneously into separate flanks of the mice. Also effects of VJ were determined in mouse model of colorectal cancer i.e. APC min+/_ mice. Statistical analysis was done by unpaired Student's t-test and one way ANOVA,*p≤0.05, **p≤0.01, ***p≤0.001.

Results: Molecular analysis of VJ treatment on colon cancer cells revealed that it inhibited colon cancer growth by down regulating AKT and Notch1 signaling. Western blot analysis revealed that VJ inhibits AKT/NF-κβ/ Bcl2- signaling axis in colon cancer cells. VJ also Inhibited migration and invasion of colon cancer cells that corresponds with downregulation of mesenchymal marker expression. In addition, VJ treatment induces apoptosis in colon cancer cells as well as AKT overexpressing cells. Intraperitoneal administration of VJ in pCMV/HCT116 and AKT/HCT-116 xenograft mice revealed decrease in tumor volume in comparison with control mice. We also examined the in vivo efficacy of VJ in ApcMin/+ mouse model. Treatment of ApcMin/+ with VJ (0.5 mg/kg/IP/twice a week) over 12 weeks significantly reduced the number of intestinal polyps (distal 84%; Middle 63% and Proximal 2%) as compared vehicle treated mice. In addition, we also observed 50% reduction in number of colon tumors in VJ treated mice.

Conclusion: In conclusion, our studies suggest that VJ inhibits both AKT and Notch1 signaling and induces apoptosis in colon cancer cells. In vivo studies revealed significant reduction in tumor formation in mice models of colon cancer. Hence VJ could be a viable therapeutic agent for treating patients with metastatic colon cancer.

Citation Format: Deeksha Pal, Balaji Chandrasekaran, Ashish Tyagi, Becca Von Baby, Houda Alatassi, Murali Ankem, Chendil Damodaran. Chemoprevention of metastatic colon cancer by a novel small molecule [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3930.

Abstract 3097: Chemo prevention effect of Withaferin A, a natural compound, on mouse models of colorectal carcinogenesis

Introduction: Colorectal cancer (CRC) is the most common cancer and one of the leading causes of cancer-related deaths in United States as well as worldwide. Development of sporadic CRC takes an average of 15-20 years, so establishing preventive measures are possible. We are interested in a dietary compound, Withaferin-A (WA), which possesses both chemotherapeutic and chemopreventive properties. WA's effect was studied on both colitis-mediated colon and spontaneous-intestinal carcinogenesis mouse models.

Methods: In the present study, two animal models of colon cancer were used to study the chemo- preventive effect of WA. In intestinal tumorigenesis model C57BL/6-ApcMin/+ , mice at six weeks of age were orally fed with the vehicle or WA (4mg/kg body weight of mice) for five days per week for 12-14 weeks. The other model used was AOM/DSS (Azoxymethane/dextran sulfate sodium), which induces gut inflammation and tumorigenesis. Intraperitoneal injection of AOM (8mg/kg) was followed by three cycles of DSS. WA (3mg/kg body weight of mice) was administered five times per week for 8-10 weeks. After completion of the studies, the tumor tissues were subjected to histopathological and molecular analysis. An unpaired Student's t-test was used for statistical analysis.

Results: Oral administration of WA to ApcMin/+ mice leads to a significant decrease in the number of intestinal polyps and colon tumors (colon: 42%, p=0.025), proximal: 53%, p=0.0063, middle: 27.84%, p= 0.28, distal: 32.8, p= 0.001) when compared to vehicle-treated mice. Similarly, in AOM/DSS, oral administration of WA reduced polyp multiplicity by 40% (p= 0.02) compared to vehicle-treated controls. Moreover, the treatment group of both colon cancer models showed inhibition of pro-survival signaling markers (Notch1, pAKT and NFκB) as well as a decrease in proliferative markers.

Conclusion: Our results suggest that WA effectively suppresses intestinal polyp development and colitis-mediated colon carcinogenesis, suggesting a preventive and therapeutic role in colon cancer models. These findings warrant further investigation to develop novel strategies to achieve maximum benefit of dietary agents for cancer chemoprevention.

Citation Format: Deeksha Pal, Balaji Chandrasekaran, Becca Von Baby, Houda Alatassi, Murali Ankem, Chendil Damodaran. Chemo prevention effect of Withaferin A, a natural compound, on mouse models of colorectal carcinogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3097.

Abstract 4810: Targeting androgen receptor in combination with cisplatin: Effective treatment strategy for muscle invasive bladder cancer

Background: Bladder cancer is one of the major causes of cancer death in US and worldwide. Cisplatin is a key component of chemotherapeutic regimens employed in the treatment of advanced bladder cancer. The role of androgen and androgen receptor (AR) signaling in bladder cancer remains uncharacterized.

Aim: The aim of the study is to delineate the role of AR in bladder cancer and to determine whether combination of AR inhibitor, enzalutamide (Enz) and cisplatin-based therapies effectively inhibit the growth of muscle invasive bladder cancer (MIBC).

Methods: AR expression was determined in 75 human bladder cancer specimens and in a panel of bladder cancer cell lines. Cells grown in charcoal stripped media supplemented with dihydrotestosterone (DHT) were treated with cisplatin, enzalutamide (AR inhibitor), or a combination of both. Cellular/phenotypic analysis including MTT assay, apoptotic assay, migration as well as invasion assays and molecular analysis including western blotting, real time PCR analysis were performed. Isobologram analysis for the combination was performed and analyzed with CompuSyn. Experiments were repeated in triplicates and analyzed with unpaired Student's t-test and one way ANOVA *p≤0.05, **p≤0.01, ***p≤0.001.

Results: AR expression was seen in around 40% of bladder cancer patients. Inhibition of AR signaling by enzalutamide effectively inhibited the growth of AR+ MIBC cells. Interestingly, enzalutamide in combination with cisplatin (Enz + Cis) synergistically inhibited the proliferation of MIBC cells, TCCSUP (CI: 0.42, 1.25 + 5 μM) and J82 (CI: 0.79, 2.5 + 5 μM) at low concentrations of enzalutamide and cisplatin resp.. The molecular studies revealed the induction of DNA damage markers (pATM, pATR, pChk1, pHis) and enhanced expression of the pro-apoptotic genes (Bax, caspases-3 and PARP) in Enz+Cis treated AR+ MIBC cells. In addition, we demonstrated abrogation of invasive and migratory potential with Enz+Cis treatment, by downregulation of the mesenchymal markers (N-cadherin, slug, β-catenin, and vimentin) in both cell lines. Our studies suggest combination of Enz + Cis may be effective in patients with AR+ MIBC.

Conclusion: Combination of cisplatin and AR inhibition effectively inhibit bladder tumor growth and migration, and hold promise as synergetic therapies for AR+ bladder cancer patients.

Citation Format: Ashish Tyagi, Balaji Chandersekaran, Samarpit Rai, Houda Alatassi, Ahmed Q. Haddad, Murali K. Ankem, Chendil Damodaran. Targeting androgen receptor in combination with cisplatin: Effective treatment strategy for muscle invasive bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4810.

Abstract 1328: Cadmium-induced endoplasmic reticulum stress causes defective autophagy in human prostate carcinogenesis

Introduction: Exposure to cadmium (Cd) is associated with a spectrum of human pathogenesis including the prostate cancer (CaP). A clear dose-response relation between Cd-exposure and CaP have been reported in men exposed to Cd. However, the molecular mechanism underlying the malignant cell transformation following Cd exposure is yet to be determined. One of the possible mechanisms is that Cd causes endoplasmic reticulum (ER) stress, which further induces defective autophagy that plays a cytoprotective role in response to the misfolded and unfolded proteins that are formed during cellular transformation. Hence, the goal of this study is to investigate the underlying mechanism of how Cd causes malignant cell transformation (from normal to cancer cells) and on the development of tumorigenesis by the Cd-transformed cells.

Methods: Normal prostate epithelial cells (RWPE-1) and Cd (10µM)-transforming prostate epithelial cells and cadmium-transformed prostate epithelial cells (CTPE) were utilized. Overexpression and/or silence ER-sensors, EGFR, and p62 were performed in above mention cell lines and subjected to cell viability, apoptosis, autophagy functional studies and Western blot analyses. For statistical analysis, data were analyzed using Student's ‘t' test with a p-value less than 0.05 considered significant.

Results: Our preliminary results suggest that during cellular transformation, Cd exposure induced ER-stress, which triggered the phosphorylation of stress transducers including protein kinase R-like ER Kinase (PERK) and e1F2-α (eukaryotic translation initiation factor 2A-alpha). Phosphorylation resulted in the activation of ATF4 (Activating Transcription Factor 4) and autophagy induction thus enhancing protection of Cd-damaged cells. Further, inhibition of stress inducers (ATF4) or p62 by siRNA blocked the Cd-induced defective autophagy resulted in growth inhibition in transforming cells. Interestingly, in Cd-transformed cells, blocking EGFR activation by siRNA or pharmacological inhibitors significantly inhibited the growth, but not in the transforming cells suggesting that EGFR activation plays a critical role only after cellular transformation. Further, xenograft tumor tissues generated by Cd-transformed cells expressed high levels of ATF-4, EGFR, p62 and LC3B in correlation with in vitro findings. Moreover, increased expression of the proteins (ATF-4, EGFR, p62, and LC3B) in human CaP specimens correlates with Gleason sum in comparison with benign prostatic hyperplasia and “normal” adjacent tissues.

Conclusions: The results suggest that ER stress responsible for the defective autophagy in Cd-induced transformation. This study highlights the better understanding of the complex interrelationship among prostate cancer phenotypes and the molecular, cellular, biochemical, and pathological changes associated with Cd and prostate cancer.

Citation Format: Venkatesh Kolluru, Ashish Tyagi, Balaji Chandrasekaran, Murali K. Ankem, Chendil Damodaran. Cadmium-induced endoplasmic reticulum stress causes defective autophagy in human prostate carcinogenesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1328.

Differentially Expressed mRNA Targets of Differentially Expressed miRNAs Predict Changes in the TP53 Axis and Carcinogenesis-Related Pathways in Human Keratinocytes Chronically Exposed to Arsenic

Arsenic is a widely distributed toxic natural element. Chronic arsenic ingestion causes several cancers, especially skin cancer. Arsenic-induced cancer mechanisms are not well defined, but several studies indicate that mutation is not the driving force and that microRNA expression changes play a role. Chronic low arsenite exposure malignantly transforms immortalized human keratinocytes (HaCaT), serving as a model for arsenic-induced skin carcinogenesis. Early changes in miRNA expression in HaCaT cells chronically exposed to arsenite will reveal early steps in transformation. HaCaT cells were maintained with 0/100 nM NaAsO2 for 3 and 7 weeks. Total RNA was purified. miRNA and mRNA expression was assayed using Affymetrix microarrays. Targets of differentially expressed miRNAs were collected from TargetScan 6.2, intersected with differentially expressed mRNAs using Partek Genomic Suite software, and mapped to their pathways using MetaCore software. MDM2, HMGB1 and TP53 mRNA, and protein levels were assayed by RT-qPCR and Western blot. Numerous miRNAs and mRNAs involved in carcinogenesis pathways in other systems were differentially expressed at 3 and 7 weeks. A TP53 regulatory network including MDM2 and HMGB1 was predicted by the miRNA and mRNA networks. Total TP53 and TP53-S15-phosphorylation were induced. However, TP53-K382-hypoacetylation suggested that the induced TP53 is inactive in arsenic exposed cells. Our data provide strong evidence that early changes in miRNAs and target mRNAs may contribute to arsenic-induced carcinogenesis.

What is the role of microRNA-301A expression as a diagnostic and predictive marker of biochemical recurrence for prostate cancer?

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Background: Prostate specific antigen (PSA) screening for prostate cancer (PCa) remains controversial, due to its association with an increase in overdiagnosis of clinically insignificant PCa, and overtreatment. Hence, the need for more specific biomarkers to detect PCa and determine its prognosis. MicroRNA expression has previously been demonstrated as a biomarker to detect several malignancies. Studies suggest that microRNA-301a (miR-301a) inhibits the pro-apoptotic function of RUNX3, a transcription factor, and consequently activates ROCK1-mediated survival signaling in PCa. This study establishes the role of miR-301a as a reliable biomarker that can distinguish between patients with benign prostate hyperplasia (BPH) and PCa, and predict biochemical recurrence (BCR) after definitive treatment of PCa. Methods: Serum samples and tissue from prostate biopsies were collected from patients with an elevated PSA prospectively. The expression of miR- 301a was measured via reverse transcriptase-polymerase chain reaction. Additionally, miR-301a expression was retrospectively evaluated in prostatic tissue of 50 patients with PCa, including benign tissue, and correlated with clinico-pathological characteristics to predict BCR. Immunohistochemistry was performed to confirm the molecular target of miR-301a in cancerous tissue. Results: miR-301a demonstrated a significantly higher expression (p = 0.013) in both PCa tissue (Gleason 6 & 7 PCa) and serum samples (p = 0.011) when compared to BPH. Expression of miR-301a in Gleason 6 & 7 prostatectomy specimens positively correlated with patients who developed BCR when compared to patients who did not. When compared to the current nomogram for the prediction of PCa (i.e., PSA, age, race, Gleason score, and family history), incorporation of miR-301a was associated with a superior prediction of BCR at three years post-prostatectomy. Conclusions: miR-301a expression is a valuable tool for diagnosing PCa in patients with an elevated PSA. Combining miR-301a with PSA is associated with better risk stratification of PCa patients, and may help facilitate clinical decision making.

Oral administration of withaferin A inhibits carcinogenesis of prostate in TRAMP model

We previously reported that withaferin A (WA), a natural compound, deters prostate cancer by inhibiting AKT while inducing apoptosis. In the current study, we examined its chemopreventive efficacy against carcinogenesis in the prostate using the transgenic adenocarcinoma of mouse prostate (TRAMP) model. Two distinct sets of experiments were conducted. To determine whether WA delays tumor progression, it was given before cancer onset, at week 6, and until week 44. To determine its effect after the onset of prostate cancer, it was given from weeks 12 to 35. In both strategies, oral administration of WA effectively suppressed tumor burden when compared to vehicle-treated animals. No toxicity was seen in treated animals at gross pathological examination. Western blot analysis and immunohistochemistry of tumor sections revealed that in TRAMP controls, AKT and pAKT were highly expressed while nuclear FOXO3a and Par-4 were downregulated. On the contrary, treated mice showed inhibition of AKT signaling and activation of FOX03a-Par-4-induced cell death. They also displayed inhibition of mesenchymal markers such as β-catenin, vimentin, and snail as well as upregulation of E-cadherin. Because expressions of the angiogenic markers factor VIII and retic were downregulated, an anti-angiogenic role of WA is suggested. Overall, our results suggest that WA could be a promising anti-cancer agent that effectively inhibits carcinogenesis of the prostate.

Inhibition of p53 prevents diabetic cardiomyopathy by preventing early-stage apoptosis and cell senescence, reduced glycolysis, and impaired angiogenesis

Elevated tumor suppressor p53 expression has been associated with heart diseases, including the diabetic heart. However, its precise role in the pathogenesis of diabetic cardiomyopathy (DCM) remains unclear. We hypothesized that the development of DCM is attributed to up-regulated p53-mediated both early cardiac cell death and persistent cell senescence, glycolytic and angiogenetic dysfunctions. The present study investigated the effect of p53 inhibition with its specific inhibitor pifithrin-α (PFT-α) on the pathogenesis of DCM and its associated mechanisms. Type 1 diabetes was induced with multiple low doses of streptozotocin. Both hyperglycemic and age-matched control mice were treated with and without PFT-α five times a week for 2 months and then sacrificed at 3 and 6 months post-diabetes. Treatment with PFT-α significantly prevented the progression of diabetes-induced cardiac remodeling and dysfunction (i.e., DCM). Mechanistically, the inhibition of p53 prevented the cardiac apoptosis during early-stage diabetes (0.5 month), attenuated diabetes-induced cell senescence (3 and 6 months), and improved both glycolytic and angiogenic defects by increasing hypoxia-induced factor (HIF)-1α protein stability and upregulating HIF-1α transcription of specific target genes at 3 and 6 months after diabetes. Therefore, the targeted inhibition of p53 in diabetic individuals may provide a novel approach for the prevention of DCM.

Withaferin-A suppress AKT induced tumor growth in colorectal cancer cells

The oncogenic activation of AKT gene has emerged as a key determinant of the aggressiveness of colorectal cancer (CRC); hence, research has focused on targeting AKT signaling for the treatment of advanced stages of CRC. In this study, we explored the anti-tumorigenic effects of withaferin A (WA) on CRC cells overexpressing AKT in preclinical (in vitro and in vivo) models. Our results indicated that WA, a natural compound, resulted in significant inhibition of AKT activity and led to the inhibition of cell proliferation, migration and invasion by downregulating the epithelial to mesenchymal transition (EMT) markers in CRC cells overexpressing AKT. The oral administration of WA significantly suppressed AKT-induced aggressive tumor growth in a xenograft model. Molecular analysis revealed that the decreased expression of AKT and its downstream pro-survival signaling molecules may be responsible for tumor inhibition. Further, significant inhibition of some important EMT markers, i.e., Snail, Slug, β-catenin and vimentin, was observed in WA-treated human CRC cells overexpressing AKT. Significant inhibition of micro-vessel formation and the length of vessels were evident in WA-treated tumors, which correlated with a low expression of the angiogenic marker RETIC. In conclusion, the present study emphasizes the crucial role of AKT activation in inducing cell proliferation, angiogenesis and EMT in CRC cells and suggests that WA may overcome AKT-induced cell proliferation and tumor growth in CRC.

Molecular insights: Suppression of EGFR and AKT activation by a small molecule in non-small cell lung cancer

Epidermal growth factor receptor (EGFR) activation events and the mammalian target of rampamycin (mTOR) are considered important therapeutic targets in alleviating cancer conditions. The current treatment paradigm has shifted to personalized treatment strategies with tyrosine kinase inhibitors (TKIs) or anaplastic lymphoma kinase (ALK) inhibitors, due to low survival rates in non-small cell lung cancer (NSCLC) in terms of the prevailing platinum-based therapy. In the present study, we examined the anticancer potential of Verrucarin J (VJ), a small molecule, in NSCLC cell lines (H460 and A549). The small molecule significantly inhibited cell growth, proliferation, colony forming ability, and induced apoptosis in both lung cancer cell lines. The inhibitory effects on EGFR (pEGFR –tyr1173) and AKT (pAKT Serine473) signaling, downregulates downstream pro-survival signaling (mTOR and NF-κB) in cancer cell lines. In addition, VJ abrogated invasive and migratory potential of A549 and H460 cells. We also observed a downregulation of mesenchymal markers such as N-cadherin, Slug, β-catenin, and vimentin expression in both cell lines. Our results suggest that VJ inhibited cancer cell growth and could be a potent molecule to inhibit EGFR and AKT signaling in NSCLC.

Induction of Plac8 promotes pro-survival function of autophagy in cadmium-induced prostate carcinogenesis

Chronic exposure to cadmium is known to be a risk factor for human prostate cancer. Despite over-whelming evidence of cadmium causing carcinogenicity in humans, the specific underlying molecular mechanisms that govern metal-induced cellular transformation remain unclear. Acute exposure (up to 72 h) to cadmium induces apoptosis in normal prostate epithelial cells (RWPE-1), while chronic exposure (>1 year) transforms these cells to a malignant phenotype (cadmium-transformed prostate epithelial cells; CTPE). Increased expression of autophagy-regulated genes; Plac8, LC3B and Lamp-1; in CTPE cells was associated with cadmium-induced transformation. Increased expression of Plac8, a regulator of autophagosome/autolysosome fusion, facilitates the pro-survival function of autophagy and upregulation of pAKT^(ser473) and NF-κβ, to allow CTPE to proliferate. Likewise, inhibition of Plac8 suppresses CTPE cell growth. Additionally, overexpression of Plac8 in RWPE-1 cells induces resistance to cadmium toxicity. Pharmacological inhibitors and an inducer of autophagy failed to affect Plac8 expression and CTPE cell viability, suggesting a unique role for Plac8 in cadmium-induced prostate epithelial cell transformation. These results support a role for Plac8 as an essential component in the cadmium-induced transformation of normal prostate epithelial cells to a cancerous state.

Abstract 371: Developing small molecule therapeutics to target AKT signaling in non-small cell lung cancer

Lung cancer remains a leading public health problem which is evidenced by its increasing death rate. Platinum-based chemotherapy is the first-line of treatment for patients in advanced stages of non-small cell lung cancer (NSCLC), however the success rates are not quite impressive. Hence, developing individualized treatment strategies for metastatic lung cancer gains momentum, such as Tyrosine kinase inhibitors erlotinib and gefitinib, or ALK inhibitors ceritinib and alectinib are commonly used in the clinic. Recent reports suggest that pAKT(ser473) is highly expressed in NSCLC and higher nuclear expression of pAKT correlated with poor prognosis and an independent prognostic marker for survival. Our lab is interested to develop novel small molecules which specifically inhibit AKT signaling in NSCLC. Structure-activity relationship (SAR) studies in our laboratory have recently ideintifed one such compound, AKS-407, that effectively inhibited cell growth at nanomolar concentration in NSCLC cell lines (A549 and H460; 250nM). Molecular studies revealed AKS-407 inhibited AKT signaling by down regulating pAKT(ser473) expression and downstream events including NFκB activation, BCl-2 expression in both the cell lines. As signaling through AKT regulates epithelial-mesenchymal transition (EMT) in NSCLC, we determined the effect of AKS-407 on EMT phenotype on NSCLC cells. Treatment of AKS-407 inhibited the mesenchymal markers includes snail, MMP9, N-cadherin, β-catenin and vimentin expression that resulted in blocking invasion and migration of A549 and H-460 cells. These results suggest AKS-407 to be a promising small molecule targeting AKT signaling pathway which remains an important target for the development of effective treatment of metastatic NSCLC. Validating in-vivo efficacy of this potential drug candidate would further support our overall goal of the study.

Citation Format: Balaji Chandrasekaran, Deeksha Pal, Venkatesh Kolluru, Srinivasa R. Ramisetti, Arun K. Sharma, Murali Ankem, Chendil Damodaran. Developing small molecule therapeutics to target AKT signaling in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 371. doi:10.1158/1538-7445.AM2017-371

Abstract 2903: 1-Methoxyphaseollidin: Novel gamma secretase inhibitor targeting notch-1 signaling in breast cancer stem cells

We recently showed that two different ALDH+ and CD44+/CD24-/low breast cancer stem cells (BSCSs) exhibited stem cell characteristics that include self-renewal, extensive proliferation, the ability to form non-adherent spherical clusters, chemotherapy resistance and high Notch1 expression. We have identified a compound compound: 6-(3-methylbut-2-enyl) coumestrol (Pso) and treatment with Pso resulted in growth inhibition and an EMT phenotype in both BCSCs and BC cells. Oral Pso administration at physiologically achievable doses (25 mg/kg/BW) suppressed the growth of BCSCs and BC xenografts without toxicity. In the current studies, we identified several novel Pso-derived analogs that may be more potent than the parent compound. One such compound, 1-methoxyphaseollidin (1MP), obtained via three main functional group changes: (i) translocation of the isoprenyl moiety from the phenyl ring fused to the pyran ring (as in Pso) to the phenyl ring adjacent to the furan ring, (ii) removal of the carbonyl group from the pyran ring, and (iii) introduction of a methoxy group at the 1-position, inhibited Notch1 activity and growth of both BSCS and BC cells at nM concentration (IC50: 300nM), which is 100 times more potently than Pso in cell culture models. Molecular studies suggest that 1MP inhibits Notch signaling pathways (Hes1, Hey1 and Presenilin) in both BCSC and BC cells. Further, downregulation of AKT signaling (pAKT (S473), p65 and BCl-2 were seen in 1MP treated cells. Docking studies suggest that 1MP binds outside of the catalytic unit of γ-secretase and induces a conformational change, resulting in Notch1 inhibition in both BCSCs and BC cells. More importantly, administration of 1MP significantly inhibited the growth of BCSC and BC tumors without causing gastrointestinal toxicity in tumor-bearing mice. H&E staining suggests that 1MP treated tumors show infiltrate to margins are less as compared to vehicle treated mice’s. We believe targeting notch1 signaling and optimizing 1MP could be an effective therapeutic strategy for treating breast cancer.

Note: This abstract was not presented at the meeting.

Citation Format: Venkatesh Kolluru, Deeksha Pal, Becca Baby, Houda Alatassi, Arun Kumar Sharma, Murali Ankem, Chendil Damodaran. 1-Methoxyphaseollidin: Novel gamma secretase inhibitor targeting notch-1 signaling in breast cancer stem cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2903. doi:10.1158/1538-7445.AM2017-2903

Inhibition of autophagy prevents cadmium-induced prostate carcinogenesis

BACKGROUND

Cadmium, an established carcinogen, is a risk factor for prostate cancer. Induction of autophagy is a prerequisite for cadmium-induced transformation and metastasis. The ability of Psoralidin (Pso), a non-toxic, orally bioavailable compound to inhibit cadmium-induced autophagy to prevent prostate cancer was investigated.

METHODS

Psoralidin was studied using cadmium-transformed prostate epithelial cells (CTPE), which exhibit high proliferative, invasive and colony forming abilities. Gene and protein expression were evaluated by qPCR, western blot, immunohistochemistry and immunofluorescence. Xenograft models were used to study the chemopreventive effects in vivo.

RESULTS

Cadmium-transformed prostate epithelial cells were treated with Pso resulting in growth inhibition, without causing toxicity to normal prostate epithelial cells (RWPE-1). Psoralidin-treatment of CTPE cells inhibited the expression of Placenta Specific 8, a lysosomal protein essential for autophagosome and autolysosome fusion, which resulted in growth inhibition. Additionally, Pso treatment caused decreased expression of pro-survival signalling proteins, NFκB and Bcl2, and increased expression of apoptotic genes. In vivo, Pso effectively suppressed CTPE xenografts growth, without any observable toxicity. Tumours from Pso-treated animals showed decreased autophagic morphology, mesenchymal markers expression and increased epithelial protein expression.

CONCLUSIONS

These results confirm that inhibition of autophagy by Pso plays an important role in the chemoprevention of cadmium-induced prostate carcinogenesis.

Withaferin A Inhibits Prostate Carcinogenesis in a PTEN-deficient Mouse Model of Prostate Cancer

We recently demonstrated that AKT activation plays a role in prostate cancer progression and inhibits the pro-apoptotic function of FOXO3a and Par-4. AKT inhibition and Par-4 induction suppressed prostate cancer progression in preclinical models. Here, we investigate the chemopreventive effect of the phytonutrient Withaferin A (WA) on AKT-driven prostate tumorigenesis in a Pten conditional knockout (Pten-KO) mouse model of prostate cancer. Oral WA treatment was carried out at two different doses (3 and 5 mg/kg) and compared to vehicle over 45 weeks. Oral administration of WA for 45 weeks effectively inhibited primary tumor growth in comparison to vehicle controls. Pathological analysis showed the complete absence of metastatic lesions in organs from WA-treated mice, whereas discrete metastasis to the lungs was observed in control tumors. Immunohistochemical analysis revealed the down-regulation of pAKT expression and epithelial-to-mesenchymal transition markers, such as β-catenin and N-cadherin, in WA-treated tumors in comparison to controls. This result corroborates our previous findings from both cell culture and xenograft models of prostate cancer. Our findings demonstrate that the daily administration of a phytonutrient that targets AKT activation provides a safe and effective treatment for prostate cancer in a mouse model with strong potential for translation to human disease.

Targeting aberrant expression of Notch-1 in ALDH+ cancer stem cells in breast cancer

We have previously reported that high aldehyde dehydrogenase (ALDH) enzyme activity in breast cancer cells results in breast cancer stem cell (BCSC) properties by upregualting Notch-1 and epithelial mesenchymal markers. This results in chemoresistance in breast cancer. Here, we examined the functional and clinical significance of ALDH expression by measuring the ALDH levels in breast cancer tissues by immunohistochemistry. There was a significantly higher ALDH expression in higher grade breast cancer tumor tissues (Grade- II and III) versus normal breast tissues. Injection of BCSC (ALDH⁺ and CD44⁺ /CD22^- ) cells resulted in aggressive tumor growth in athymic mice versus ALDH^- cells. The ALDH⁺ and CD44⁺ /CD22^- tumors grow rapidly and are larger than ALDH^- tumors which were slow growing and smaller. Molecularly, ALDH⁺ tumors expressed higher expression of Notch-1 and EMT markers than ALDH^- tumors. Oral administration of the naturally occurring Psoralidin (Pso, 25 mg/kg of body weight) significantly inhibited the growth in ALDH⁺ and ALDH^- tumors as well. Psoralidin inhibited Notch-1 mediated EMT activation in ALDH⁺ and ALDH^- tumors-this confirms our in vitro findings. Our results suggest that Notch-1 could be an attractive target and inhibition of Notch-1 by Psoralidin may prevent pathogenesis of breast cancer as well as metastasis. © 2016 Wiley Periodicals, Inc.

miR-301a expression: A prognostic marker for prostate cancer

PURPOSE

The diagnosis and treatment of prostate cancer (CaP) continues to be challenging, as prostate-specific antigen (PSA) appears to be overly sensitive and biopsy is the only reliable method for confirmation. Hence, the goal of the study is to identify a biomarker that could distinguish malignant cancer from benign prostatic hyperplasia (BPH) during the early diagnosis of the disease.

MATERIALS AND METHODS

A total of 75 formalin fixed paraffin embedded (FFPE) with matching controls, 4 paired metastatic tumors, 6 fresh tumor tissues and BPH (13 cases) with their clinical diagnosis were selected for this study. Prostate cancer cell lines and normal prostate epithelial cell lines were obtained from ATCC and subjected to phenotypic analysis.

RESULTS

We observed significant differential expression of miR-301a in CaP samples in comparison to BPH and adjacent benign samples. The overexpression of miR-301a activates the invasion/migration of CaP cells. In contrast, silencing miR-301a expression inhibited the colony-forming ability, adhesion, invasion and migration of CaP cells. Similarly, the overexpression of miR-301a increased cell motility in normal RWPE-1 prostate epithelial cells. Our results suggest that miR-301a is differentially expressed between BPH and CaP specimens and that the expression of miR-301a correlates with biochemical recurrence and/or metastasis in CaP patients.

CONCLUSIONS

The expression of miR-301a could be a potential marker for metastasis in CaP patients. Detecting miR-301a expression during diagnosis will avoid wait and watch timelines, thus preventing morbidity.

Abstract 5253: Oral administration of Withaferin-A effectively suppresses prostate carcinogenesis in PTEN-Knockout mice

Androgen ablation therapy alone or in combination with radiation therapy is the mainstay for prostate cancer (CaP), which is initially effective in de-bulking the tumor volume, however, eventually these patients will progress to a castration-resistant prostate cancer (CRPC), which requires more aggressive chemotherapies. Treating CRPC with second generation androgen -ablation based therapies like enzalutamide and abiraterone exhibit only a short window of therapeutic benefit resulting in chemoresistance. Hence, there is an immediate need for identification of novel targets to eradicate CRPC effectively. We and others have reported targeting AKT activation could efficiently suppress the growth of CRPC cells; in fact a number of clinical trials have shown some promise that AKT could be an attractive target for CRPC. In fact, clinical studies from our lab have suggested that AKT activation predominantly occurs in Gleason stage specific manner suggesting identification of novel drugs to inhibit AKT activation is imperative. Our earlier finding suggests that Withaferin-A (WA), an herbal molecule effectively inhibits the growth of CRPC cells by downregulating AKT activation and its downstream pro-survival events. Present study investigated whether oral administration of WA may inhibit tumor development in Pten conditional knockout mice [(Pten-loxp/loxp:PB-Cre4+) (Pten-KO)] which will be a unique and appropriate preclinical model to study the AKT driven prostate tumor. Oral administration of WA for 45 weeks effectively prevented the tumor growth without any significant signs of toxicity to organs in Pten-KO mice. Vehicle and WA (5mg/kg body weight) were orally given up to 45 weeks. Gross pathological studies suggested a significant inhibition of growth and micro metastasis in WA-treated mice as compared to the vehicle treated mice. On microscopic examination of the prostatic tissue, we found that the WA-treated tumors showed more necrosis than the control group and some of the tumors were more differentiated than the controls in the same group. All the organs were completely submitted for histological evaluation. None of the WA-treated mice organs showed any metastatic lesion on the other hand, we found discrete metastasis to lungs in the control tumors. Our ongoing immunohistochemistry analysis may corroborate our in vitro findings that down regulation of AKT and epithelial-to-mesenchymal transition (EMT) markers such as β-catenin, snail, and vimentin in WA treated tumors as compared to the control mice. Overall, these results provide important scientific evidence in support of AKT signaling as a target to inhibit CRPC as well as metastatic CRPC.

Citation Format: Chendil Damodaran, Suman Suman, Trinath P. Das, Houda Alatassi, Murali K. Ankem. Oral administration of Withaferin-A effectively suppresses prostate carcinogenesis in PTEN-Knockout mice. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5253.

Synthesis of Psoralidin derivatives and their anticancer activity: First synthesis of Lespeflorin I1

Synthetic scheme for the preparation of a number of different derivatives of anticancer natural product Psoralidin is described. A convergent synthetic approach is followed using simple starting materials like substituted phenyl acetic esters and benzoic acids. The developed synthetic route leads us to complete the first synthesis of an analogous natural product Lespeflorin I₁, a mild melanin synthesis inhibitor. Preliminary bioactivity studies of the synthesized compounds are carried out against two commonly used prostate cancer cell lines. Results show that the bioactivity of the compounds can be manipulated by the simple modification of the functional groups.

Activation of AKT negatively regulates the pro-apoptotic function of death-associated protein kinase 3 (DAPK3) in prostate cancer

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This is the first study that demonstrates the inverse correlation of AKT activation and down-regulation of tumor suppressor protein, DAPK-3, in CaP cell lines as well as human prostate tumor tissues that correlate with disease progression.

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Either silencing AKT or overexpressing DAPK-3 induces apoptosis in Castration Resistant Prostate Cancer cells.

The activation of AKT governs many signaling pathways and promotes cell growth and inhibits apoptosis in human malignancies including prostate cancer (CaP). Here, we investigated the molecular association between AKT activation and the function of death-associated protein kinase 3 (DAPK3) in CaP. An inverse correlation of pAKT and DAPK3 expression was seen in a panel of CaP cell lines. Inhibition of AKT by wortmannin/LY294002 or overexpression of DAPK3 reverts the proliferative function of AKT in CaP cells. On the other hand, ectopic expression of AKT inhibited DAPK3 function and induced proliferation of CaP cells. In addition, AKT over-expressed tumors exhibit aggressive growth when compared to control vector in xenograft models. The immunohistochemistry results revealed a down-regulation of DAPK3 expression in AKT over-expressed tumors as compared to control tumors. Finally, we examined the expression pattern of AKT and DAPK3 in human CaP specimens – the expected gradual increase and nuclear localization of pAKT was seen in higher Gleason score samples versus benign hyperplasia (BPH). On the contrary, reduced expression of DAPK3 was seen in higher Gleason stages versus BPH. This suggests that inhibition of DAPK3 may be a contributing factor to the carcinogenesis of the prostate. Understanding the mechanism by which AKT negatively regulates DAPK3 function may suggest whether DAPK3 can be a therapeutic target for CaP.

Oxidative Stress: A Promising Target for Chemoprevention

Cancer is a leading cause of death worldwide, and treating advanced stages of cancer remains clinically challenging. Epidemiological studies have shown that oxidants and free radicals induced DNA damage is one of the predominant causative factors for cancer pathogenesis. Hence, oxidants are attractive targets for chemoprevention as well as therapy. Dietary agents are known to exert an anti-oxidant property which is one of the most efficient preventive strategy in cancer progression. In this article, we highlight dietary agents can potentially target oxidative stress, in turn delaying, preventing, or treating cancer development. Some of these agents are currently in use in basic research, while some have been launched successfully into clinical trials.

Natural Products That Target Cancer Stem Cells

The cancer stem cell model suggests that tumor initiation is governed by a small subset of distinct cells with stem-like character termed cancer stem cells (CSCs). CSCs possess properties of self-renewal and intrinsic survival mechanisms that contribute to resistance of tumors to most chemotherapeutic drugs. The failure to eradicate CSCs during the course of therapy is postulated to be the driving force for tumor recurrence and metastasis. Recent studies have focused on understanding the unique phenotypic properties of CSCs from various tumor types, as well as the signaling pathways that underlie self-renewal and drug resistance. Natural products (NPs) such as those derived from botanicals and food sources may modulate vital signaling pathways involved in the maintenance of CSC phenotype. The Wingless/Integrated (WNT), Hedgehog, Notch and PI3K/AKT/mTOR pathways have all been associated with quiescence and self-renewal of CSCs, as well as execution of CSC function including differentiation, multidrug resistance and metastasis. Recent studies evaluating NPs against CSC support the epidemiological evidence linking plant-based diets with reduced malignancy rates. This review covers the key aspects of NPs as modulators of CSC fate.

Abstract 1951: Identification of novel molecular targets for treatment of castration-resistant prostate cancer

One of the major limitations of current therapies for treatment of prostate cancer is the acquisition of castration-resistance by tumor cells. Castration-resistant prostate cancer (CRPC) proceeds through multiple signaling pathways that utilize the PI3K/AKT axis to direct anti-apoptotic and pro-survival responses in CRPC cells. We performed in-depth genomic and phenotypic analysis which revealed that two transcription factors, Cyclic AMP Response Element Binding protein (CREB) and Forkhead Box O3 (FOXO3a), were inversely expressed in CRPC cells. Specifically, an upregulation of CREB in stage-specific manner in CRPC tumor cells was suggestive of its proliferative role in tumor growth. Conversely, downregulation of FOXO3a expression suggested inhibition of this transcription factor's pro-apoptotic function, which may also facilitate tumor growth. In pre-clinical models of CRPC, both CREB and FOXO3a transcriptionally regulated the function of prostate tumor suppressor, Par-4 (prostate apoptotic response gene-4).

Promoter bashing studies identified consensus regulatory target binding sites of CREB and FOXO3a on Par-4 promoter. The sequential deletion of three CREB binding sites in the Par-4 promoter relieved CREB-mediated suppression of Par-4, whereas sequential deletion of FOXO3a binding sites in Par-4 promoter abrogated Par-4 promoter activity. We further dissected upstream events of CREB and FOXO3a, which are regulated by protein kinase-B AKT using a small-molecule AKT inhibitor (SMAI) drug. Overexpression of AKT in CRPC (DU-145/AKT, C4-2B/AKT and PC-3/AKT) cells induced pro-survival machinery by activating CREB and inhibiting pro-apoptotic function of FOXO3a and resulting in resistance of cells to drug.

The in vivo efficacy of our SMAI drug was evaluated in DU-145/AKT and C4-2B/AKT tumor xenografts in nude mouse model. AKT overexpressing tumors exhibited aggressive growth rates and exhibited high vascularisation and angiogenesis as compared to vector-transfected tumors. Daily oral administration of SMAI drug significantly inhibited tumor growth in both DU-145 and C4-2B AKT-overexpressing tumors. IHC analysis of these tumor tissues revealed reduced FOXO3a expression and increased pCREB expression following treatment with SMAI drug in AKT versus control tumors.

The cooperative effects of CREB and FOXO3a in AKT-mediated signaling suggests that the development of small molecule inhibitors targeting AKT/CREB function while simultaneously inducing FOXO3a/Par-4 activation in CRPC tumors, represents an attractive target for drug development.

Citation Format: Jim Moselhy, Ram V. Roy, Suman Suman, Trinath P. Das, Murali Ankem, Chendil Damodaran. Identification of novel molecular targets for treatment of castration-resistant prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1951. doi:10.1158/1538-7445.AM2015-1951

Abstract 2648: A novel dual inhibitor for AKT and EGFR signaling inhibits the growth of lung cancer cells

Lung cancer is the leading cause of deaths worldwide due to cancer, of which non-small cell lung cancer is more common making up about 80 percent of lung cancer cases. Although early detection of lung cancer is feasible, targeted therapies importance are growing for advanced lung cancer. EGFR inhibitor is one of the potent options for non-small cell lung cancer (NSCLC), either alone or in combinations with chemotherapy drugs, erlotinib, gefitinib and afatinib; however the complete remission is not yet achieved. Hence, our goal is to dissect the role behind EGFR resistance in NSCLC.

Our results suggested a concomitant activation of AKT which was also evident in EGFR expressed of NSCLC. So, we hypothesized that inhibiting both AKT as well as EGFR signaling, could be a promising strategy for treatment of lung cancer. Recently we identified a small molecule, 6-dimethyl, dihydro pyranone (6ddp), that inhibits both AKT (pAKTser473) and EGFR signaling in NSCLC, which resulted growth inhibition of A549 and H460 lung cancer cell lines. Interestingly, the IC50 concentrations were at 1.5nm and 0.3nm in both the lung cancer cell lines. Inhibition of both pro-survival signaling by a small molecule, activated induction of apoptosis by up regulating caspase mediated pro-apoptotic signaling (cleaved caspase) in NSCLC cells. Interestingly, the potent molecule inhibits epithelial-mesenchymal transition (EMT) in A549 and H460 cells by modulating the kinetics of E-Cadherin, β-Catenin expression. Currently, we are planning to validate these interesting findings in animal models, which is essential to translate into clinics.

Citation Format: Arokya Mary Sashi Papu John, Murali Ankem, Chendil Damodaran. A novel dual inhibitor for AKT and EGFR signaling inhibits the growth of lung cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2648. doi:10.1158/1538-7445.AM2015-2648