Abstract Background: Castration-resistant prostate cancer (CRPC) is an incurable disease and a leading cause of cancer death in men worldwide. Olaparib (Lynparza) was among the first PARP inhibitors (PARPi) approved for the treatment of CRPC tumors harboring DNA repair defects. However, clinical resistance to PARPi’s has been documented. The mechanisms underlying resistance to PARPi’s remain elusive. To study acquired resistance, we developed olaparib-resistant LN-OlapR and 2B-OlapR cell lines generated through chronic olaparib treatment of the olaparib-sensitive cell lines LNCaP and C4-2B, respectively. RNA-seq revealed IGFBP3 is overexpressed in both OlapR cell lines. IGFBP3 overexpression is correlated with poor clinical outcome and is thought to participate in DNA repair pathways. IGFBP3 plays a key role in nonhomologous end joining (NHEJ) repair through a ternary complex with EGFR and DNA-PKcs. The IGFBP3/EGFR signaling axis is thought to modulate NHEJ repair and could have implications for PARPi sensitivity. We hypothesize that increased IGFBP3 expression promotes PARPi resistance by enhancing DNA repair capacity. Methods: RNA-sequencing and gene set enrichment analysis were used to determine the expression profile changes in resistant cells compared to parental cells. Real time PCR and western blots confirmed the expression of DNA damage repair genes such as γH2AX, EGFR, and DNA-PKcs. ELISA was used to determine IGFBP3 secretion. RNAi was used to inhibit IGFBP3 and EGFR expression. Gefitinib was used to inhibit EGFR activity. Cell viability assays were used to assess cell growth. Results: Transcriptomic profiling revealed that IGFBP3 is highly expressed in resistant models. We verified increased levels of IGFBP3 RNA and protein in both OlapR models. We found that RNAi inhibition of IGFBP3 increases γH2AX and cleaved-PARP protein levels in the resistant models, which suggests accumulation of DNA double strand breaks (DSBs) leading to genomic instability and cell death. We discovered increased phosphorylation of EGFR and DNA-PKcs in the resistant cells. Furthermore, silencing/inhibiting IGFBP3 and EGFR reduces OlapR cell viability and resensitizes resistant cells to treatment. Conclusions: Our findings demonstrated that inhibiting IGFBP3 and EGFR aids in PARPi sensitivity in the resistant setting. Future work will utilize OlapR models to study how the IGFBP3/EGFR/DNA-PKcs protein complex promotes the development of resistance. Understanding the role of IGFBP3 in PARPi resistance will enhance our ability to re-sensitize resistant CRPC to PARPi therapeutics. Citation Format: Amy R. Leslie, Shu Ning, Leandro S. D'Abronzo, Cameron Armstrong, Masuda Sharifi, Zachary A. Schaaf, Wei Lou, Christopher P. Evans, Hong-Wu Chen, Alan Lombard, Allen C. Gao. IGFBP3 promotes resistance to olaparib via modulating EGFR signaling in advanced prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3862.
<div>Abstract<p>The next-generation antiandrogen drugs such as enzalutamide and abiraterone extend survival times and improve quality of life in patients with advanced prostate cancer. However, resistance to both drugs occurs frequently through mechanisms that are incompletely understood. Wnt signaling, particularly through Wnt5a, plays vital roles in promoting prostate cancer progression and induction of resistance to enzalutamide and abiraterone. Development of novel strategies targeting Wnt5a to overcome resistance is an urgent need. In this study, we demonstrated that Wnt5a/FZD2-mediated noncanonical Wnt pathway is overexpressed in enzalutamide-resistant prostate cancer. In patient databases, both the levels of Wnt5a and FZD2 expression are upregulated upon the development of enzalutamide resistance and correlate with higher Gleason score, biochemical recurrence, and metastatic status, and with shortened disease-free survival duration. Blocking Wnt5a/FZD2 signal transduction not only diminished the activation of noncanonical Wnt signaling pathway, but also suppressed the constitutively activated androgen receptor (AR) and AR variants. Furthermore, we developed a novel bioengineered BERA-Wnt5a siRNA construct and demonstrated that inhibition of Wnt5a expression by the BERA-Wnt5a siRNA significantly suppressed tumor growth and enhanced enzalutamide treatment <i>in vivo</i>. These results indicate that Wnt5a/FZD2 signal pathway plays a critical role in promoting enzalutamide resistance, and targeting this pathway by BERA-Wnt5a siRNA can be developed as a potential therapy to treat advanced prostate cancer.</p></div>
Supplementary Data from Bioengineered BERA-Wnt5a siRNA Targeting Wnt5a/FZD2 Signaling Suppresses Advanced Prostate Cancer Tumor Growth and Enhances Enzalutamide Treatment
The delta smelt (Hypomesus transpacificus) is a pelagic fish species listed as endangered under both the USA Federal and Californian State Endangered Species Acts and considered an indicator of ecosystem health in its habitat range, which is limited to the Sacramento-San Joaquin estuary in California, USA. Anthropogenic contaminants are one of multiple stressors affecting this system, and among them, current-use insecticides are of major concern. Interrogative tools are required to successfully monitor effects of contaminants on the delta smelt, and to research potential causes of population decline in this species. We have created a microarray to investigate genome-wide effects of potentially causative stressors, and applied this tool to assess effects of the pyrethroid insecticide esfenvalerate on larval delta smelt. Selected genes were further investigated as molecular biomarkers using quantitative PCR analyses.Exposure to esfenvalerate affected swimming behavior of larval delta smelt at concentrations as low as 0.0625 mug.L-1, and significant differences in expression were measured in genes involved in neuromuscular activity. Alterations in the expression of genes associated with immune responses, along with apoptosis, redox, osmotic stress, detoxification, and growth and development appear to have been invoked by esfenvalerate exposure. Swimming impairment correlated significantly with expression of aspartoacylase (ASPA), an enzyme involved in brain cell function and associated with numerous human diseases. Selected genes were investigated for their use as molecular biomarkers, and strong links were determined between measured downregulation in ASPA and observed behavioral responses in fish exposed to environmentally relevant pyrethroid concentrations.The results of this study show that microarray technology is a useful approach in screening for, and generation of molecular biomarkers in endangered, non-model organisms, identifying specific genes that can be directly linked with sublethal toxicological endpoints; such as changes in expression levels of neuromuscular genes resulting in measurable swimming impairments. The developed microarrays were successfully applied on larval fish exposed to esfenvalerate, a known contaminant of the Sacramento-San Joaquin estuary, and has permitted the identification of specific biomarkers which could provide insight into the factors contributing to delta smelt population decline.
Abstract The standard of care for patients with recurrent prostate cancer (PCa) is the use of androgen receptor (AR) antagonists, but the treatment ultimately fails, resulting in the development of castration resistant PCa (CRPC). Patients with CRPC are frequently continue to express an active AR, despite castration resistance, and AR inhibitors remain effective in these patients for several months. We previously showed that upregulation of mammalian target of rapamycin (mTOR) activity upon use of AR antagonists contributed to acquired resistance to this therapy, and that a combination of an mTOR inhibitor and an AR antagonist overcame resistance to AR antagonists alone (Wang et al, Oncogene, 2008;27(56):7106-17). Based on our data, a Phase II clinical trial was conducted to determine the efficacy of the combination of the mTOR inhibitor RAD001 and the AR antagonist bicalutamide in bicalutamide-naïve CRPC patients (ClinicalTrials.gov: NCT00814788). This study, which was recently concluded, showed a response rate of 75% with this combination with the historical control of 25%. The overall goal of this project was to define pathways that results in resistance to combinations of mTOR and AR inhibitors in patients with CRPC. Comparison of various mTOR inhibitors: the mTORC1 inhibitor RAD001, a mTORC1/C2 dual inhibitor INK128 and a mTORC1/C2/PI3K triple inhibitor BEZ-235 either alone or in combination with AR antagonists bicalutamide and enzalutamide in various prostate derived cell lines including C4-2, PC-346C, 22Rv1 and CWR-R1, identified cells that were resistant (CWR-R1, PC-346C) vs those that were sensitive (22Rv1, C4-2) to these inhibitors. Investigation of the base-line molecular profile of these cells demonstrated that those that expressed high levels of phosphorylated form of eIF4E (S209) were resistant to mTOR inhibitors. Downregulation of eIF4E phosphorylation by siRNA resulted in sensitivity of CRPC cells to the combination of the mTOR inhibitors with AR antagonists. Investigation of the mechanism by which eIF4E phosphorylation levels increased in certain CRPC cells but not in others revealed that expression and transcriptional activity of the AR negatively correlated with the levels of eIF4E phosphorylation. In cells with high basal levels of phospho-eIF4E, bicalutamide further increased eIF4E phosphorylation, whereas those with low eIF4E levels were not further affected. The ability of AR inhibition to suppress eIF4E phosphorylation was mediated by MAP kinase interacting kinase (Mnk), and the ability of some cells to phosphorylate eIF4E, but not others, correlated with the levels of Mnk phosphorylation. Based on these studies, we predict that patients with high basal PSA who express low levels of Mnk phosphorylation are the ones who are likely to respond to the combination of an mTOR inhibitor and an AR antagonist. Citation Format: Leandro S. D’Abronzo, Michael Crapuchettes, Ryan E. Beggs, Swagata Bose, Salma Siddiqui, Yu Wang, Blythe Durbin-Johnson, Chong-Xian Pan, Paramita Ghosh. Increased phosphorylation of eIF4E induces resistance to treatment with mTOR inhibitors alone or together with AR antagonists in advanced prostate cancer. [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 236.
Despite overexpression of the ErbB (EGFR/HER2/ErbB3/ErbB4) family in castration-resistant prostate cancer (CRPC), some inhibitors of this family, including the dual EGFR/HER2 inhibitor lapatinib, failed in Phase II clinical trials. Hence, we investigated mechanisms of lapatinib resistance to determine whether alternate ErbB inhibitors can succeed. The CWR22 human tumour xenograft and its CRPC subline 22Rv1 and sera from lapatinib-treated CRPC patients from a previously reported Phase II trial were used to study lapatinib resistance. Mechanistic studies were conducted in LNCaP, C4-2 and 22Rv1 cell lines. Lapatinib increased intratumoral HER2 protein, which encouraged resistance to this treatment in mouse models. Sera from CRPC patients following lapatinib treatment demonstrated increased HER2 levels. Investigation of the mechanism of lapatinib-induced HER2 increase revealed that lapatinib promotes HER2 protein stability, leading to membrane localisation, EGFR/HER2 heterodimerisation and signalling, elevating cell viability. Knockdown of HER2 and ErbB3, but not EGFR, sensitised CRPC cells to lapatinib. At equimolar concentrations, the recently FDA-approved pan-ErbB inhibitor dacomitinib decreased HER2 protein stability, prevented ErbB membrane localisation (despite continued membrane integrity) and EGFR/HER2 heterodimerisation, thereby decreasing downstream signalling and increasing apoptosis. Targeting the EGFR axis using the irreversible pan-ErbB inhibitor dacomitinib is a viable therapeutic option for CRPC.
Prostate cancer (PCa) is initially regulated by the androgen receptor (AR), a ligand-activated, transcription factor (hormone-sensitive PCa (HSPC)), but eventually become androgen-refractory or castration-resistant (CRPC) because of mechanisms that bypass the AR, including ErbB3, a member of the epidermal growth factor receptor (EGFR) family. ErbB3 is synthesized in the cytoplasm and transported to the plasma membrane for ligand binding and dimerization, where it regulates downstream signaling, but nuclear forms are reported. Here, we demonstrate in prostatectomy samples that ErbB3 nuclear localization is observed in malignant, but not benign prostate. and that cytoplasmic (but not nuclear) ErbB3 correlated positively with AR expression but negatively with AR transcriptional activity. In support of the latter, androgen depletion upregulated cytoplasmic, but not nuclear ErbB3, while in vivo studies showed that castration suppressed ErbB3 nuclear localization in HSPC, but not CRPC tumors. In vitro treatment with the ErbB3 ligand heregulin-1β (HRG) induced ErbB3 nuclear localization, which was androgen-regulated in HSPC but not in CRPC. In turn, HRG upregulated AR transcriptional activity in CRPC but not in HSPC cells. Positive correlation between ErbB3 and AR expression was demonstrated in AR-null PC-3 cells where stable transfection of AR restored HRG-induced ErbB3 nuclear transport, while AR knockdown in LNCaP reduced cytoplasmic ErbB3. Mutations of ErbB3's kinase domain did not affect its localization but was responsible for cell viability in CRPC cells. Taken together, we conclude that AR expression regulated ErbB3 expression, its transcriptional activity suppressed ErbB3 nuclear translocation, and HRG binding to ErbB3 promoted it.
<div>Abstract<p>The mechanisms resulting in resistance to next-generation antiandrogens in castration-resistant prostate cancer are incompletely understood. Numerous studies have determined that constitutively active androgen receptor (AR) signaling or full-length AR bypass mechanisms may contribute to the resistance. Previous studies established that AKR1C3 and AR-V7 play important roles in enzalutamide and abiraterone resistance. In the present study, we found that AKR1C3 increases AR-V7 expression in resistant prostate cancer cells through enhancing protein stability via activation of the ubiquitin-mediated proteasome pathway. AKR1C3 reprograms AR signaling in enzalutamide-resistant prostate cancer cells. In addition, bioinformatical analysis of indomethacin-treated resistant cells revealed that indomethacin significantly activates the unfolded protein response, p53, and apoptosis pathways, and suppresses cell-cycle, Myc, and AR/ARV7 pathways. Targeting AKR1C3 with indomethacin significantly decreases AR/AR-V7 protein expression <i>in vitro</i> and <i>in vivo</i> through activation of the ubiquitin-mediated proteasome pathway. Our results suggest that the AKR1C3/AR-V7 complex collaboratively confers resistance to AR-targeted therapies in advanced prostate cancer.</p></div>
The health condition of out-migrating juvenile salmonids can influence migration success. Physical damage, pathogenic infection, contaminant exposure, and immune system status can affect survival probability. The present study is part of a wider investigation of out-migration success in juvenile steelhead (Oncorhynchus mykiss) and focuses on the application of molecular profiling to assess sublethal effects of environmental stressors in field-collected fish. We used a suite of genes in O. mykiss to specifically assess responses that could be directly related to steelhead health condition during out-migration. These biomarkers were used on juvenile steelhead captured in the Snake River, a tributary of the Columbia River, in Washington, USA, and were applied on gill and anterior head kidney tissue to assess immune system responses, pathogen-defense (NRAMP, Mx, CXC), general stress (HSP70), metal-binding (metallothionein-A), and xenobiotic metabolism (Cyp1a1) utilizing quantitative polymerase chain reaction (PCR) technology. Upon capture, fish were ranked according to visual external physical conditions into good, fair, poor, and bad categories; gills and kidney tissues were then dissected and preserved for gene analyses. Transcription responses were tissue-specific for gill and anterior head kidney with less significant responses in gill tissue than in kidney. Significant differences between the condition ranks were attributed to NRAMP, MX, CXC, and Cyp1a1 responses. Gene profiling correlated gene expression with pathogen presence, and results indicated that gene profiling can be a useful tool for identifying specific pathogen types responsible for disease. Principal component analysis (PCA) further correlated these responses with specific health condition categories, strongly differentiating good, poor, and bad condition ranks. We conclude that molecular profiling is an informative and useful tool that could be applied to indicate and monitor numerous population-level parameters of management interest.
