An unbiased seed-based RNAi selection screen identifies small RNAs that inhibit androgen signaling and prostate cancer cell growth

Blocking androgen receptor signaling is the mainstay of therapy for advanced prostate cancer (PCa). However, acquired resistance to single agents targeting this pathway results in the development of lethal castration-resistant PCa. Combination therapy approaches represent a promising strategy for the treatment of advanced disease. Here, we explore a therapeutic strategy for PCa based on the ability of shRNAs/siRNAs to function essentially as miRNAs and, via seed sequence complementarity, induce RNA interference of numerous targets simultaneously. We developed a library that contained shRNAs with all possible seed sequence combinations to identify those ones that most potently reduce cell growth and viability when expressed in PCa cells. Validation of some of these RNAi sequences indicated that the toxic effect is associated with seed sequence complementarity to the 3' UTR of AR coregulatory and essential genes. In fact, expression of siRNAs containing the identified toxic seed sequences led to global inhibition of AR-mediated gene expression and reduced expression of cell-cycle genes. When tested in mice, the toxic shRNAs also inhibited castration-resistant PCa and exhibited therapeutic efficacy in pre-established tumors. Our findings highlight RNAi of androgen signaling networks as a promising therapeutic strategy for PCa.

Onco-condensates: formation, multi-component organization, and biological functions

Numerous cellular processes occur in the context of condensates, a type of large, membrane-less biomolecular assembly generated through phase separation. These condensates function as a hub of diversified cellular events by concentrating the required components. Cancer frequently coopts biomolecular condensation mechanisms to promote survival and/or proliferation. Onco-condensates, which refer to those that have causal roles or are critically involved in tumorigenicity, operate to abnormally elevate biological output of a proliferative process, or to suppress a tumor-suppressive pathway, thereby promoting oncogenesis. Here, we summarize advances regarding how multi-component onco-condensates are established and organized to promote oncogenesis, with those related to chromatin and transcription deregulation used as showcases. A better understanding should enable development of new means of targeting onco-condensates as potential therapeutics.

Abstract 1483: RNA interference seed-based approach to inhibit androgen signaling and induce prostate cancer cell death

The goal of this study is to identify RNA interference (RNAi) seed sequences that inhibit androgen signaling and induce toxicity in prostate cancer (PCa) cells. The high prevalence of acquired resistance to androgen deprivation therapy, as well as first and second generation androgen receptor (AR) antagonists, drives the development of lethal castration resistant prostate cancer (CRPC). As a result, PCa remains one of the leading causes of cancer related deaths in men. AR amplification, gain of function mutations and constitutively active splice isoforms of the AR, and the overexpression of AR coregulators, play considerable roles in promoting CRPC by sustaining AR activity in the presence of the low androgen environment and/or AR antagonists. The development of specific small molecule inhibitors of AR splice isoforms has been largely unsuccessful, and inhibitors of individual AR coregulators have not translated well into the clinic, likely due to their large number and functional redundancies. Therefore, novel therapeutic strategies for targeting androgen signaling in CRPC are necessary. Previous studies in our lab have demonstrated RNAi-mediated PCa cell death through seed region (nucleotides 2-8) complementarity of shRNA/siRNA guide strands to the 3’UTR of the AR and multiple AR coregulators and essential genes. In the current study, we used an unbiased novel seed-based shRNA screen to identify seed sequences that are toxic to different PCa cells, including CRPC cells expressing the clinically relevant constitutively active AR variant 7 (AR-V7). Common motifs were identified among toxic seed sequences, and the miRDB target prediction database was used to select those seeds that were predicted to target the AR and AR coregulators. Using RNA-seq analyses we confirmed that selected seed sequences inhibited global androgen signaling and identified potential direct targets known to be relevant to PCa. Conclusions: These studies have identified androgen signaling inhibitory sequences that have the potential to be used in RNAi-seed based therapies for PCa. The ability to inhibit the expression of the AR and multiple essential AR coregulators simultaneously with one agent, and the reduced likelihood of developed resistance, are considerable benefits of this approach.

Citation Format: Joshua M. Corbin, Maria J. Ruiz-Echevarria. RNA interference seed-based approach to inhibit androgen signaling and induce prostate cancer cell death [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 1483.

Seed-mediated RNA interference of androgen signaling and survival networks induces cell death in prostate cancer cells

Resistance to anti-androgen therapy in prostate cancer (PCa) is often driven by genetic and epigenetic aberrations in the androgen receptor (AR) and coregulators that maintain androgen signaling activity. We show that specific small RNAs downregulate expression of multiple essential and androgen receptor-coregulatory genes, leading to potent androgen signaling inhibition and PCa cell death. Expression of different short hairpin/small interfering RNAs (sh-/siRNAs) designed to target TMEFF2 preferentially reduce viability of PCa but not benign cells, and growth of murine xenografts. Surprisingly, this effect is independent of TMEFF2 expression. Transcriptomic and sh/siRNA seed sequence studies indicate that expression of these toxic shRNAs lead to downregulation of androgen receptor-coregulatory and essential genes through mRNA 3′ UTR sequence complementarity to the seed sequence of the toxic shRNAs. These findings reveal a form of the “death induced by survival gene elimination” mechanism in PCa cells that mainly targets AR signaling, and that we have termed androgen network death induced by survival gene elimination (AN-DISE). Our data suggest that AN-DISE may be a novel therapeutic strategy for PCa.

Abstract 3152: A tumor suppressor-regulated cell cycle derived gene signature is prognostic of recurrence risk in prostate cancer

Prostate cancer (PCa) is a complex heterogeneous disease, with the majority of cases remaining indolent and 10% of cases progressing to lethality. While some of this clinical heterogeneity can be explained by traditional clinicopathological factors, molecular profiling studies signal an extraordinary genomic variability, which may lead to diverse clinical outcomes. The identification of molecular subclasses of PCa has the potential to guide the prediction of clinical outcomes, the discovery and design of innovative prognostic biomarkers, and the development of novel therapeutics. To this end, we investigated genes associated with TMEFF2, an androgen-regulated tumor suppressor gene with exceptionally heterogeneous expression in PCa. Low levels of TMEFF2 mRNA significantly (p<0.0001) correlate with reduced disease-free survival (DFS) in patients from the Memorial Sloan Kettering Cancer Center (MSKCC) dataset. Using RNA interference, we identified a panel of 11 TMEFF2 regulated cell cycle related genes (TMCC11), with strong prognostic value. TMCC11 expression stratified radical prostatectomy (RP) patients on the risk of recurrence, served as an independent indicator of poor prognosis, and improved the prognostic value of standard clinicopathological markers in four geographically different patient cohorts (n= 834 samples). The prognostic ability of TMCC11 panel exceeded previously published oncogenic gene signatures (p=0.00017). This study provides evidence that the TMCC11 gene signature is a robust prognostic marker for PCa, reveals the value of using highly heterogeneously expressed genes, like TMEFF2, as guides to discover prognostic indicators, and suggests the possibility that low TMEFF2 expression marks a distinct subclass of PCa.

Citation Format: Joshua M. Corbin, Constantin Georgescu, Sandra Thibivilliers, Zachary Webb, Yan Zhao, Jan Koster, Kar-Ming Fung, Adam Asch, Jonathan Wren, Maria Ruiz-Echevarria. A tumor suppressor-regulated cell cycle derived gene signature is prognostic of recurrence risk in prostate 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 3152.

The TMEFF2 tumor suppressor modulates integrin expression, RhoA activation and migration of prostate cancer cells

Cell adhesion and migration play important roles in physiological and pathological states, including embryonic development and cancer invasion and metastasis. The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) is expressed mainly in brain and prostate and its expression is deregulated in prostate cancer. We have previously shown that TMEFF2 can function as a tumor suppressor by inhibiting cell migration and invasion of prostate cells. However, the molecular mechanisms involved in this inhibition are not clear. In this study we demonstrate that TMEFF2 affects cell adhesion and migration of prostate cancer cells and that this effect correlates with changes in integrin expression and RhoA activation. Deletion of a 13 basic-rich amino acid region in the cytoplasmic domain of TMEFF2 prevented these effects. Overexpression of TMEFF2 reduced cell attachment and migration on vitronectin and caused a concomitant decrease in RhoA activation, stress fiber formation and expression of αv, β1 and β3 integrin subunits. Conversely, TMEFF2 interference in 22Rv1 prostate cancer cells resulted in an increased integrin expression. Results obtained with a double TRAMP/TMEFF2 transgenic mouse also indicated that TMEFF2 expression reduced integrin expression in the mouse prostate. In summary, the data presented here indicate an important role of TMEFF2 in regulating cell adhesion and migration that involves integrin signaling and is mediated by its cytoplasmic domain.

Biological response to variation of acid-volatile sulfides and metals in field-exposed spiked sediments

Vertical and temporal variations of acid-volatile sulfides (AVS) and simultaneously extracted metals (SEM) in sediment can control biological impacts of metals. To assess the significance of these variations in field sediments, sediments spiked with cadmium, copper, lead, nickel, and zinc were deployed in Narragansett Bay for four months and recolonization by benthic organisms investigated. In surface sediments, concentrations of AVS decreased with time whenever AVS exceeded SEM but remained unchanged when AVS was less than SEM; in subsurface sediments, concentrations increased slightly. Concentrations of total SEM decreased with time only in surface sediments in which SEM exceeded AVS. Metals were not detected in interstitial waters of sediments where AVS exceeded SEM but were significant when SEM exceeded AVS and followed the order of solubilities of their sulfides. Concentrations in interstitial waters decreased with time, but exceeded U.S. Environmental Protection Agency chronic water quality criteria for 56 to 119 d. After 119 d, faunal assemblages in all treatments were similar to controls. Lack of biological response was related to vertical distributions of AVS and SEM. Biological exposure took place in near-surface sediments, where AVS exceeded SEM in even the highest treatments. Therefore, concentrations of metals in interstitial waters were low and consequently biological impacts were undetectable.

The Corbin and Strauss Chronic Illness Trajectory model: an update

As the nature of the American health care system, chronic illness, and nursing change, theoretical models used to guide nursing management of chronic conditions must be updated to keep abreast of these changes, while still retaining their core concepts. This article offers a revised version of the Corbin and Strauss Chronic Illness Trajectory Framework. The most notable changes include a greater emphasis on health promotion and illness prevention, streamlined language to make it more user friendly, and increased focus on the global influences on health care. The nurse also takes a more prominent position in management of such conditions, because only nurses, among health care workers, have the wide based education, training, focus on health promotion, technological expertise, and holistic approach to health care necessary to address the wide range issues and problems of chronic management, which will continue to grow as we move into the 21st Century.

A nursing model for chronic illness management based upon the Trajectory Framework

The trajectory framework developed by Strauss and associates provides a conceptual basis for developing a nursing model that gives direction for practice, teaching, and research in the area of chronic illness. This paper presents an overview of the trajectory framework and shows how it can be used to generate such a nursing model.