Impact of high-stakes exams, incentives, and preparation on student performance: Insights from the pharmacy curriculum outcomes assessment

INTRODUCTION

Efforts to ensure success of pharmacy students in passing pharmacy standardized exams require substantial investments. Engaging students effectively can be a challenge when there are no consequences for non-participation or poor performance. This study examined how engagement reinforcement, including high-stake exam requirements, instructional strategies, and incentives, impacted student performance on the Pharmacy Curriculum Outcomes Assessment (PCOA).

METHODS

PCOA scores, milestone exams, grade point averages (GPAs), and PCOA preparedness assessments for cohorts (Co) that received high-stakes exams, incentives, and preparation (Co2019, Co2020, and Co2021) was compared with those that did not receive these interventions (Co2017 and Co2018). Students' perceptions regarding reinforcement, incentive, and preparedness were evaluated using an anonymous survey.

RESULTS

Analyzing data from 545 students over five years, mandated PCOA preparedness, high-stakes PCOA requirements, and incentives for Co2019, Co2020, and Co2021 improved scores by 11% to 18% compared to Co2017 and Co2018. This corresponded to a rise in performance from the 12th to 27th percentile for Co2017 and Co2018 to the 39th to 49th percentile for Co2019, Co2020, and Co2021. In these later cohorts, PCOA scores consistently correlated with the school's milestone exams and students' cumulative GPAs (correlation coefficients 0.47-0.70, P < .001), while no such correlation was observed in Co2017 and Co2018. Faculty-led PCOA preparation yielded better results (48.2% in Co2020, 45.8% in Co2021) than self-learning (42% in Co2019). Students using faculty-prepared assessments reported increased confidence in biomedical and pharmaceutical sciences.

CONCLUSIONS

This study highlights the importance of high-stakes requirements, incentives, and thorough preparation in improving PCOA results.

A pharmacist-led community-based survey study: Determining the impact of the Covid-19 pandemic on actionable factors associated with worse cancer outcomes and cancer health disparities

Purpose

The goals of this cross-sectional community-based survey study were to assess the impact of the Covid-19 pandemic on actionable factors which are known to contribute to worse cancer outcomes, and to determine whether race and ethnicity-based differences exist.

Methods

A survey study which captured demographic information and changes in cancer outcomes-related factors since the start of the Covid-19 pandemic, was conducted at a public Covid-19 vaccination clinic over a period of 10 days during March 2021. Surveys were administered in multiple languages. Chi-square tests and ANOVA followed by post-hoc Dunnett testing assessed for race and ethnicity-based differences.

Results

A total of 949 people participated (61.6% participation rate). Ninety-three surveys were removed based on inclusion criteria giving a final participant number of 856. Many participants reported postponing cancer screenings (17.8%) and cancellation of medical appointments (22.8% and 25.8% reported cancelled appointments by providers or themselves, respectively) due to the pandemic. Participants also reported decreased physical activity (44.7%) and increased tobacco and/or marijuana usage (7.0%). Conversely, participants reported consuming more fruits and vegetables (21.4%) and decreasing alcohol consumption (21.4%). Several race-related differences but no ethnicity-related differences were observed.

Conclusion

Our data can be used to help guide pharmacist-led targeted outreach in our community which will help mitigate Covid-19 pandemic-driven changes in behaviors associated with worse cancer outcomes and exacerbation of cancer health disparities. To our knowledge, this is the first cancer outcomes-related study to be conducted at a public Covid-19 vaccination site and is the first pharmacist-led study in this area.

Effectiveness of an Advanced Naloxone Training, Simulation, and Assessment of Second-Year Pharmacy Students

Background: Opioid overdoses continue to be one of the most urgent public health priorities. In 2020, reported overdose deaths in the United States reached a high of over 93,000 cases. As the COVID-19 pandemic and opioid crisis continues to be addressed, life-saving agents must be more widely accessible to those with a high overdose risk. An essential step to increasing access is to train student pharmacists to dispense naloxone. Once licensed, the number of personnel authorized to dispense naloxone can increase. Objectives: To design a training program to educate second-year pharmacy (P2) students on furnishing naloxone under a state protocol. Methods: A multi-phased curriculum-based naloxone training program was delivered to P2 students and included lecture-based education, team-based learning (TBL) applications, case-based scenarios, and summative assessments to improve student knowledge and confidence in furnishing naloxone. Students were surveyed on their knowledge and confidence with naloxone prior to training, after the in-class training and TBL applications and after three assessments. Assessments included simulated patient counseling, case-based scenarios, and proper dispensing of naloxone in a community pharmacy simulation lab. Results: A total of 185 student pharmacists completed the naloxone training program and 68 completed all three surveys. Average scores for naloxone assessments were 83% for the APPS lab patient case, 90.5% for the prescription label typed for the naloxone product, and 88.5% for patient counseling. Statistically significant increases in knowledge-based quiz-like scores (42.1% after training vs. 7.2% after assessment) and in the proportion of students affirmatively answering survey questions after training and assessment was observed. Conclusion: Multi-phase curriculum-based naloxone training program improved pharmacy student knowledge and confidence in furnishing naloxone under a state BOP protocol.

COVID-19-Driven Improvements and Innovations in Pharmacy Education: A Scoping Review

The COVID-19 pandemic led to many colleges of pharmacy having to make major changes relating to their infrastructure and delivery of their curriculum within a very short time frame, including the transition of many components to an online setting. This scoping review sought to summarize what is known about the impact of COVID-19 on pharmacy education and the effectiveness of adaptation strategies which were put in place. PubMed, Web of Science, OVID Medline, and MedEdPortal were searched to identify pharmacy education-related articles published since the beginning of the COVID-19 pandemic. For article inclusion, the following criteria had to be met: described original research, related directly to PharmD or PharmBS education, related to the impact of COVID-19 on pharmacy education, and was available in English. Out of a total of 813 articles, 50 primary research articles were selected for inclusion. Our review of these identified four domains relating to the impact of COVID-19 on pharmacy education and/or effectiveness of adaptation strategies: (1) lab-based courses and activities (including interprofessional education activities), (2) experiential education, (3) didactic education, and (4) student well-being. The key research findings are summarized and discussed. While the COVID-19 pandemic has clearly brought many challenges to pharmacy education, it has also led to key improvements and innovations.

Use of Concept Mapping to Identify Expectations of Pharmacy Students Selecting Elective Courses

The objective of this study was to demonstrate the use of concept mapping as a method for analyzing pharmacy students’ qualitative perceptions of their expectations of elective courses and to thus help guide delivery methods and course content. A survey containing demographic, Likert scale, and open-ended questions was administered to second-year pharmacy students prior to the start of elective courses and an innovative methodology, concept mapping, was used to identify major themes relating to student expectations. The association between preferred class delivery method (online versus in person) with student gender and English-as-a-second-language status (ESL) was also assessed. Note that this study was conducted prior to the COVID-19 pandemic. Ninety-eight out of 133 students (74%) completed the survey. Overall, 56% students stated that they preferred online delivery of courses (68% of these students were female, 36% were male). ESL status did not impact preference. The most common themes relating to student course expectations were the desire to learn about the elective course topic as well “real-world” utility. Our combined data indicate that delivery method is a key factor contributing to students’ choice of elective course and that concept mapping is an effective and efficient way to help identify student expectations of elective courses.

Use of End-of-Class Quizzes to Promote Pharmacy Student Self-Reflection, Motivate Students to Improve Study Habits, and to Improve Performance on Summative Examinations

Underperforming students are often unaware of deficiencies requiring improvement until after poor performance on summative exams. The goal of the current study was to determine whether inclusion of individual end-of-class formative quizzes, which comprise of higher level Bloom's questions, could encourage students to reflect on and address deficiencies and improve academic performance. Ninety-seven out of 123 first-year pharmacy students (79%) enrolled in a Biochemistry and Cell & Molecular Biology course participated in a single-blinded, randomized, controlled, crossover study. Paired t-test analyses demonstrated that that implementation of individual end-of-class formative quizzes resulted in significantly higher summative exam scores for below average students (p = 0.029). Notably, inclusion of quizzes significantly improved performance on higher Bloom's questions for these students (p = 0.006). Analysis of surveys completed by students prior to summative exam indicate that the formative end-of-class quizzes helped students identify deficiencies (89%) and making them feel compelled to study more (83%) and attend review sessions (61%). Many students indicated that quizzes increased stress levels (45%). Our collective data indicate that quizzes can improve summative exam performance for below average first year pharmacy students, and improve self-reflection and student motivation to study. However, the impact on student stress levels should be considered.

Abstract B083: Dysregulation of the AR-Nrdp1-ErbB3 axis occurs in African American prostate cancer patients and is associated with worse outcomes

Background: We previously showed that Nrdp1, an E3 ubiquitin ligase, is transcriptionally regulated by the androgen receptor (AR) in prostate cancer (CaP) cells and that Nrdp1 can post-translationally regulate ErbB3 (an EGFR family member) levels via ubiquitination and subsequent proteasomal degradation. Increased levels of ErbB3 are associated with worse CaP patient outcome. The goal of the current study was to determine whether dysregulation of the AR-Nrdp1-ErbB3 axis contributes to prostate cancer health disparities for African American (AA) men, and to identify the underlying mechanisms involved. Methods: Expression levels and localization of AR, Nrdp1, and ErbB3 were assessed in a total of 208 CaP patient samples (50 African American (AA) and 158 Caucasian (CA) CaP patients) and two cell lines (LNCaP (CA) and MDAPCa2b (AA)). Expression levels and localization of these molecules were determined by immunohistochemistry (IHC) and subcellular fractionation and western blot. A combination of knockdown (siRNA), forced overexpression (Nrdp1-FLAG construct), and treatment with enzalutamide or synthetic androgen (R1881) experiments were employed to investigate the relationship between AR, Nrdp1, and ErbB3 expression levels and localization and to identify differences in AA and CA cell lines. Immunoprecipitation allowed for investigation of the mechanisms which facilitate nuclear transport of Nrdp1. Results: A statistically significant negative association between cytoplasmic levels of AR (AR C) and nuclear Nrdp1 (Nrdp1 N) exists in both Caucasian (CA) and African American (AA) prostate cancer (CaP) patients, but this association was stronger in AA patients compared to CA patients (Spearman correlation coefficient of -0.62 for AA patients, and -0.36 for CA patients). Increased nuclear Nrdp1 expression levels were associated with increased 5-year survival rates, and reduced nuclear Nrdp1 expression levels predicted biochemical recurrence (AUC 0.63). Dysregulation of the AR-Nrdp1-ErbB3 axis in AA CaP cells was also observed in cell line studies; AA CaP cells expressed significantly lower levels of both total and nuclear Nrdp1 compared to their CA CaP counterparts. Manipulation of AR expression levels and localization via knockdown and inhibition with enzalutamide had a lesser impact on Nrdp1 expression levels and localization in AA versus CA CaP cells. Immunoprecipitation studies demonstrated that Nrdp1 can bind to AR in CA CaP cells but not AA CaP cells. Conclusions: Our combined data indicate that dysregulation of the AR-Nrdp1-ErbB3 axis occurs to a larger extent in AA than CA CaP cells and that this can contribute to worse patient outcomes. Our data also indicate that lack of binding between AR and Nrdp1 in AA CaP cells may account for the lower levels of nuclear Nrdp1 observed in AA CaP cells. Further understanding of the mechanisms which regulate Nrdp1 levels and localization may allow for the development of treatments which help abrogate cancer health disparities.

Citation Format: Anhao Sam, Shawna Evans, Elizabeth Browning, Sheryl Krig, Neelu Batra, Thomas Steele, Salma Siddqui, Paramita Ghosh, Ruth Vinall. Dysregulation of the AR-Nrdp1-ErbB3 axis occurs in African American prostate cancer patients and is associated with worse outcomes [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B083.

Abstract B084: Dysregulation of the AR-Nrdp1-ErbB3 axis occurs in African American prostate cancer patients and is associated with worse outcomes

Background: We previously showed that Nrdp1, an E3 ubiquitin ligase, is transcriptionally regulated by the androgen receptor (AR) in prostate cancer (CaP) cells and that Nrdp1 can post-translationally regulate ErbB3 (an EGFR family member) levels via ubiquitination and subsequent proteasomal degradation. Increased levels of ErbB3 are associated with worse CaP patient outcome. The goal of the current study was to determine whether dysregulation of the AR-Nrdp1-ErbB3 axis contributes to prostate cancer health disparities for African American (AA) men, and to identify the underlying mechanisms involved. Methods: Expression levels and localization of AR, Nrdp1, and ErbB3 were assessed in a total of 208 CaP patient samples (50 African American (AA) and 158 Caucasian (CA) CaP patients) and two cell lines (LNCaP (CA) and MDAPCa2b (AA)). Expression levels and localization of these molecules were determined by immunohistochemistry (IHC) and subcellular fractionation and western blot. A combination of knockdown (siRNA), forced overexpression (Nrdp1-FLAG construct), and treatment with enzalutamide or synthetic androgen (R1881) experiments were employed to investigate the relationship between AR, Nrdp1, and ErbB3 expression levels and localization and to identify differences in AA and CA cell lines. Immunoprecipitation allowed for investigation of the mechanisms which facilitate nuclear transport of Nrdp1. Results: A statistically significant negative association between cytoplasmic levels of AR (AR C) and nuclear Nrdp1 (Nrdp1 N) exists in both Caucasian (CA) and African American (AA) prostate cancer (CaP) patients, but this association was stronger in AA patients compared to CA patients (Spearman correlation coefficient of -0.62 for AA patients, and -0.36 for CA patients). Increased nuclear Nrdp1 expression levels were associated with increased 5-year survival rates, and reduced nuclear Nrdp1 expression levels predicted biochemical recurrence (AUC 0.63). Dysregulation of the AR-Nrdp1-ErbB3 axis in AA CaP cells was also observed in cell line studies; AA CaP cells expressed significantly lower levels of both total and nuclear Nrdp1 compared to their CA CaP counterparts. Manipulation of AR expression levels and localization via knockdown and inhibition with enzalutamide had a lesser impact on Nrdp1 expression levels and localization in AA versus CA CaP cells. Immunoprecipitation studies demonstrated that Nrdp1 can bind to AR in CA CaP cells but not AA CaP cells. Conclusions: Our combined data indicate that dysregulation of the AR-Nrdp1-ErbB3 axis occurs to a larger extent in AA than CA CaP cells and that this can contribute to worse patient outcomes. Our data also indicate that lack of binding between AR and Nrdp1 in AA CaP cells may account for the lower levels of nuclear Nrdp1 observed in AA CaP cells. Further understanding of the mechanisms which regulate Nrdp1 levels and localization may allow for the development of treatments which help abrogate cancer health disparities.

Note: This abstract was not presented at the conference.

Citation Format: Anhao Sam, Elizabeth Browning, Shawna Evans, Thomas Steele, Paramita Ghosh, Ruth Vinall. Dysregulation of the AR-Nrdp1-ErbB3 axis occurs in African American prostate cancer patients and is associated with worse outcomes [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B084.

XPO1 inhibition by selinexor induces potent cytotoxicity against high grade bladder malignancies

Treatment options for high grade urothelial cancers are limited and have remained largely unchanged for several decades. Selinexor (KPT-330), a first in class small molecule that inhibits the nuclear export protein XPO1, has shown efficacy as a single agent treatment for numerous different malignancies, but its efficacy in limiting bladder malignancies has not been tested. In this study we assessed selinexor-dependent cytotoxicity in several bladder tumor cells and report that selinexor effectively reduced XPO1 expression and limited cell viability in a dose dependent manner. The decrease in cell viability was due to an induction of apoptosis and cell cycle arrest. These results were recapitulated in in vivo studies where selinexor decreased tumor growth. Tumors treated with selinexor expressed lower levels of XPO1, cyclin A, cyclin B, and CDK2 and increased levels of RB and CDK inhibitor p27, a result that is consistent with growth arrest. Cells expressing wildtype RB, a potent tumor suppressor that promotes growth arrest and apoptosis, were most susceptible to selinexor. Cell fractionation and immunofluorescence studies showed that selinexor treatment increased nuclear RB levels and mechanistic studies revealed that RB ablation curtailed the response to the drug. Conversely, limiting CDK4/6 dependent RB phosphorylation by palbociclib was additive with selinexor in reducing bladder tumor cell viability, confirming that RB activity has a role in the response to XPO1 inhibition. These results provide a rationale for XPO1 inhibition as a novel strategy for the treatment of bladder malignancies.

Abstract B22: Increased phosphorylation of eIF4E induces resistance to treatment with mTOR inhibitors together with AR antagonists in advanced prostate cancer

The anti-androgen bicalutamide is widely used in the treatment of advanced prostate cancer (CaP) in many countries, but its effect on castration resistant CaP (CRPC) is limited. We previously showed that resistance to bicalutamide results from increased activation of the mechanistic target of rapamycin (mTOR); indicating a role for mTOR inhibitors in CaP treatment. Interestingly, a clinical trial testing combinations of the mTOR inhibitor RAD001 with bicalutamide were initially effective (PSA decline&gt;50%) in 62.5% CRPC patients, but many initial responders later developed resistance. Here we investigate causes for their difference in response. Evaluation of various CRPC cell lines identified resistant vs sensitive in vitro models, and revealed that increased eIF4E phosphorylation at S209 is associated with resistance to the combination. To recognize potential causes of resistance, we demonstrated using a human tumor xenograft mouse model, that bicalutamide use is associated with an increase in eIF4E(S209) phosphorylation. Investigations revealed that AR suppressed eIF4E phosphorylation, while the use of anti-androgens relieved this suppression, thereby triggering its increase. Additional investigation on the consequences of increased eIF4E phosphorylation in human prostatectomy samples revealed that increased eIF4E phosphorylation strongly correlated with the cell proliferation marker Ki67, indicating a role for eIF4E in tumor growth. Inhibition of eIF4E phosphorylation by siRNA suppression or treatment with CGP57380 (an inhibitor of MAPK interacting serine-threonine kinases Mnk1/2, the eIF4E upstream kinase,) sensitized CRPC cells to RAD001+bicalutamide, while eIF4E overexpression induced resistance. Our results demonstrate that bicalutamide treatment induced an increase in eIF4E phosphorylation by inhibition of AR which otherwise suppressed this phosphorylation. Increased eIF4E phosphorylation then induced resistance to the combination of anti-androgens with mTOR inhibitors by increasing proliferation. These results also indicate that resistance to RAD001+bicalutamide can be prevented by the concurrent use of a Mnk1/2 inhibitor.

Citation Format: Leandro S. D'Abronzo, Michael Crapuchettes, Ryan Beggs, Ruth Vinall, Clifford Tepper, Salma Siddiqui, Maria Mudryj, Frank Melgoza, Blythe Durbin-Johnson, Ralph deVere White, Paramita Ghosh. Increased phosphorylation of eIF4E induces resistance to treatment with mTOR inhibitors together with AR antagonists in advanced prostate cancer. [abstract]. In: Proceedings of the AACR Special Conference on Translational Control of Cancer: A New Frontier in Cancer Biology and Therapy; 2016 Oct 27-30; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2017;77(6 Suppl):Abstract nr B22.

Molecular Dissection of Induced Platinum Resistance through Functional and Gene Expression Analysis in a Cell Culture Model of Bladder Cancer

We report herein the development, functional and molecular characterization of an isogenic, paired bladder cancer cell culture model system for studying platinum drug resistance. The 5637 human bladder cancer cell line was cultured over ten months with stepwise increases in oxaliplatin concentration to generate a drug resistant 5637R sub cell line. The MTT assay was used to measure the cytotoxicity of several bladder cancer drugs. Liquid scintillation counting allowed quantification of cellular drug uptake and efflux of radiolabeled oxaliplatin and carboplatin. The impact of intracellular drug inactivation was assessed by chemical modulation of glutathione levels. Oxaliplatin- and carboplatin-DNA adduct formation and repair was measured using accelerator mass spectrometry. Resistance factors including apoptosis, growth factor signaling and others were assessed with RNAseq of both cell lines and included confirmation of selected transcripts by RT-PCR. Oxaliplatin, carboplatin, cisplatin and gemcitabine were significantly less cytotoxic to 5637R cells compared to the 5637 cells. In contrast, doxorubicin, methotrexate and vinblastine had no cell line dependent difference in cytotoxicity. Upon exposure to therapeutically relevant doses of oxaliplatin, 5637R cells had lower drug-DNA adduct levels than 5637 cells. This difference was partially accounted for by pre-DNA damage mechanisms such as drug uptake and intracellular inactivation by glutathione, as well as faster oxaliplatin-DNA adduct repair. In contrast, both cell lines had no significant differences in carboplatin cell uptake, efflux and drug-DNA adduct formation and repair, suggesting distinct resistance mechanisms for these two closely related drugs. The functional studies were augmented by RNAseq analysis, which demonstrated a significant change in expression of 83 transcripts, including 50 known genes and 22 novel transcripts. Most of the transcripts were not previously associated with bladder cancer chemoresistance. This model system and the associated phenotypic and genotypic data has the potential to identify some novel details of resistance mechanisms of clinical importance to bladder cancer.

Abstract 905: Molecular dissection of platinum resistance through functional analysis

BACKGROUND: Platinum (Pt) agents (cisplatin, carboplatin and oxaliplatin) are active in many cancers including bladder cancer. Chemoresistance is the most common cause of treatment failure. This study is to determine the feasibility of using ultrasensitive accelerator mass spectrometry (AMS) to identify chemoresistance after cancer cells or patients are treated with one non-toxic microdose (1/100th of therapeutic dose) of Pt agents. The long-term goal is to identify chemoresistance before cancer patients receive toxic chemotherapy, and to determine the underlying resistance mechanisms to design personalized chemotherapy.

METHODS: Cellular sensitivity to chemotherapeutic agents was determined by the MTT assay. Platinum-induced DNA adduct formation and repair of adducts was measured with AMS after cells were exposed 14C-labeled carboplatin and oxaliplatin. AMS quantifies the 14C label that is attached to genomic DNA when the 14C-labled drug forms adducts with DNA. Cell uptake and efflux was measured by liquid scintillation counting. Intracellular glutathione levels were measured by colorimetric analysis.

RESULTS: Compared to the parental bladder cancer 5637 cells, chemoresistant 5637R cells are resistant to oxaliplatin (IC50: 2.45 µM versus 27.27 µM, p&lt;0.0001), and cisplatin (0.59 µM versus 2.99 µM, p=0.049), carboplatin (24.34 µM versus 72.18 µM, p&lt;0.0001), and gemcitabine (0.12 µM versus 1.44 µM, p=0.0015). Both 5637 and 5637R cells are still sensitive to other chemotherapeutic agents commonly used in treating bladder cancer, such as doxorubicin, methotrexate and vinblastine. Consistent with our hypothesis, chemoresistant 5637R cells have low oxaliplatin-induced DNA adduct levels than the parental 5637 cells (AUC of 943 versus 2,772 adducts per 109 nucleotide-hour for 5637, p=0.001). This low level of oxaliplatin-DNA adduct formation might be secondary to the pre-DNA damage mechanisms, such as decreased uptake (AUC of 4.42 versus 5.12 X 109 oxaliplatin molecules per cell for 5637, p=0.037) and increased intracellular inactivation of oxaliplatin by glutathione (53.91 versus 46.93 nmol/mg protein for 5637, p=0.003), plus increased repair of oxaliplatin-DNA adducts (3.48 versus 1.34 adducts per 108 nucleotides per hour for 5637, p=0.0004). We found the same correlation of low Pt-DNA adduct levels and chemoresistance in non-small cell lung (NSCLC) and breast cancer cell lines, and determined the same resistant mechanisms, such as cell uptake/efflux, intracellular inactivation and DNA repair. Carboplatin had partially different resistant mechanisms.

CONCLUSION: Functional analysis of major resistant steps can identify some chemoresistance mechanisms that can potentially help design personalized chemotherapy to overcome resistance. This approach can be applied to several different cancer types. A Phase 0 microdosing clinical trial is currently going on in patients with NSCLC and bladder cancer.

Citation Format: Amy W. Pan, Sisi Wang, Hongyong Zhang, Ruth Vinall, Tzu-yin Lin, Michael Malfatti, Maike Zimmermann, Tiffany Scharadin, Kenneth Turteltaub, Ralph de Vere White, Chong-xian Pan, Paul Henderson. Molecular dissection of platinum resistance through functional analysis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 905. doi:10.1158/1538-7445.AM2014-905

Nrdp1-mediated regulation of ErbB3 expression by the androgen receptor in androgen-dependent but not castrate-resistant prostate cancer cells

Patients with advanced prostate cancer (PCa) are initially susceptible to androgen withdrawal (AW), but ultimately develop resistance to this therapy (castration-resistant PCa, CRPC). Here, we show that AW can promote CRPC development by increasing the levels of the receptor tyrosine kinase ErbB3 in androgen-dependent PCa, resulting in AW-resistant cell cycle progression and increased androgen receptor (AR) transcriptional activity. CRPC cell lines and human PCa tissue overexpressed ErbB3, whereas downregulation of ErbB3 prevented CRPC cell growth. Investigation of the mechanism by which AW augments ErbB3, using normal prostate-derived pRNS-1-1 cells, and androgen-dependent PCa lines LNCaP, PC346C, and CWR22 mouse xenografts, revealed that the AR suppresses ErbB3 protein levels, whereas AW relieves this suppression, showing for the first time the negative regulation of ErbB3 by AR. We show that AR activation promotes ErbB3 degradation in androgen-dependent cells, and that this effect is mediated by AR-dependent transcriptional upregulation of neuregulin receptor degradation protein-1 (Nrdp1), an E3 ubiquitin ligase that targets ErbB3 for degradation but whose role in PCa has not been previously examined. Therefore, AW decreases Nrdp1 expression, promoting ErbB3 protein accumulation, and leading to AR-independent proliferation. However, in CRPC sublines of LNCaP and CWR22, which strongly overexpress the AR, ErbB3 levels remain elevated due to constitutive suppression of Nrdp1, which prevents AR regulation of Nrdp1. Our observations point to a model of CRPC development in which progression of PCa to castration resistance is associated with the inability of AR to transcriptionally regulate Nrdp1, and predict that inhibition of ErbB3 during AW may impair CRPC development.

Abstract 1702: Androgen receptor antagonist bicalutamide sensitizes androgen-independent prostate cancer cells to mTOR inhibitor rapamycin by regulating phosphorylation of translation initiation suppressor eIF4E-binding protein 1 (4E-BP1)

We previously showed that resistance of prostate cancer cells to the mTOR inhibitor rapamycin results from its ability to induce androgen receptor (AR) transcriptional activity, whereas co-treatment with the anti-androgen bicalutamide prevented this effect. Based on our data, collaborators at UC Davis Cancer Center are conducting a clinical trial to test the efficacy of this combination in patients with advanced prostate cancer. However, the mechanism by which the combination of rapamycin and bicalutamide work remains unknown. Investigation of the cause for resistance of prostate cancer cells to rapamycin showed that rapamycin-induced growth inhibition as well as AR transcriptional activity is mediated primarily by p70S6 kinase (S6K1), a downstream target of mTOR, but not by the 4E-BP1/eIF4E/eIF4G pathway, another downstream target of mTOR. Additionally, 4E-BP1 phosphorylation at Ser 65 was dose dependently inhibited by rapamycin in androgen-dependent LNCaP, but not in androgen-independent C4-2 cells, although rapamycin equally affected S6K1phosphorylation in both cells. Comparison of AR expression and 4E-BP1 phosphorylation in various prostate cancer cell lines demonstrated that those expressing high levels of the full-length AR also had increased 4E-BP1 phosphorylation, whereas no such relationship existed with S6K1. Hence, we investigated whether increased AR activity contributed to resistance of C4-2 cells to rapamycin-induced 4E-BP1 dephosphorylation. Bicalutamide treatment as well as culture in medium containing decreased levels of androgens repressed 4E-BP1 phosphorylation, showing that the AR is a positive regulator of 4E-BP1 phosphorylation. The combination of bicalutamide and rapamycin, but not rapamycin alone, inhibited 4E-BP1 phosphorylation in C4-2 cells. Additionally, bicalutamide sensitized PC-3 cells stably transfected with the AR, but not wild-type PC-3 cells that are AR null, to rapamyin-induced 4E-BP1 dephosphorylation. We also compared the effect of bicalutamide in two cell lines derived from CWR22 relapsed tumors: in CWR22R1 cell, which expressed significant levels of the full-length AR, 4E-BP1 phosphorylation was inhibited by bicalutamide, whereas in CWR22Rv1 cells, where the AR lack the ligand-binding domain (LBD), bicalutamide was unable to affect 4E-BP1 phosphorylation. Thus, in cells where bicalutamide is able to bind the AR, this drug sensitizes the cells to the effects of rapamycin. These results were verified in a CWR22 mouse xenograft model of prostate cancer progression. Taken together, our data show that rapamycin treatment increased AR activity by inhibiting S6K1, and that this increase in AR activity in turn induced resistance to rapamycin's ability to repress 4E-BP1 phosphorylation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1702.