Alexandra Corella

PIM1 kinase inhibition as a targeted therapy against triple-negative breast tumors with elevated MYC expression

Triple-negative breast cancer (TNBC), in which cells lack expression of the estrogen receptor (ER), the progesterone receptor (PR) and the ERBB2 (also known as HER2) receptor, is the breast cancer subtype with the poorest outcome. No targeted therapy is available against this subtype of cancer owing to a lack of validated molecular targets. We previously reported that signaling involving MYC—an essential, pleiotropic transcription factor that regulates the expression of hundreds of genes—is disproportionally higher in triple-negative (TN) tumors than in receptor-positive (RP) tumors. Direct inhibition of the oncogenic transcriptional activity of MYC has been challenging to achieve. Here, by conducting a shRNA screen targeting the kinome, we identified PIM1, a non-essential serine–threonine kinase, in a synthetic lethal interaction with MYC. PIM1 expression was higher in TN tumors than in RP tumors and was associated with poor prognosis in patients with hormone- and HER2-negative tumors. Small-molecule PIM kinase inhibitors halted the growth of human TN tumors with elevated MYC expression in patient-derived tumor xenograft (PDX) and MYC-driven transgenic mouse models of breast cancer by inhibiting the oncogenic transcriptional activity of MYC and restoring the function of the endogenous cell cycle inhibitor, p27. Our findings warrant clinical evaluation of PIM kinase inhibitors in patients with TN tumors that have elevated MYC expression.

Linking Tumor Mutations to Drug Responses via a Quantitative Chemical–Genetic Interaction Map

UNLABELLED There is an urgent need in oncology to link molecular aberrations in tumors with therapeutics that can be administered in a personalized fashion. One approach identifies synthetic-lethal genetic interactions or dependencies that cancer cells acquire in the presence of specific mutations. Using engineered isogenic cells, we generated a systematic and quantitative chemical-genetic interaction map that charts the influence of 51 aberrant cancer genes on 90 drug responses. The dataset strongly predicts drug responses found in cancer cell line collections, indicating that isogenic cells can model complex cellular contexts. Applying this dataset to triple-negative breast cancer, we report clinically actionable interactions with the MYC oncogene, including resistance to AKT-PI3K pathway inhibitors and an unexpected sensitivity to dasatinib through LYN inhibition in a synthetic lethal manner, providing new drug and biomarker pairs for clinical investigation. This scalable approach enables the prediction of drug responses from patient data and can accelerate the development of new genotype-directed therapies. SIGNIFICANCE Determining how the plethora of genomic abnormalities that exist within a given tumor cell affects drug responses remains a major challenge in oncology. Here, we develop a new mapping approach to connect cancer genotypes to drug responses using engineered isogenic cell lines and demonstrate how the resulting dataset can guide clinical interrogation.

Direct and indirect targeting of MYC to treat acute myeloid leukemia

PurposeAcute myeloid leukemia (AML) is the most common acute leukemia in adults and is often resistant to conventional therapies. The MYC oncogene is commonly overexpressed in AML but has remained an elusive target. We aimed to examine the consequences of targeting MYC both directly and indirectly in AML overexpressing MYC/Myc due to trisomy 8/15 (human/mouse), FLT3-ITD mutation, or gene amplification.MethodsWe performed in vivo knockdown of Myc (shRNAs) and both in vitro and in vivo experiments using four drugs with indirect anti-MYC activity: VX-680, GDC-0941, artemisinin, and JQ1.ResultsshRNA knockdown of Myc in mice prolonged survival, regardless of the mechanism underlying MYC overexpression. VX-680, an aurora kinase inhibitor, demonstrated in vitro efficacy against human MYC-overexpressing AMLs regardless of the mechanism of MYC overexpression, but was weakest against a MYC-amplified cell line. GDC-0941, a PI3-kinase inhibitor, demonstrated efficacy against several MYC-overexpressing AMLs, although only in vitro. Artemisinin, an antimalarial, did not demonstrate consistent efficacy against any of the human AMLs tested. JQ1, a bromodomain and extra-terminal bromodomain inhibitor, demonstrated both in vitro and in vivo efficacy against several MYC-overexpressing AMLs. We also confirmed a decrease in MYC levels at growth inhibitory doses for JQ1, and importantly, sensitivity of AML cell lines to JQ1 appeared independent of the mechanism of MYC overexpression.ConclusionsOur data support growing evidence that JQ1 and related compounds may have clinical efficacy in AML treatment regardless of the genetic abnormalities underlying MYC deregulation.

Abstract B34: PIM kinase as a novel therapeutic target for triple-negative breast cancer

The greatest clinical challenge in treating breast cancer occurs in those patients whose tumors lack expression of the estrogen and progesterone receptors and that of the HER2 oncoprotein. No targeted therapeutic strategies currently exist against this aggressive type of “triple negative” breast cancer (TNBC) due to lack of validated targets. We previously found that MYC mRNA, protein, and its signaling were disproportionally elevated in TN compared to receptor positive (RP) breast cancer. We sought to take advantage of the unique molecular feature found in this tumor type to identify potent and effective treatment strategies. Since MYC is an oncogenic transcription factor, rationally designed small molecule inhibitors that can directly inhibit its activity are not available for clinical use. An alternative approach to selectively kill MYC-driven tumors is to inhibit those proteins that are indispensable for the viability of such tumors, but are not essential in non-tumorigenic cells. This form of “indirect” treatment strategy has become known as the “synthetic-lethal” approach. To identify novel targets that are readily druggable for treating MYC-driven TNBC, we conducted a kinome MYC synthetic lethal shRNA screen in non-immortalized human mammary epithelial cells expressing a 4-hydroxytamoxifen (TAM)-activatable MycER transgene (HMEC-MycER). Of 600 human kinases targeted by 2,000 individual shRNA clones, 9 kinases were identified as hits as they were essential specifically for the MYC-activated HMEC cells. Among these hits, we focused on PIM1, a non-essential kinase, the knock-down of which had the greatest efficacy in causing cell death in the MYC-activated cells and had minimum inhibitory effect on the growth of the control cells. We determined that PIM1 expression was elevated in TN tumors and was associated with poor prognosis specifically in patients with hormone receptor-negative tumors. Small molecule PIM kinase inhibitors halted the growth of human TN tumors with elevated MYC expression in a patient-derived tumor xenograft (PDX) mouse model by inhibiting oncogenic transcriptional activity of MYC while simultaneously restoring the function of the endogenous cell cycle inhibitor p27. Thus, our findings warrant clinical evaluation of small molecule PIM kinase inhibitors in patients with TN tumors that exhibit elevated MYC expression. Note: This abstract was not presented at the conference. Citation Format: Dai Horiuchi, Alicia Y. Zhou, Alexandra N. Corella, Christina Yau, Sanjeev Balakrishnan, Kai Kessenbrock, Devon A. Lawson, Roman Camarda, Brittany N. Anderton, Alexey V. Bazarov, Henok Eyob, Julia Rohrberg, Paul Yaswen, Michael T. McManus, Hope S. Rugo, Zena Werb, Andrei Goga. PIM kinase as a novel therapeutic target for triple-negative breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr B34.

Abstract 2822: TPX2 overexpression is essential for the survival of MYC-driven triple negative breast cancer

Triple-negative breast cancer (TNBC) presents the most challenging subtype with the poorest clinical outcome and no targeted therapy. Our lab previously showed that oncogenic MYC pathways are deregulated in human TNBC tumors and predict patients’ poor prognosis. However, clinical development of small molecule inhibitors for MYC has not been successful yet. We identified a synthetic-lethal interaction in which inhibition of cyclin-dependent kinase 1 (CDK1) resulted in the selective killing of MYC overexpressing cancer cells. CDK1 is a mitotic kinase that regulates a large number of substrates and its inhibition causes proliferation arrest in all cells, which may be associated with toxicity. We hypothesize that the MYC-CDK1 synthetic lethality can be attributed to the loss of function of only one or a handful of CDK1 substrates. To identify those substrates, we combined bioinformatics analysis of gene expression data from patient samples and cell based screening approaches. We identified TPX2 depletion to efficiently kill MYC overexpressing cells, while sparing normal cells. Using analog-sensitive CDK1 we confirmed that TPX2 is a direct substrate of CDK1. TPX2 is highly overexpressed in TNBC and predicts patients’ poor prognosis. Its loss of function efficiently kills TNBC cells in a MYC dependent manner. We hypothesize that TPX2 is a novel synthetic lethal interaction partner of MYC. Our studies will help elucidate the biology of MYC-driven cancer such as TNBC, which will eventually lead to the development of less toxic and more efficacious targeted therapies. Citation Format: Julia Rohrberg, Alexandra Corella, Sanjeev Balakrishnan, Andrei Goga. TPX2 overexpression is essential for the survival of MYC-driven triple negative breast 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 2822.

Abstract C88: Genomics, advocacy, and emerging therapeutics to address triple-negative breast cancer (TNBC) outcome disparities.

Background: Collaborative team science provides a starting point for comprehensive change, and advocates have a unique and important role developing and engaging in transdisciplinary collaboratives that focus on new questions and new possibilities to advance the science of ethnic and medically underserved health care disparities. Participating in four areas : 1) research and programmatic support, 2) education and outreach, 3) policy and strategy, and 4) representation and advisory, the UCSF Breast Science Advocacy Core (BSAC) Program, a volunteer affiliate of the Breast Oncology Program (BOP), one of ten multidisciplinary research programs under the umbrella of the UCSF Helen Diller Comprehensive Cancer Center promotes a transformative, transdisciplinary, integrated environment to study the biological basis of the diseases that comprise breast cancer; to define the risk of developing or progressing with specific types of breast cancer; to develop novel interventions that work locally and globally to reduce morbidity and mortality from breast cancer and its treatment; and to leverage new collaborative research, education, and mentoring/training opportunities that address cancer outcome disparities. Advocates involved in KOMEN, DOD, PCORI, AND CBCRP funded research and training grants apply four core principles that forge synergy with NCI Advocacy Research Working Group Recommendations: 1)strategic innovation, 2)collaborative execution, 3)evidence based decision-making, and 4) ethical codes of conduct. Embracing transdisciplinary professionalism, researchers and advocates build on their track record as shared value partners committed to furthering the collective impact of science advocacy exchange (SAE). Study Objectives: Genomic analyses of patient tumors have unearthed an overwhelming number of recurrent somatic alterations in genes that have dramatic effects on tumor biology, patient drug responses, and clinical outcomes. In one study, high grade triple negative breast cancer (TNBC) accounts for 34% of breast cancers in African American women versus 21% in white women. A growing body of evidence has shown that African American women have biologically more aggressive disease, independent of social determinants, and suffer the highest mortality rates. While biological breakthroughs of the last decade have greatly advanced our understanding of cancer, in advanced TNBC, a poor prognosis subtype, there is an urgent need to translate this evolving patient genomic data into new therapeutic paradigms. Our study focuses on the intersection of synthetic lethal approaches, MYC driven human cancers, and immunotherapy as an “innovation agenda”. A distinct MYC vision highlights how overexpression is associated with aggressive outcomes and poor patient outcomes, and synthetic lethal strategies to target MYC (CDK inhibitors, PIM2, as well as the PDI immune pathways) have potential for addressing outcome disparities In African American Women with Triple Negative Breast Cancer (TNBC). Key Findings: We have developed a screening technique that can be used to rapidly and accurately identify potential synthetic lethal interactions in TNBC. This platform utilizes an isogenic cell line system that we have developed to model oncogene activation in TNBC. A growing body of evidence has shown that: 1) Quantitative approach maps genotype-specific drug responses in isogenic cells 2) Systematic discovery of biomarkers for cancer drugs under clinical investigation 3) Clinically actionable synthetic lethal interaction between MYC and dasatinib is discovered 4) Mechanism of dasatinib action through inhibition of LYN kinase is described Key Take-Away Message: The inclusion of advocates in convergent science settings remind academic stakeholders that research is there to benefit the patient as they attempt to spark innovation, democratize science, and support smarter interventions that expedite the incredible potential of future investments in bioscience within disparities arenas. Citation Format: Susan Samson, Alicia Y. Zhou, Maria Martins, Alexandra Corella, Dai Horiuchi, Christina Yau, Taha Rakshandehroo, John Gordan, Rebecca Levin, Jeff Johnson, John Jascur, Mike Shales, Antonio Sorrentino, Jaime Cheah, Paul Clemens, Alykhan Shamji, Stuart Schreiber, Nevan Krogan, Kevan Shokat, Frank McCormick, Sourav Bandyopadhyay, Andrei Goga. Genomics, advocacy, and emerging therapeutics to address triple-negative breast cancer (TNBC) outcome disparities. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C88.

Abstract B48: Identification of novel drug interactions with MYC via a quantitative chemical-genetic interaction map

There is an urgent need in oncology to link molecular aberrations in tumors with therapeutics that can be administered in a personalized fashion. One approach identifies synthetic-lethal genetic interactions or emergent dependencies that cancer cells acquire in the presence of specific mutations. Using engineered isogenic cells, we generated an unbiased and quantitative chemical-genetic interaction map that measures the influence of 51 aberrant cancer genes on 90 drug responses. The dataset strongly predicts drug responses found in cancer cell line collections, indicating that isogenic cells can model more complex cellular contexts. Applied to triple-negative breast cancer, we report clinically actionable interactions with the MYC oncogene including resistance to AKT/PI3K pathway inhibitors and an unexpected sensitivity to dasatinib through LYN inhibition in a synthetic-lethal manner, providing new drug and biomarker pairs for clinical investigation. This scalable approach enables the prediction of drug responses from patient data and can be used to accelerate the development of new genotype-directed therapies. Citation Format: Alicia Y. Zhou, Maria M. Martins, Alexandra Corella, Dai Horiuchi, Christina Yau, Taha Rakshandehroo, John D. Gordan, Rebecca S. Levin, Jeff Johnson, John Jascur, Mike Shales, Antonio Sorrentino, Jaime Cheah, Paul A. Clemons, Alykhan Shamji, Stuart L. Schreiber, Nevan J. Krogan, Kevan M. Shokat, Frank McCormick, Andrei Goga, Sourav Bandyopadhyay. Identification of novel drug interactions with MYC via a quantitative chemical-genetic interaction map. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr B48.

Abstract PR15: Functional analysis of diverse oncogenic driver mutations using an isogenic cell line library identifies novel drug responses and alterations in metabolism

There is an urgent need in oncology to link molecular aberrations in tumors with altered cellular behaviors, such as metabolic derangements, and to identify novel therapeutics for cancer treatment. We have sought to identify synthetic-lethal genetic interactions that cancer cells acquire in the presence of specific mutations. Using engineered isogenic cells, we generated an unbiased and quantitative chemical-genetic interaction map that measures the influence of 51 aberrant cancer genes on 90 drug responses. The dataset strongly predicts drug responses found in cancer cell line collections, indicating that isogenic cells can model more complex cellular contexts. Applied to triple-negative breast cancer, we report clinically actionable interactions with the MYC oncogene including resistance to PI3K/AKT pathway inhibitors and an unexpected sensitivity to dasatinib through LYN inhibition in a synthetic-lethal manner. These studies provide new drug and biomarker pairs for clinical investigation. We have also performed global metabolomics analysis in a subset of the isogenic cell lines demonstrating alterations in metabolic pathways that are shared across multiple oncogenes, as well as those that are distinct to specific oncogenic drivers. This scalable approach enables the prediction of drug responses from patient data and can be used to accelerate the development of new genotype-directed therapies. Citation Format: Maria M. Martins, Alicia Y. Zhou, Alexandra Corella, Dai Horiuchi, Christina Yau, Taha Rakshandehroo, John D. Gordan, Rebecca S. Levin, Jeff Johnson, John Jascur, Mike Shales, Antonio Sorrentino, Jaime Cheah, Paul A. Clemons, Alykhan Shamji, Stuart Schreiber, Stuart Schreiber, Nevan J. Krogan, Kevan M. Shokat, Kevan M. Shokat, Frank McCormick, Daniel Nomura, Sourav Bandyopadhyay, Andrei Goga. Functional analysis of diverse oncogenic driver mutations using an isogenic cell line library identifies novel drug responses and alterations in metabolism. [abstract]. In: Proceedings of the AACR Special Conference on Translation of the Cancer Genome; Feb 7-9, 2015; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(22 Suppl 1):Abstract nr PR15.

Abstract B44: A systems approach combining genomics, advocacy, and emerging novel therapeutics to address triple-negative breast cancer (TNBC) outcomes disparities

Background: Genomic analyses of patient tumors have unearthed an overwhelming number of recurrent somatic alterations in genes that have dramatic effects on tumor biology, patient drug responses, and clinical outcomes. In one study, high-grade triple negative breast cancer (TNBC) accounts for 34% of breast cancers in African American women versus 21% in white women. African American women have biologically more aggressive disease, independent of social determinants, and suffer the highest mortality rates. In advanced TNBC, a poor prognosis subtype, there is an urgent need to translate this emerging patient genomic data into new therapeutic paradigms. Objectives: Our study focuses on emerging compounds that are already approved (i.e., Dasatinib) or in testing for human use and we expect that this work will serve as a prelude to one or more clinical trials in TNBC. We seek to determine if the treatment of metastatic TNBC recurrence with more targeted genotype-specific agents could improve the outcomes/survival of all women in this particularly aggressive poor prognosis subset, including African American women. Methods: To guide the development of genotype-specific therapies in TNBC, we have established an isogenic cell-line drug screen that measures the impact of gene activation on a panel of emerging, clinically relevant compounds targeting a variety of cancer pathways. Using engineered isogenic cells, we generated an unbiased and quantitative chemical-genetic interaction map that measures the influence of 51 aberrant cancer genes on 90 drug responses. We believe that this approach can identify core synthetic lethal interactions, which underlie drug sensitivity and can be used as a foundation to identify patient populations that will selectively respond to drug treatments. Results: Using our systems approach, our interaction map highlights both known and novel connections between oncogene activation and drug responses and provides a modular roadmap for the exploration of synthetic lethal relationships. Applied to triple-negative breast cancer, we report clinically actionable interactions with the MYC oncogene including resistance to AKT/PI3K pathway inhibitors and an unexpected sensitivity to dasatinib through LYN inhibition in a synthetic-lethal manner. Ensuring that the voice of the patient is represented in our scientific inquiry, advocacy has played a significant role in the development and realization of this project. Aligning experiential and professionalized expertise, trained advocates explore relentless challenges and opportunities for moving the science forward. Conclusion: A novel systems biology approach that uses module maps of oncogenes and emerging therapeutics can define synthetic-lethal interactions and actionable therapeutics to help decrease TNBC outcomes/survival disparities in African American women. Citation Format: Alicia Y. Zhou, Maria M. Martins, Alexandra Corella, Dai Horiuchi, Christina Yau, Taha Rakshandehroo, John D. Gordan, Rebecca S. Levin, Jeff Johnson, John Jascur, Mike Shales, Antonio Sorrentino, Jaime Cheah, Paul A. Clemons, Alykhan Shamji, Stuart Schreiber, Nevan J. Krogan, Kevan M. Shokat, Frank McCormick, Susan Samson, Andrei Goga, Sourav Bandyopadhyay. A systems approach combining genomics, advocacy, and emerging novel therapeutics to address triple-negative breast cancer (TNBC) outcomes disparities. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr B44.

Abstract LB-122: PIM1 kinase inhibition halts the growth of MYC-overexpressing triple-negative breast tumors

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA The proto-oncogene MYC affects diverse cellular processes ranging from cell proliferation, metabolism, to pluripotency of embryonic stem cells. While de-regulated MYC signaling has been commonly identified in a variety of human malignancies, no therapeutic strategies have been clinically established to specifically target tumors that present elevated MYC expression. We have previously reported that triple-negative (TN) breast cancers, which lack the expression of predictive biomarkers of response (i.e., estrogen/progesterone receptors, human epidermal growth factor receptor 2), exhibit significantly elevated MYC expression as well as MYC pathway activation (Horiuchi, D., et al. 2012 JEM). To understand the vulnerabilities of TN tumors, we performed a kinome synthetic-lethal shRNA screen in human mammary epithelial cells in which MYC activity can be controlled (i.e., HMEC-MycER cells). The screen yielded 10+ potential synthetic lethal partners of MYC, including recently described AMPK-related kinase 5 (Liu, L., et al. 2012. Nature). One of our top hits was the proto-oncogene PIM1, a non-essential serine/threonine kinase previously shown to be a genetic enhancer of MYC in transgenic mouse models of lymphomas and prostate cancer. Our bioinformatics studies performed on four independent clinical cohorts (n: 146 ∼ 683 patients each) showed that in all cohorts both MYC and PIM1 were significantly enriched in the TN populations. PIM1 expression was correlated with that of MYC in three out of the four cohorts. Furthermore, we found that PIM1 overexpression alone was a poor prognostic factor associated with diminished recurrence-free survival. Our in vivo efficacy studies using conventional as well as novel “human-in-mouse,” patient derived orthotopic xenograft (PDX) models demonstrated that PIM was essential for the growth of MYC-overexpressing human TN tumors. In the PDX tumors, PIM inhibition nearly completely arrested tumor growth, which was associated with significant up-regulation of an endogenous cell cycle inhibitor p27, a known PIM1 substrate, down-regulation of protein synthesis machinery, and inhibition of MYC activity itself. These observations held true in a panel of breast cancer cell lines, and elevating the p27 expression alone was sufficient to inhibit cancer cell proliferation. Thus, our findings warrant the use of PIM kinase inhibitors in treating TN tumors that exhibit the elevated expression of MYC and/or PIM. Citation Format: Dai Horiuchi, Alicia Y. Zhou, Alexandra N. Corella, Christina Yau, Devon A. Lawson, Alexey V. Bazarov, Paul Yaswen, Michael T. McManus, Zena Werb, Alana L. Welm, Andrei Goga. PIM1 kinase inhibition halts the growth of MYC-overexpressing triple-negative breast tumors. [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 LB-122. doi:10.1158/1538-7445.AM2014-LB-122