Mark Ozeck

An integrated genomic approach to identify predictive biomarkers of response to the aurora kinase inhibitor PF-03814735.

PF-03814735 is a novel, reversible inhibitor of Aurora kinases A and B that finished a phase I clinical trial for the treatment of advanced solid tumors. To find predictive biomarkers of drug sensitivity, we screened a diverse panel of 87 cancer cell lines for growth inhibition upon PF-03814735 treatment. Small cell lung cancer (SCLC) and, to a lesser extent, colon cancer lines were very sensitive to PF-03814735. The status of the Myc gene family and retinoblastoma pathway members significantly correlated with the efficacy of PF-03814735. Whereas RB1 inactivation, intact CDKN2A/p16, and normal CCND1/Cyclin D1 status are hallmarks of SCLC, activation or amplification of any of the three Myc genes (MYC, MYCL1, and MYCN) clearly differentiated cell line sensitivity within the SCLC panel. By contrast, we found that expression of Aurora A and B were weak predictors of response. We observed a decrease in histone H3 phosphorylation and polyploidization of sensitive lines, consistent with the phenotype of Aurora B inhibition. In vivo experiments with two SCLC xenograft models confirmed the sensitivity of Myc gene-driven models to PF-03814735 and a possible schedule dependence of MYC/c-Myc–driven tumors. Altogether our results suggest that SCLC and other malignancies driven by the Myc family genes may be suitable indications for treatment by Aurora B kinase inhibitors. Mol Cancer Ther; 11(3); 710–9. ©2012 AACR.

Biomarker and Pharmacologic Evaluation of the γ-Secretase Inhibitor PF-03084014 in Breast Cancer Models

Purpose: We aimed to assess the biologic activity of PF-03084014 in breast xenograft models. The biomarkers for mechanism and patient stratification were also explored. Experimental Design: The in vitro and in vivo properties of PF-03084014 were investigated. The mRNA expressions of 40 key Notch pathway genes at baseline or after treatment were analyzed to link with the antitumor efficacy of PF-03084014 in a panel of breast cancer xenograft models. Results: In vitro, PF-03084014 exhibited activity against tumor cell migration, endothelial cell tube formation, and mammosphere formation. In vivo, we observed apoptosis, antiproliferation, reduced tumor cell self-renewal ability, impaired tumor vasculature, and decreased metastasis activity after the treatment of PF-03084014. PF-03084014 treatment displayed significant antitumor activity in 10 of the 18 breast xenograft models. However, the antitumor efficacy in most models did not correlate with the in vitro antiproliferation results in the corresponding cell lines, suggesting the critical involvement of tumor microenvironment during Notch activation. In the tested breast xenograft models, the baseline expressions of the Notch receptors, ligands, and the cleaved Notch1 failed to predict the antitumor response to PF-03084014, whereas several Notch pathway target genes, including HEY2, HES4, and HES3, strongly corresponded with the response with a P value less than 0.01. Many of the best molecular predictors of response were also significantly modulated following PF-03084014 treatment. Conclusions: PF-03084014 showed antitumor and antimetastatic properties via pleiotropic mechanisms. The Notch pathway downstream genes may be used to predict the antitumor activity of PF-03084014 and enrich for responders among breast cancer patients. Clin Cancer Res; 18(18); 5008–19. ©2012 AACR.

PEST Domain Mutations in Notch Receptors Comprise an Oncogenic Driver Segment in Triple-Negative Breast Cancer Sensitive to a γ-Secretase Inhibitor

Purpose: To identify and characterize novel, activating mutations in Notch receptors in breast cancer and to determine response to the gamma secretase inhibitor (GSI) PF-03084014. Experimental Design: We used several computational approaches, including novel algorithms, to analyze next-generation sequencing data and related omic datasets from The Cancer Genome Atlas (TCGA) breast cancer cohort. Patient-derived xenograft (PDX) models were sequenced, and Notch-mutant models were treated with PF-03084014. Gene-expression and functional analyses were performed to study the mechanism of activation through mutation and inhibition by PF-03084014. Results: We identified mutations within and upstream of the PEST domains of NOTCH1, NOTCH2, and NOTCH3 in the TCGA dataset. Mutations occurred via several genetic mechanisms and compromised the function of the PEST domain, a negative regulatory domain commonly mutated in other cancers. Focal amplifications of NOTCH2 and NOTCH3 were also observed, as were heterodimerization or extracellular domain mutations at lower incidence. Mutations and amplifications often activated the Notch pathway as evidenced by increased expression of canonical Notch target genes, and functional mutations were significantly enriched in the triple-negative breast cancer subtype (TNBC). PDX models were also identified that harbored PEST domain mutations, and these models were highly sensitive to PF-03084014. Conclusions: This work suggests that Notch-altered breast cancer constitutes a bona fide oncogenic driver segment with the most common alteration being PEST domain mutations present in multiple Notch receptors. Importantly, functional studies suggest that this newly identified class can be targeted with Notch inhibitors, including GSIs. Clin Cancer Res; 21(6); 1487–96. ©2015 AACR.

HIP1–ALK, A Novel ALK Fusion Variant that Responds to Crizotinib

Introduction: The aim of this study was to identify anaplastic lymphoma kinase (ALK) rearrangements in lung cancer patient-derived xenograft (PDX) models and to explore their responses to crizotinib. Methods: Screening of 99 lung cancer PDX models by the NanoString ALK fusion assay identified two ALK-rearranged non–small-cell lung cancer (NSCLC) tumors, including one harboring a previously known echinoderm microtubule-associated protein-like 4 (EML4)–ALK fusion and another containing an unknown ALK fusion variant. Expression array, RNA-Seq, reverse transcription polymerase chain reaction, and direct sequencing were then conducted to confirm the rearrangements and to identify the novel fusion partner in the xenograft and/or the primary patient tumor. Finally, pharmacological studies were performed in PDX models to evaluate their responses to ALK inhibitor crizotinib. Results: Two ALK-rearranged NSCLC PDX models were identified: one carried a well-known EML4–ALK variant 3a/b and the other harbored a novel huntingtin interacting protein 1 (HIP1)–ALK fusion gene. Exon 28 of the HIP1 gene located on chromosome 7 was fused to exon 20 of the ALK gene located on chromosome 2. Both cases were clinically diagnosed as squamous cell carcinoma. Compared with the other lung cancer PDX models, both ALK-rearranged models displayed elevated ALK mRNA expression. Furthermore, in vivo efficacy studies demonstrated that, similar to the EML4–ALK-positive model, the HIP1–ALK-containing PDX model was sensitive to treatment with crizotinib. Conclusions: Discovery of HIP1 as a fusion partner of ALK in NSCLC is a novel finding. In addition, the HIP1–ALK-rearranged tumor is sensitive to treatment with crizotinib in vivo, implicating HIP1–ALKas an oncogenic driver of lung tumorigenesis. Collectively, our results indicate that HIP1–ALK-positive NSCLC may benefit from clinical applications of crizotinib.

Molecular Predictors of Sensitivity to the Insulin-like Growth Factor 1 Receptor Inhibitor Figitumumab (CP-751,871)

Figitumumab (CP-751,871), a potent and fully human monoclonal anti–insulin-like growth factor 1 receptor (IGF1R) antibody, has been investigated in clinical trials of several solid tumors. To identify biomarkers of sensitivity and resistance to figitumumab, its in vitro antiproliferative activity was analyzed in a panel of 93 cancer cell lines by combining in vitro screens with extensive molecular profiling of genomic aberrations. Overall response was bimodal and the majority of cell lines were resistant to figitumumab. Nine of 15 sensitive cell lines were derived from colon cancers. Correlations between genomic characteristics of cancer cell lines with figitumumab antiproliferative activity revealed that components of the IGF pathway, including IRS2 (insulin receptor substrate 2) and IGFBP5 (IGF-binding protein 5), played a pivotal role in determining the sensitivity of tumors to single-agent figitumumab. Tissue-specific differences among the top predictive genes highlight the need for tumor-specific patient selection strategies. For the first time, we report that alteration or expression of the MYB oncogene is associated with sensitivity to IGF1R inhibitors. MYB is dysregulated in hematologic and epithelial tumors, and IGF1R inhibition may represent a novel therapeutic opportunity. Although growth inhibitory activity with single-agent figitumumab was relatively rare, nine combinations comprising figitumumab plus chemotherapeutic agents or other targeted agents exhibited properties of synergy. Inhibitors of the ERBB family were frequently synergistic and potential biomarkers of drug synergy were identified. Several biomarkers of antiproliferative activity of figitumumab both alone and in combination with other therapies may inform the design of clinical trials evaluating IGF1R inhibitors. Mol Cancer Ther; 12(12); 2929–39. ©2013 AACR.

A NOTCH1 gene copy number gain is a prognostic indicator of worse survival and a predictive biomarker to a Notch1 targeting antibody in colorectal cancer

Dysregulation of the Notch1 receptor has been shown to facilitate the development and progression of colorectal cancer (CRC) and has been identified as an independent predictor of disease progression and worse survival. Although mutations in the NOTCH1 receptor have not been described in CRC, we have previously discovered a NOTCH1 gene copy number gain in a portion of CRC tumor samples. Here, we demonstrated that a NOTCH1 gene copy number gain is significantly associated with worse survival and a high percentage of gene duplication in a cohort of patients with advanced CRC. In our CRC patient‐derived tumor xenograft (PDTX) model, tumors harboring a NOTCH1 gain exhibited significant elevation of the Notch1 receptor, JAG1 ligand and cleaved Notch1 activity. In addition, a significant association was identified between a gain in NOTCH1 gene copy number and sensitivity to a Notch1‐targeting antibody. These findings suggest that patients with metastatic CRC that harbor a gain in NOTCH1 gene copy number have worse survival and that targeting this patient population with a Notch1 antibody may yield improved outcomes.

Abstract 1958: Interrogating hedgehog pathway and smoothened inhibition by PF-04449913 in patient-derived acute myeloid leukemia models

Aberrant activation of the Hedgehog (Hh) signaling pathway has been implicated in a variety of cancers and a small molecule inhibitor of Smoothened (SMO), Vismodegib, has been approved for the treatment of basal cell carcinoma, a disease frequently driven by Hh pathway signaling due to pathway mutations. SMO dependent Hh signaling has also been implicated in models of myeloid leukemia, primarily CML, where genetic loss of SMO or pharmacological inhibition limits disease progression in part through targeting the leukemic stem cell (LSC). Outside of BCR-ABL driven leukemia the role of Hh signaling and impact of SMO inhibition on disease progression and the LSC remains unclear. To explore the role of Hedgehog pathway signaling and interrogate responses to SMO inhibition in AML, a panel of primary AML patient-derived models was utilized to examine responses to PF-04449913, an oral small molecule SMO inhibitor currently in early phase clinical trials targeting myeloid malignancies. AML patient samples were characterized for Hh pathway expression levels and screened for responses to PF-04449913. Ex vivo treatment of AML bone marrow cells showed PF-04449913 was capable of inhibiting Hh pathway activity, reducing expression of key LSC regulators and decreasing populations of cells expressing LSC markers. Use of AML xenotransplant models to assess in vivo responses to PF-04449913 as single agent and in combination with Cytarabine have shown potential for combination efficacy of the two agents in select models suggesting patient selection strategies may be critical for SMO inhibitor-based therapies in AML. Citation Format: Amy Jackson-Fisher, Pamela Whalen, Mark Elliott, Melissa McMahon, Enhong Chen, Xianxian Zheng, Mark Ozeck, Donghui Huang, Paul Lira, Joseph Lee, Cathy Zhang, Justine Lam, Mary Spilker, Shibing Deng, Patrick Lappin, Penny Venne, Cynthia Heinlein, Annelie Schairer, Karen McLachlan, Todd VanArsdale. Interrogating hedgehog pathway and smoothened inhibition by PF-04449913 in patient-derived acute myeloid leukemia models. [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 1958. doi:10.1158/1538-7445.AM2014-1958

Abstract A1-52: Identification of drug-sensitive Notch receptor alterations in human breast cancer

While the Notch pathway is reportedly activated in breast cancer, the molecular mechanisms leading to its aberrant activation remain elusive, hampering the optimal development of Notch inhibitors in the clinics. In an effort to identify predictive biomarkers of response to Notch targeted therapies in breast cancer, we used several computational approaches, including novel algorithms for detecting complex structural rearrangements, to analyze next generation sequencing and related omic datasets from The Cancer Genome Atlas (TCGA) breast cancer cohort. We identified simple mutations and complex rearrangements in NOTCH1, NOTCH2 and NOTCH3 that compromised the function of the PEST domain, a negative regulatory domain controlling the duration of active Notch signaling. Focal amplifications of NOTCH2 and NOTCH3 were also observed, as were heterodimerization or extracellular domain alterations, at lower incidence. Mutations and amplifications often activated the Notch pathway as evidenced by increased expression of canonical Notch target genes, and functional mutations were significantly enriched in the triple negative breast cancer (TNBC) subtype. We also sequenced a panel of breast cancer xenograft models and identified models that harbor functionally equivalent PEST domain alterations. These models were significantly more sensitive to a gamma secretase inhibitor (GSI) compared to models without Notch alterations. Gene expression and functional analyses were performed to study the mechanism of activation through mutation and inhibition by GSI. In summary, we demonstrated that Notch pathway is activated via multiple mutational mechanisms primarily involving the PEST domains of NOTCH1, NOTCH2 and NOTCH3. Collectively, approximately 13% of TNBC exhibits a genetic alteration coupled with pathway up-regulation and these alterations may serve as biomarkers to identify patients most likely to respond to Notch inhibitors. Citation Format: Kai Wang, Qin Zhang, Danan Li, Keith Ching, Cathy Zhang, Xianxian Zheng, Mark Ozeck, Stephanie Shi, Xiaorong Li, Hui Wang, Paul Rejto, James Christensen, Peter Olson. Identification of drug-sensitive Notch receptor alterations in human breast cancer. [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 A1-52.

Abstract A2-33: Molecular profiling of patient-derived xenograft models across cancers

Patient-Derived Xenograft (PDX) provides important preclinical model for pharmacological testing of oncology drug candidates. Molecular profiling of PDX tumors contributes to many areas of drug discovery from target discovery to development of clinical biomarker hypotheses and clinical trial design. We established a work flow to perform genomic and histopathology analyses of large numbers of PDX tumor models being made available for Pfizer internal research. To date we have generated whole-genome sequencing (WGS), whole-exome sequencing (WES) and whole transcriptome sequencing (RNA-Seq) data on PDX models spanning six cancer types including colon, pancreatic and breast cancers. Bioinformatics pipelines were developed to quantify gene expression and detect genetic alterations including mutation, copy number variations and gene fusions. A controlled evaluation study demonstrated that in silico classification of NGS reads into human/mouse origins is more effective than laboratory-based methods for removing mouse tissue contamination. Comparative analyses of molecular profiles from PDX and primary tumors of the same cancer origins suggest that important patterns of gene expression are retained by PDX models. An integrative genomic classifier was developed using the random forest algorithm, trained on primary tumor data, and shown to identify PDX cancer subtypes with high accuracy. Citation Format: Zhengyan Kan, Edward Rosfjord, James Hardwick, Ying Ding, Xianxian Zheng, Julio Fernandez, Stephanie Shi, Mark Ozeck, Hui Wang, Gabriel Troche, Eric Upeslacis, Amy Jackson-Fisher, Keith Ching, Shibing Deng, Xie Tao, John Chionis, Maruja Lira, Xiaorong Li, Konstantinos Tsaparikos, Patrick Lappin, Pamela Vizcarra, David Shields, Judy Lucas, Paul Rejto. Molecular profiling of patient-derived xenograft models across cancers. [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 A2-33.

Abstract 940: Identification of Palbociclib response signature across indications

Cellular proliferation is dependent on an orderly movement through the various phases of cell cycle. Progression through the G1 phase in particular requires phosphorylation of the retinoblastoma (Rb) protein which in turn releases E2F transcription factors resulting in transcriptional activation of response gene necessary for progression into S-phase. The cyclin D-CDK4/6 signaling pathway represent a critical regulatory pathway controlling transition from G1 into S-phase and greater than 90% of human tumors have mutations in this pathway. Palbociclib is a potent, selective, and orally bioavailable inhibitor of Cdk4/6. In human tumor xenograft models, Palbociclib has significant antitumor activities. The clinical activities of Palbociclib have also be demonstrated in the phase II PALOMA-1 trial for dramatic efficacy of postmenopausal patients with locally advanced or newly diagnosed estrogen receptor (ER)-positive, HER2-negative metastatic breast cancer in combination with letrozole. To better understand the molecular mechanisms of Palbociclib response, we have identified a common set of gene signatures for ER+ BC as well as melanoma models. The physiological role of these genes regulated by Palbociclib is associated with DNA replication and repair, cell cycle, signal transduction, and Mitosis. Many of these genes have been previously identified as E2F signatures. In this study, we are aiming to expand this analysis to include two additional indications including Head and Neck squamous cell carcinoma (HNSCC) as well as squamous cell lung carcinoma (Sq lung) using Illumina RNASeq technology platform. Results from these studies will be presented and core Palbo-response signature will be discussed. In addition, we will also present the pharmacological effects of Letrozole on the gene expression changes for these core signatures in ER+ BC models. Citation Format: Xianxian Zheng, Mark Ozeck, Zhou Zhu, Keith Ching, David Shields, James Hardwick, Paul Rejto, Todd VanArsdale. Identification of Palbociclib response signature across indications. [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 940. doi:10.1158/1538-7445.AM2015-940