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Proteomic Resistance Biomarkers for PI3K Inhibitor in Triple Negative Breast Cancer Patient-Derived Xenograft Models.

ABSTRACT: PI3K pathway activation is frequently observed in triple negative breast cancer (TNBC). However, single agent PI3K inhibitors have shown limited anti-tumor activity. To investigate biomarkers of response and resistance mechanisms, we tested 17 TNBC patient-derived xenograft (PDX) models representing diverse genomic backgrounds and varying degrees of PI3K pathway signaling activities for their tumor growth response to the pan-PI3K inhibitor, BKM120. Baseline and post-treatment PDX tumors were subjected to reverse phase protein array (RPPA) to identify protein markers associated with tumor growth response. While BKM120 consistently reduced PI3K pathway activity, as demonstrated by reduced levels of phosphorylated AKT, percentage tumor growth inhibition (%TGI) ranged from 35% in the least sensitive to 84% in the most sensitive model. Several biomarkers showed significant association with resistance, including elevated baseline levels of growth factor receptors (EGFR, pHER3 Y1197), PI3Kp85 regulatory subunit, anti-apoptotic protein BclXL, EMT (Vimentin, MMP9, IntegrinaV), NFKB pathway (IkappaB, RANKL), and intracellular signaling molecules including Caveolin, CBP, and KLF4, as well as treatment-induced increases in the levels of phosphorylated forms of Aurora kinases. Interestingly, increased AKT phosphorylation or PTEN loss at baseline were not significantly correlated to %TGI. These results provide important insights into biomarker development for PI3K inhibitors in TNBC.

SUBMITTER: Guo Z

PROVIDER: S-EPMC7765949 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Proteomic Resistance Biomarkers for PI3K Inhibitor in Triple Negative Breast Cancer Patient-Derived Xenograft Models.

Guo Zhanfang Z Primeau Tina T Luo Jingqin J Zhang Cynthia C Sun Hua H Hoog Jeremy J Gao Feng F Huang Shixia S Edwards Dean P DP Davies Sherri R SR Aft Rebecca R Ding Li L Ellis Matthew J MJ Li Shunqiang S Ma Cynthia X CX

Cancers 20201221 12

PI3K pathway activation is frequently observed in triple negative breast cancer (TNBC). However, single agent PI3K inhibitors have shown limited anti-tumor activity. To investigate biomarkers of response and resistance mechanisms, we tested 17 TNBC patient-derived xenograft (PDX) models representing diverse genomic backgrounds and varying degrees of PI3K pathway signaling activities for their tumor growth response to the pan-PI3K inhibitor, BKM120. Baseline and post-treatment PDX tumors were sub ...[more]

PMID: 33371187

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Project description:Extensive efforts, through cell line-based models, have been made to characterize the androgen receptor (AR) signaling pathway in triple-negative breast cancer (TNBC). However, these efforts have not yet reached a consensus with regards to the mechanism of AR in TNBC. Considering that patient-derived xenografts (PDXs) are more appropriate than cell line-based models for recapitulating the structural and molecular features of a patient's tumor, we have identified and molecularly characterized two new AR-positive TNBC PDX models and assessed the impacts of AR agonist [dihydrotestosterone (DHT)] and antagonist (enzalutamide) on tumor growth and gene expression profiles by utilizing immunohistochemistry, western blots, and RNA-Seq analyses. Two PDX models, termed TN1 and TN2, were derived from two grade-3 TNBC tumors, each harboring 1∼5% of AR nuclear positive cancer cells. DHT activated AR in both PDX tumors by increasing nuclear localization and AR protein levels. However, the endpoint tumor volume of DHT-treated TN1 was 3-folds smaller than that of non-treated TN1 tumors. Conversely, the endpoint tumor volume of DHT-treated TN2 was 2-folds larger than that of non-treated TN2. Moreover, enzalutamide failed to antagonize DHT-induced tumor growth in TN2. The RNA-Seq analyses revealed that DHT mainly suppressed gene expression in TN1 (961 down-regulated genes versus 149 up-regulated genes), while DHT promoted gene expression in TN2 (673 up-regulated genes versus 192 down-regulated genes). RNA-Seq data predicted distinct TNBC molecular subtypes for TN1 and TN2. TN1 correlated to a basal-like 1 (BL1) subtype, and TN2 correlated to a basal-like 2 (BL2) subtype. These analyses suggest that TN1 and TN2, which both express functional AR, are two molecularly distinct PDX models. The molecular characterization of these PDX models expands our current knowledge on AR-positive TNBC. Our results do not support that AR is a suitable therapeutic target in TNBC. To our best knowledge, the molecular mechanisms of AR in TNBC are equivocal and should be evaluated using clinically relevant models, considering both the heterogeneous expression of AR in TNBC and the general complexities of AR signaling.

Project description:Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer, with approximately 50% of patients having residual disease after neoadjuvant chemotherapy (NACT) and worse prognosis with higher residual cancer burden (RCB). Patient-derived xenograft (PDX) models of breast cancer are an effective discovery platform and tool for preclinical pharmacologic testing and biomarker identification. There is a need for PDX models encompassing the heterogeneity of TNBC both pre- and post- therapy and for identifying clinical and molecular features of patient’s tumors that are associated with success in establishing these models. Using fine-needle aspirates (FNAs), we established orthotopic PDX models of TNBC from the primary breast tumors of patients prior to and following neoadjuvant systemic therapy while enrolled in the ARTEMIS trial (NCT02276443). ARTEMIS is a prospective neoadjuvant clinical trial for women with primary TNBC who are treated with four cycles of Adriamycin combined with cyclophosphamide (AC) followed by taxane +/- different experimental therapies. Serial biopsies were obtained from patients prior to treatment (pre-therapy), from poorly responsive disease after four cycles of AC (mid-NACT), and in cases of AC-resistance, after a three-month course of different experimental therapies and/or additional chemotherapy (post-NACT). Our study cohort includes a total of 269 FNA biopsies from 217 women, generating a total of 62 successful PDX models (overall success-rate = 23%). This cohort includes five serial pre- and mid-NACT PDX pairs, as well as one serial pre-, mid-, post-NACT triplet. Success of PDX engraftment was generally higher from cancers that proved to be treatment-resistant: whether poor response to AC determined by ultrasound measurements mid-NACT (p=0.063), RCB II/III status after NACT (p=0.046), or metastatic relapse within two years of surgery (p=0.008). TNBC molecular subtype determined from gene expression microarrays of pre-NACT tumor revealed no significant association with PDX engraftment rate (p=0.877). Finally, we developed a statistical model predictive of PDX engraftment using percent Ki67 positive cells in the patient’s diagnostic biopsy, positive lymph node status at diagnosis, and low volumetric reduction of the patient’s tumor following AC treatment. This novel bank of 62 PDX models of TNBC provides a valuable resource for biomarker discovery and preclinical therapeutic trials aimed at improving neoadjuvant response rates for patients with TNBC.

Dataset Information

Proteomic Resistance Biomarkers for PI3K Inhibitor in Triple Negative Breast Cancer Patient-Derived Xenograft Models.

Publications

Proteomic Resistance Biomarkers for PI3K Inhibitor in Triple Negative Breast Cancer Patient-Derived Xenograft Models.

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