Abstract 2106: Transcriptome analysis of patient-derived bladder cancer xenografts identifies genes associated with chemoresistance
Authors: Sebastian Aimy , Martin Kelly A. , Pan Chong-xian , Ma Ai-hong , deVere White Ralph W. , Loots Gabriela G. 
Published: July 2016

Background: Bladder cancer is among the ten most common cancers, with about ∼380,000 new cases and ∼150,000 deaths per year worldwide. Platinum-based combination chemotherapy is commonly used to treat advanced bladder cancer. It has been shown that only ∼50% of the patients with advanced bladder cancer respond to platinum-based therapy.

Methods: We employed a patient-derived bladder cancer xenograft (PDX) platform to characterize the molecular mechanisms contributing to resistance to gemcitabine-cisplatin combination therapy in advanced bladder cancer and to identify novel candidates that can be targeted to treat chemotherapy resistant bladder cancer. Transcriptome profiling of P0 (passage 0) bladder cancer xenograft tumors from 4 PDX lines (2 gemcitabine-cisplatin resistant lines and 2 drug sensitive lines) was performed by RNA-Seq analysis.

Results: PDXs retained the morphology fidelity and shared 92-97% of genetic alterations of parental cancer cells. The RNA-seq data suggested the presence of significant differences between the transcription profiles of drug-sensitive and drug-resistant tumors. We identified 333 genes &gt;2 fold up or down regulated in the drug resistant tumors compared to the drug sensitive tumors. Genes down-regulated in drug resistant tumors include tight junction protein CLDN3 and regulators of G-protein signaling RGS2 and RGS3. Significantly up-regulated genes include metabolic enzymes ALDH2, ALDH3A1, ALDH4A1 and ALDH7A1, transporter proteins ABCA1, SLC1A4, SLC2A5, SLC30A1, SLC39A6, SLC7A5 and SLC9A3, Notch ligand JAG2, Growth hormone receptor GHR and transmembrane glycoprotein GPNMB. Consistent with the change of cell surface proteins such as GHR and GPNMB, the MAPK and the PI3K-AKT pathways were upregulated when PDXs became resistant to cisplatin treatment.

Conclusion: Chemoresistance to gemcitabine and cisplatin is associated with altered expression of several cell surface proteins and upregulation of the downstream signaling pathways. Targeting these cell surface proteins can possibly be harnessed to overcome chemoresistance. GPNMB, a type I transmembrane protein highly up-regulated in the drug resistant tumors, has previously been shown to be over-expressed in various cancers. Targeting GPNMB with an antibody-drug-conjugate, glembatumumab vedotin, has shown promising results in treating several cancers including breast cancer and osteosarcoma. Further studies will elucidate whether targeting GPNMB is an effective strategy for the treatment of chemotherapy resistant bladder cancer.

Citation Format: Aimy Sebastian, Kelly A. Martin, Chong-xian Pan, Ai-hong Ma, Ralph W. deVere White, Gabriela G. Loots. Transcriptome analysis of patient-derived bladder cancer xenografts identifies genes associated with chemoresistance. [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 2106.