Abstract 449: Targeted proteomic analysis for personalized treatment of muscle invasive bladder cancer
Authors: Cecchi Fabiola , Thyparambil Sheeno , Blackler Adele , Hembrough Todd , Rabizadeh Shahrooz , Soon-Shiong Patrick , Frierson Henry , Theodorescu Daniel 
Published: July 2016

Background: Standard treatment for muscle-invasive bladder cancer (MIBC) includes chemotherapy with either gemcitabine-cisplatin (GC) or methotrexate, vinblastine, adriamycin and cisplatin (MVAC). These regimens have similar clinical complete response rates of approximately 30%. While no targeted treatment has been approved for bladder cancer, clinical trials have identified biochemical markers that predict the chemoresponsiveness of MIBC tumors to specific chemotherapeutic agents. For example, patients with high hENT1 and low RRM1 expression responded better to GC-based chemotherapy than their counterparts, and HER2 overexpression predicted resistance to cisplatin-based therapy. To quantify targets that are known indicators of tumor behavior, we used targeted proteomic analysis to assess 30 different protein biomarkers in formalin-fixed paraffin-embedded (FFPE) MIBC tumor tissue.

Methods: Twelve FFPE MIBC tissue blocks were obtained and a pathologist marked a minimum 8mm2 of tumor area from 1 or 2 slides. Following laser microdissection of the marked areas, proteins were extracted using the Liquid-Tissue® process and subjected to selected reaction monitoring mass spectrometry to quantify the amounts of 30 different targeted proteins in each patient sample.

Results: Of the 12 patient samples, 7 (58%) expressed high levels of hENT1 and 11 (92%) expressed low levels of RRM1, indicating that gemcitabine-based therapy would be an appropriate choice. A single patient expressed high levels of RRM1, an indication for non-gemcitabine based therapy. All 12 patients expressed TUBB3, a marker of resistance to taxane (vinblastine) and 10 patients (83%) lacked expression of FR-alpha, a marker of sensitivity to methotrexate. The majority of patients expressed a marker of sensitivity to anthracycline (TOPO2A) and did not express a resistance biomarker for platinum therapy (ERCC1).

Of 3 patients whose tumors expressed HER2, 2 had overexpression (&gt;750 amol/ug) and would thus be eligible for HER2 basket trials. Further, multiplex-targeted proteomics discovered patients expressing FGFR1 (17%), cMET (33%), Axl (17%) and IDO1 (25%), which would make them eligible for clinical trials of targeted or immunotherapies.

Conclusion: MIBC is heterogeneous and expresses a wide range of proteins. Yet, it continues to be treated with only 2 chemotherapeutic regimens. Multiplexed proteomics is currently being used in clinical practice to inform personalized patient care decisions with identification and the relative quantities of actionable proteins known to predict tumor behavior.

Citation Format: Fabiola Cecchi, Sheeno Thyparambil, Adele Blackler, Todd Hembrough, Shahrooz Rabizadeh, Patrick Soon-Shiong, Henry Frierson, Daniel Theodorescu. Targeted proteomic analysis for personalized treatment of muscle invasive bladder 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 449.