Potential Of Asparagine Depletion For The Treatment Of Bladder Cancer And Other Urological Tumors

Due to asparagine synthetase (ASNS) deficiency, tumors cells auxotrophic for L-asparagine lack capability to synthesize this amino acid and depend to circulating L-asparagine for survival. Based on this rational, L-asparaginase (L-Aspa), an enzyme depleting L-asparagine, is an essential drug in the treatment of acute lymphoblastic leukemia (ALL), as these hematological cancer cells express low levels of ASNS. Recent evidence suggests that some solid tumors are also deficient in ASNS (Lorenzi, 2008; Dufour, 2012; Zhang, 2013), providing rationale for testing L-Aspa treatment in other contexts. In this study, we investigated the levels of ASNS expression in tumor tissues from patients with urological cancers (bladder, prostate and kidney) and we investigated the sensitivity to L-Aspa of bladder and prostate cell lines. Material & Method: ASNS expression was evaluated by a validated immunohistochemistry (IHC) method on tissue biopsie microarrays (USBiomax, Rockville, MD) including 384 cases of bladder, 94 cases of prostate and 75 cases of kidney tumors. A score was attributed to each tumor based on ASNS IHC labeling intensity from 0 (no labeling) to 3 (strong labeling). Tumors expressing no/low ASNS (scores 0 and 1) were considered potentially sensitive to asparagine depletion. Sensitivity to L-Aspa (expressed as an IC50) was assessed in vitro by measuring the cell viability of bladder cancer cell lines (RT-4 and UM-UC-3) and prostate cancer cell line PC-3 in the presence of various concentrations of L-Aspa. ASNS expression in cell lines was evaluated by western-blot. Results: ASNS expression was low/null in 77.3% of bladder tumors, 86.2% of prostate tumors and 72% of kidney tumors. In bladder tumors, no correlation was found between the grade of the tumor and its expression of ASNS. Bladder and prostate cancer cell lines were all sensitive to L-Aspa (IC50 = 0.31, 0.12 and 0.22 IU/mL for RT-4, UM-UC-3 and PC-3 cell lines, respectively) at a level similar to the sensitivity observed with the L-Aspa-sensitive MOLT-4 ALL cell line (IC50=0.19 IU/mL). All cell lines displayed low basal expression of ASNS. Conclusion: The sensitivity of bladder and prostate cancer cell lines to L-Aspa and the low/no expression of ASNS in the majority of urological tumor biopsies suggest that an extensive population of patients with urological tumors may respond to asparagine depletion. However, L-Aspa is accompanied with well known serious side-effects (hypersensitivity, coagulation disorders, pancreatitis, liver failure) and this drug should be used very carefully especially in older or frail patients. A new safer formulation is requested to make easier the clinical development of L-Aspa in urological cancer. Citation Format: Willy Berlier, Karine Aguera, Fanny Gallix, Fabien Gay, Gautam Borthakur, Yann Godfrin. Potential of asparagine depletion for the treatment of bladder cancer and other urological 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 5436. doi:10.1158/1538-7445.AM2014-5436