Polymorphism in autophagy gene ATG2B is not associated with bladder cancer recurrence after intravesical Bacillus Calmette-Guerin (BCG) immunotherapy in Asian patients.

Optimal patient stratification is critical in the era of personalized medicine. Germline polymorphisms play an important role in the treatment response of various human diseases, including bladder cancer. Intravesical BCG therapy is widely-used for bladder cancer. However, tumor recurrence and progression are very common. Stratification based on germline polymorphisms may contribute to circumvent this clinical challenge. Autophagy pathway plays an important role in the nonspecific protective effects of BCG. Patients that carry C allele of rs3759601 in autophagy gene ATG2B showed increased risk of recurrence and progression in European population. We thus sought to analyze rs3759601 and its relevance in BCG response in Asian NMIBC patients.

Functional impact of rs3759601 ATG2B (p.Gln1383Glu) was analyzed by bioinformatics programs including NCBI Conserved Domain Search, Clustal Omega, Polyphen and SIFT. NMIBC patients who received intravesical BCG at multiple hospitals in Singapore from 1995 to 2016 were included. These patients were genotyped for rs3759601 using high resolution melt analysis. The rs3759601 polymorphism was studied in correlation with the bladder cancer recurrence rate and disease progression rate in our cohort. Statistical analysis was conducted using Kaplan-Meier plots and the Chi-squared analysis.

In total, 307 individules were included in the study including 161 NMIBC patients and 146 healthy controls, predominately Chinese. The rs3759601 genotype distributions in our NMIBC patients were (GG 72.1%; GC 27.9%; CC 0%), which were distinct from the Dutch report (GG 32.8%; GC 47.4% and CC 19.8%, Buffen K et al, 2014). Consistently, the C allele frequencies of rs3759601 are 0.171 in our controls and 0.177 in East Asians from 1,000 Genome, but 0.406 in Europeans from 1,000 Genome. In silico analysis suggested rs3759601 ATG2B (p.Gln1383Glu) alteration is unlikely to be functionally deleterious. Statistical analysis revealed no significant association between ATG2B rs3759601 C allele and risk of bladder cancer recurrence (P= 0.353, GC vs. GG: hazard ratio [HR]= 1.324), or cancer progression (P= 0.454, GC vs. GG: HR = 0.658).

In contrast to European NMIBC patients, ATG2B rs3759601 C allele is much less common in Asians and it not associated with BCG response in Asian NMIBC patients.

Urologic oncology. 2020 Nov 26 [Epub ahead of print]

Zhijiang Zang, Yew Koon Lim, Yiong Huak Chan, Lata Raman, Kesavan Esuvaranathan, Edmund Chiong, Ratha Mahendran

Department of Urology, National University Hospital, National University Health System, Singapore. Electronic address: ., Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore., Biostatistics Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore., Department of Urology, National University Hospital, National University Health System, Singapore; Department of Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.