Whole exome sequencing reveals molecular mechanisms of clear cell renal cell carcinoma with sarcomatoid differentiation

Objective: To investigate the molecular mechanisms of clear cell renal cell carcinoma (CCRCC) with sarcomatoid differentiation (CCRCCS) and to explore new therapeutic targets for CCRCCS. Methods: Whole exome sequencing was performed on the carcinomatous and sarcomatoid components of five CCRCCS cases collected from January 2017 to October 2018. A highly frequent non-synonymous mutation of cadherin 23 (CDH23) was revealed by whole exome sequencing and further studied in additional samples. The sequencing of CDH23 in 40 specimens with CCRCCS and 50 specimens with CCRCC collected from January 2008 to October 2018 were conducted using Sanger sequencing. Immunohistochemistry was carried out to detect the protein expression of CDH23 in the additional 90 cases. Results: Carcinomatous and sarcomatoid components of CCRCCS shared most of the somatic single-nucleotide variants (SSNVs) as revealed through whole exome sequencing, while the sarcomatoid component had higher overall SSNVs than carcinomatous component. A highly frequent non-synonymous mutation of CDH23 (p.Arg1804Gln) was observed both in carcinomatous and sarcomatoid components of CCRCCS that resulted in the alteration in the highly conserved calcium-binding site mediating the functions of cadherins. In the additional 90 specimens, CDH23 mutation was much frequently detected in CCRCCS than that in CCRCC samples and even the high grade CCRCC. CDH23 protein was not or weakly expressed in most CCRCCS specimens with CDH23 mutation. There was an correlation between CDH23 gene mutation and negative expression of its protein (r=0.598, P<0.01). Conclusions: The present study reveals, for the first time, that the mutation of CDH23 (p.Arg1804Gln) is a genetic risk factor for CCRCCS. It is associated with the decreased expression of CDH23 protein, resulting in the absence of cadherin function of CDH23, indicating that CDH23 mutation may be involved in the sarcomatoid transformation in CCRCCS. Thus, CDH23 might be a potential therapeutic target for CCRCCS.