Genetic profiling and TCR repertoire feature of synchronous multiple primary lung carcinomas.

Abstract

e21031 Background: The incidence and detection rates of multiple primary lung cancer are increasing, as a result of the advances in lung cancer screening techniques. However, the molecular and immune mechanisms of their carcinogenesis were little known, which may have important diagnostic, prognostic and therapeutic implications. Methods: We retrospective analyzed 10 patients (pts) with clinically designated synchronous multiple primary lung cancers (sMPLC). 28 different tumor lesions were included and mutation profiles were analyzed using 1021 genes panel based next-generation sequencing (NGS). Meanwhile, the T-cell receptor (TCR) β repertoire of 28 tumor lesions and peripheral blood were analyzed by amplifying and sequencing the CDR3 region. T-cell clonality was defined as 1-normalized Shannon entropy, which was normalized by dividing Shannon entropy by the natural logarithm of the number of unique productive TCR sequences. Results: 8 of 10 pts were female and only one pts was smoker. The genetic profiles of 28 tissues were analyzed and almost no common mutations were detected between different tumors of one patient. The most common mutation was EGFR and it was detected in 11 tissues belonging to 7 pts. KRAS mutations were detected in 6 tissues belonging to 4 pts and only one patient detected both EGFR and KRAS mutation in different lesions. TP53 mutations were found in 6 tissues, which 5 co-existed with EGFR. Unlike the mutually exclusive between KRAS and EGFR, 4 pts were detected BRAF mutation whose other tissue aslo carried EGFR mutation. Next, we studied T-cell clonality, which ranges from 0 to 1 and describes the shape of T-cell frequency distribution. Analysis of TCR clonality revealed that this metric ranged from 0.092 in Pts T8 to 0.192 in Pts T5. Furthermore, heterogeneity of different lesions of pts was observed, with differences as large as 78% in T-cell clonality across different tumor lesions in Pts T2, which is bigger than difference of between patients. Beside, EGFR mutation lesions showed lower clonality but no significant differences (0.105 vs 0.130,p = 0.245). There no difference of number of non-synonymous mutation (NNSM) between EGFR-mutant and EGFR-wt group (3 vs 2, p = 0.748), and same in KRAS (3.5 vs 2, p = 0.410). However, frequency of share TCR of tissue and blood was positive correlated with NNSM (spearman r = 0.384,p = 0.048), which might means local immune microenvironment was related with regions mutation. Conclusions: Our results reveals independent molecular and immune feature of sMPLC pts, which may have contradictory therapeutic implications.