Immune microenvironment heterogeneity of concurrent adenocarcinoma and squamous cell carcinoma in multiple primary lung cancers

The molecular profiles and tumor immune microenvironment (TIME) of multiple primary lung cancers (MPLCs) presenting as concurrent lung adenocarcinoma (ADC) and squamous cell carcinoma (SQCC) remain unknown. We aimed to clarify these factors. We performed whole-exome sequencing (WES), RNA sequencing (RNA-Seq), and multiplex immunohistochemistry (mIHC) for five patients with concurrent ADC and SQCC. We found the genetic mutations were similar between ADC and SQCC groups. RNA-Seq revealed that the gene expression and pathways enriched in ADC and SQCC groups were quite different. Gene set enrichment analysis (GSVA) showed that nine gene sets were significantly differentially expressed between the ADC and SQCC groups (p < 0.05), with four gene sets relevant to squamous cell features upregulated in the SQCC group and five gene sets upregulated in the ADC group. Reactome enrichment analysis of differentially expressed genes showed that the immune function-related pathways, including programmed cell death, innate immune system, interleukin-12 family signaling, and toll-like receptor 2/4 pathways, etc. were significantly enriched. Transcriptomic TIME analysis, with mIHC in patient specimens and in vivo validation, showed tumor-infiltrating immune cells were significantly more enriched and diverse in ADC, especially CD8 + T cells. Our results revealed that the transcriptomic profiles and TIME features were quite different between ADC and SQCC lesions. ADC lesions exhibited a more active TIME than SQCC lesions in MPLCs.