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SPARC is an acidic, cysteine-rich, calcium-binding member of the non-collagen glycoproteins originating in bone. Although implicated in the development of several cancers, the functions and mechanisms of SPARC remain unclear. The aim of this study was to investigate whether smooth muscle cell (SMC)-associated SPARC acts an important tumour suppressor in lung adenocarcinoma (LUAD). SPARC inhibits immune evasion in LUAD by suppressing CD276 functionality. We downloaded RNA-sequencing data from patients with LUAD in The Cancer Genome Atlas and identified a set of genes showing SMC-specific expression in these samples. We then screened for differentially expressed genes (DEGs). Enrichment analysis using the Gene Expression Omnibus identified key genes, while immune pathway analysis explored the expression of immune checkpoints involved in LUAD immune regulation. We further validated the differential expression of SPARC and CD276 using immunohistochemistry. Among the upregulated DEGs, SPARC exhibited high enrichment in SMCs, whereas 13 immune checkpoints, such as LAIR1 and CTLA4, were excluded. The infiltration level of the CD276 immune checkpoint was lower in the high-risk group than in the low-risk group. While our results suggest a correlation between SPARC, CD276 and LUAD, additional studies are needed to validate these findings and elucidate the underlying mechanisms before definitive conclusions can be drawn regarding their utility in clinical practice.
Zhao et al. (Tue,) studied this question.