Single-cell sequencing reveals MCAM(+) MyCAFs as key pro-angiogenic cells interacting with endothelial cells in solid-type adenoid cystic carcinoma.

BACKGROUND: Solid-type adenoid cystic carcinoma (ACC) is the most aggressive pathological type with the poorest prognosis. Extensive neovascularization and recruitment of cancer associated fibroblasts (CAFs) are the main characteristics, but the relationship between the two remains unclear. METHODS: Single-cell RNA sequencing was performed to classify and characterize CAFs in ACC. Primary CAFs from ACC were isolated and purified, and the pro-angiogenic capacity of CAFs from solid-type and non-solid-type ACC were compared. Finally, the upstream regulatory mechanisms of pro-angiogenic factor transcription were studied both in vitro and in vivo. RESULTS: Compared to non-solid-type ACC, CAFs in solid-type ACC are predominantly composed of melanoma cell adhesion molecule (MCAM)(+) myofibroblastic cancer-associated fibroblasts (myCAFs). The transcriptional levels of pro-angiogenic factors such as platelet-derived growth factor subunit A (PDGFA), platelet-derived growth factor subunit B (PDGFB), angiopoietin-1 (ANGPT1), and angiopoietin-2 (ANGPT2) in MCAM(+) myCAFs were significantly upregulated and exhibited stronger pro-angiogenic activity than MCAM(-) fibroblasts from non-solid-type ACC. In vivo experiments showed that MCAM(+) myCAFs mixed with the ACC cell line salivary gland adenoid cystic carcinoma cell line 83 (SACC83) had a stronger tumorigenic ability and induced more abundant microvascular formation compared to the implantation of SACC83 alone. Additionally, the transcription factor myocyte enhancer factor 2 C (MEF2C) was found to bind to the promoters of PDGFA, PDGFB, ANGPT1, and ANGPT2, initiating their transcription. Knockdown of MEF2C inhibited the pro-angiogenic activity of MCAM(+) myCAFs both in vitro and in vivo CONCLUSION: MCAM(+) myCAFs promote the transcription of pro-angiogenic factors through MEF2C, thereby enhancing angiogenesis and promoting tumor growth in solid-type ACC.