GSE183580
Homeoprotein SIX1 compromises anti-tumor immunity through TGF-ß-mediated regulation of collagens
Purpose: The tumor microenvironment (TME), such as non-immune-infiltrated “cold” tumors, has been associated with immune suppression. However, the complex mechanisms regulating tumor immunogenicity have not been clearly elucidated. In this study, we investigated whether Transcription factor sine oculis homeobox 1 (SIX1) expression in the cancer cells regulated anti-tumor immunity by reshaping TME. Methods: The expression of SIX1 in human tumor tissues was analyzed based on TCGA data. Six1 knockout murine cell lines were generated to analyze the SIX1-associated tumor progression and anti-tumor immune response in tumor xenograft models. Immune cells and cytokines in TME were quantified by immunofluorescence, flow cytometry, quantitative reverse transcription-PCR, and ELISPOT assay. SIX1-associated differentially expressed genes were investigated in cancer cells and tissues with RNA-Seq. At the end, Correlation of SIX1 with TGFBR2 expression was assessed by Western blot and Dual-luciferase reporter assay. Results:SIX1 was highly upregulated in human tumor tissues, while rarely expressed in matched normal tissues. Deletion of the Six1 in cancer cells inhibited tumor growth, depending on adaptive immunity. Moreover, Six1 deficiency significantly enhanced CD8+ T cells infiltration, leading to eradication of poorly immunogenic tumors and maintaining a long-term protection from tumor re-challenge. Mechanistically, SIX1 as a transcription factor upregulated TGFBR2 expression, which induced collagen genes expression via the Smad2/3 phosphorylation, increased collagens deposition in TME and hampered CD8+ T cells infiltration. Conclusions: Six1 deletion in cancer cells improved tumor immunogenicity, leading to tumor destruction by enhancing anti-tumor immune responses. Our observations uncovered a crucial role of SIX1 on remodulating tumor immunogenicity and demonstrated a proof of concept for targeting SIX1 in cancer immunotherapy. Overall design: mRNA profiles of MCA205 wild type (WT) and SIX1-/- cell lines or tumor tissue.