IDDF2022-ABS-0232 C8ORF76 promotes colorectal tumorigenesis by modulating immunosuppressive microenvironment and is a therapeutic target

Background

Copy number alterations are crucial for the development of colorectal cancer (CRC). We identified chromosome 8 open reading frame 76 (C8orf76) was preferentially amplified in CRC. We profiled the clinical significance and the molecular mechanism of C8orf76 in colorectal carcinogenesis.

Methods

The clinical implication of C8orf76 was determined in our human CRC cohorts. The biological function of C8orf76 was studied in vitro and in vivo. Transgenic C8orf76 knock-in mice were given azoxymethane plus dextran sulfate sodium (AOM-DSS) to induce colorectal carcinogenesis. Downstream effectors and signaling pathways were analyzed by ChIP-seq and RNA-seq. The therapeutic potential of C8orf76 was observed by using a xenograft mouse model by co-treated sgC8orf76 and anti-PD1.

Results

C8orf76 was upregulated in our CRC independent cohorts (P<0.0001) and further validated by TCGA cohort (P<0.0001). Ectopic expression of C8orf76 in colon cancer DLD1 and SW1116 cells promoted cell growth, clonogenicity, G1-S cell cycle progression, cell migration/invasion ability in vitro and promoted tumorigenicity, metastasis in vivo. Conversely, silencing of C8orf76 exerted significantly opposite effects. Transgenic C8orf76 knock-in significantly increased the colorectal tumor number and tumor load in AOM/DSS treated mice. Moreover, C8orf76 knock-in increased the frequencies of MDSCs, reduced the frequencies of CD8⁺T cells of the colon, and further impaired the function of CD8⁺T cells. RNA-seq identified that C8orf76 significantly activated PI3K-Akt signaling. Overlap of ChIP-seq and RNA-seq datasets identified that C8orf76 directly bound to the promoter region of N-Deacetylase And N-Sulfotransferase 1(NDST1) with a binding motif of GGCCAGCCTG and activated NDST1 transcription. NDST1 induced PI3K-Akt signaling and promoted colorectal tumorigenesis. Finally, C8orf76 knock out enhanced the anti-PD1 therapy efficacy in MC38 and CT26 xenograft mouse model, characterized by smaller tumor volume and tumor weight as well as enhanced immunity ability.

Conclusions

C8orf76 promotes colorectal tumorigenesis by activating PI3K-Akt signaling through binding to NDST1 and modulating the immunosuppressive microenvironment. C8orf76 is a potential therapeutic target for the treatment of CRC by synergizing with anti-PD1 treatment.