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Background <p>Most mutant <i>adenomatous polyposis coli</i> (<i>APC</i>) gene produced truncated APC protein (Trunc-APC), which has been shown to function as an oncogene in colorectal cancer (CRC) pathogenesis; however, its role in modulating innate immune responses within tumor cells remains unexplored.</p> Methods <p>We utilized CRISPR-Cas9 to knockout mutant <i>APC</i> and performed transcriptome sequencing across multiple CRC cell lines to investigate the immunomodulatory function of Trunc-APC. Subcellular fractionation, proteinase K protection assays, and immunofluorescence were employed to determine Trunc-APC subcellular localization. Protein interaction studies, ubiquitination assays, and aggregation analyses were conducted to elucidate Trunc-APC binding to MAVS and its impact on MAVS ubiquitination and RIG-I association. The effects of Trunc-APC deletion, alone or in combination with 5-azacytidine and trichostatin A, were evaluated on type I interferon activation, apoptosis, and tumor growth both in vitro and in vivo.</p> Results <p>We found that Trunc-APC partially localizes to the mitochondrial outer membrane and attenuates type I interferon signaling by binding to MAVS, suppressing its K63-linked polyubiquitination, and disrupting MAVS-RIG-I interactions. Deletion of Trunc-APC, particularly when combined with 5-azacytidine and trichostatin A, enhanced innate immune activation, promoted tumor cell apoptosis, and significantly inhibited CRC tumor growth both in vitro and in vivo.</p> Conclusions <p>Our study reveals a previously unrecognized role of Trunc-APC in dampening tumor-intrinsic innate immunity and suggests that co-targeting Trunc-APC with epigenetic therapy may offer a promising strategy to enhance anti-tumor immune responses in CRC.</p>

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Truncated APC impairs innate immune response by targeting MAVS on mitochondria in colorectal cancer

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月10日

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  • Si-Yu Li,
  • Xin-Yi Wang,
  • Jing Wang,
  • Jing-Hua Cao,
  • Yong-Rui Lv,
  • Dan Xie,
  • Feng-Wei Wang

摘要

Background

Most mutant adenomatous polyposis coli (APC) gene produced truncated APC protein (Trunc-APC), which has been shown to function as an oncogene in colorectal cancer (CRC) pathogenesis; however, its role in modulating innate immune responses within tumor cells remains unexplored.

Methods

We utilized CRISPR-Cas9 to knockout mutant APC and performed transcriptome sequencing across multiple CRC cell lines to investigate the immunomodulatory function of Trunc-APC. Subcellular fractionation, proteinase K protection assays, and immunofluorescence were employed to determine Trunc-APC subcellular localization. Protein interaction studies, ubiquitination assays, and aggregation analyses were conducted to elucidate Trunc-APC binding to MAVS and its impact on MAVS ubiquitination and RIG-I association. The effects of Trunc-APC deletion, alone or in combination with 5-azacytidine and trichostatin A, were evaluated on type I interferon activation, apoptosis, and tumor growth both in vitro and in vivo.

Results

We found that Trunc-APC partially localizes to the mitochondrial outer membrane and attenuates type I interferon signaling by binding to MAVS, suppressing its K63-linked polyubiquitination, and disrupting MAVS-RIG-I interactions. Deletion of Trunc-APC, particularly when combined with 5-azacytidine and trichostatin A, enhanced innate immune activation, promoted tumor cell apoptosis, and significantly inhibited CRC tumor growth both in vitro and in vivo.

Conclusions

Our study reveals a previously unrecognized role of Trunc-APC in dampening tumor-intrinsic innate immunity and suggests that co-targeting Trunc-APC with epigenetic therapy may offer a promising strategy to enhance anti-tumor immune responses in CRC.