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Abstract Background Liver cancer is a highly malignant disease and the third leading cause of cancer death worldwide. Abnormal activation of PI3K/Akt signaling is common in cancer, but whether phosphoinositide‐3‐kinase regulatory subunit 3 (PIK3R3) plays a role in liver cancer is largely unexplored. Methods We determined the expression of PIK3R3 in liver cancer by using TCGA data and our clinical samples and knocked it down by siRNA or overexpressing it by the lentivirus vector system. We also investigated the function of PIK3R3 by colony formation, 5‐Ethynyl‐2‐Deoxyuridine, flow cytometry assay, and subcutaneous xenograft model. The downstream of PIK3R3 was explored by RNA sequence and rescue assays. Results We found that PIK3R3 was significantly upregulated in liver cancer and correlated with prognosis. PIK3R3 promoted liver cancer growth in vitro and in vivo by controlling cell proliferation and cell cycle. RNA sequence revealed that hundreds of genes were dysregulated upon PIK3R3 knockdown in liver cancer cells. CDKN1C, a cyclin‐dependent kinase inhibitor, was significantly upregulated by PIK3R3 knockdown, and CDKN1C siRNA rescued the impaired tumor cell growth. SMC1A was partially responsible for PIK3R3 regulated function, and SMC1A overexpression rescued the impaired tumor cell growth in liver cancer cells. Immunoprecipitation demonstrated there is indirect interaction between PIK3R3 and CNKN1C or SMC1A. Importantly, we verified that PIK3R3‐activated Akt signaling determined the expression of CDKN1C and SMC1A, two downstream of PIK3R3 in liver cancer cells. Conclusion PIK3R3 is upregulated in liver cancer and activates Akt signaling to control cancer growth by regulation of CDNK1C and SMC1A. Targeting PIK3R3 could be a promising treatment strategy for liver cancer that deserves further investigation.

Abstract Background Our previous study suggested that SMC1 has significant functions in colorectal cancer (CRC). However, few reports have shown the effects of structural maintenance of chromosomes 1 (SMC1A) on the immune microenvironment and tumor stem cells. Methods The Cancer Genome Atlas (TCGA) database, CPTAC database, Human Protein Atlas (HPA) database, the Cancer Cell Line Encyclopedia (CCLE) and Tumor Immune Single‐cell Hub were used. Flow cytometry and immunohistochemical analysis were checked for immune infiltration on MC38 mice model. Human CRC tissues were tested with RT‐qPCR. Results The mRNA and protein levels of SMC1A were increased in colon adenocarcinoma (COAD) samples. SMC1A was associated with DNA activity. Interestingly, SMC1A was highly expressed in many types of immune cells at single‐cell levels. Moreover, the high expression of SMC1A was positively correlated with immune infiltration, and immunohistochemical analysis showed that SMC1A was positively associated with CD45 expression in MC38 mice model. Also, the percentage of IL4+CD4+ T cells (Th2) and FoxP3+CD4+ T cells (Tregs) was significantly higher in the SMC1A overexpression group than in control by flow cytometry assay in vivo. SMC1A expression could affect the proliferation of T cells in the mice model. The mutation and somatic cell copy number variation (SCNV) of SMC1A were also associated with immune cell infiltration. In addition to SMC1A in the “hot” T‐cell inflammatory microenvironment of colon cancer, SMC1A also positively correlates with the immune checkpoint genes CD274, CTLA4, and PDCD1 in colon adenocarcinoma (COAD) samples. Furthermore, we also found that SMC1A plays a positive correlation with the induction of cancer stem cells (CSCs). Our results also showed that miR‐23b‐3p binds SMC1A. Conclusion SMC1A may be a bidirectional target switch that simultaneously regulates the immune microenvironment and tumor stem cells. Moreover, SMC1A may be a biomarker for the prediction of immune checkpoint inhibitor (ICI) therapy.

Background: Liver cancer is a highly malignant disease and the third leading cause of cancer death worldwide. Abnormal activation of PI3K/Akt signaling is common in cancer, but whether phosphoinositide‐3‐kinase regulatory subunit 3 (PIK3R3) plays a role in liver cancer is largely unexplored. Methods: We determined the expression of PIK3R3 in liver cancer by using TCGA data and our clinical samples and knocked it down by siRNA or overexpressing it by the lentivirus vector system. We also investigated the function of PIK3R3 by colony formation, 5‐Ethynyl‐2‐Deoxyuridine, flow cytometry assay, and subcutaneous xenograft model. The downstream of PIK3R3 was explored by RNA sequence and rescue assays. Results: We found that PIK3R3 was significantly upregulated in liver cancer and correlated with prognosis. PIK3R3 promoted liver cancer growth in vitro and in vivo by controlling cell proliferation and cell cycle. RNA sequence revealed that hundreds of genes were dysregulated upon PIK3R3 knockdown in liver cancer cells. CDKN1C, a cyclin‐dependent kinase inhibitor, was significantly upregulated by PIK3R3 knockdown, and CDKN1C siRNA rescued the impaired tumor cell growth. SMC1A was partially responsible for PIK3R3 regulated function, and SMC1A overexpression rescued the impaired tumor cell growth in liver cancer cells. Immunoprecipitation demonstrated there is indirect interaction between PIK3R3 and CNKN1C or SMC1A. Importantly, we verified that PIK3R3‐activated Akt signaling determined the expression of CDKN1C and SMC1A, two downstream of PIK3R3 in liver cancer cells. Conclusion: PIK3R3 is upregulated in liver cancer and activates Akt signaling to control cancer growth by regulation of CDNK1C and SMC1A. Targeting PIK3R3 could be a promising treatment strategy for liver cancer that deserves further investigation. PIK3R3 is upregulated in liver cancer and activates Akt signaling to control cancer growth by regulation of CDNK1C and SMC1A.Targeting PIK3R3 could be a promising treatment strategy for liver cancer that deserves further investigation. [ABSTRACT FROM AUTHOR]

Background: Our previous study suggested that SMC1 has significant functions in colorectal cancer (CRC). However, few reports have shown the effects of structural maintenance of chromosomes 1 (SMC1A) on the immune microenvironment and tumor stem cells. Methods: The Cancer Genome Atlas (TCGA) database, CPTAC database, Human Protein Atlas (HPA) database, the Cancer Cell Line Encyclopedia (CCLE) and Tumor Immune Single‐cell Hub were used. Flow cytometry and immunohistochemical analysis were checked for immune infiltration on MC38 mice model. Human CRC tissues were tested with RT‐qPCR. Results: The mRNA and protein levels of SMC1A were increased in colon adenocarcinoma (COAD) samples. SMC1A was associated with DNA activity. Interestingly, SMC1A was highly expressed in many types of immune cells at single‐cell levels. Moreover, the high expression of SMC1A was positively correlated with immune infiltration, and immunohistochemical analysis showed that SMC1A was positively associated with CD45 expression in MC38 mice model. Also, the percentage of IL4+CD4+ T cells (Th2) and FoxP3+CD4+ T cells (Tregs) was significantly higher in the SMC1A overexpression group than in control by flow cytometry assay in vivo. SMC1A expression could affect the proliferation of T cells in the mice model. The mutation and somatic cell copy number variation (SCNV) of SMC1A were also associated with immune cell infiltration. In addition to SMC1A in the "hot" T‐cell inflammatory microenvironment of colon cancer, SMC1A also positively correlates with the immune checkpoint genes CD274, CTLA4, and PDCD1 in colon adenocarcinoma (COAD) samples. Furthermore, we also found that SMC1A plays a positive correlation with the induction of cancer stem cells (CSCs). Our results also showed that miR‐23b‐3p binds SMC1A. Conclusion: SMC1A may be a bidirectional target switch that simultaneously regulates the immune microenvironment and tumor stem cells. Moreover, SMC1A may be a biomarker for the prediction of immune checkpoint inhibitor (ICI) therapy. [ABSTRACT FROM AUTHOR]