Heterochromatin protein 1γ (CBX3) links histone methylation marks to transcriptional silence, DNA repair and RNA splicing, but a role for CBX3 in cancer remains largely unknown. In this study, we show that CBX3 in colon cancer cells promotes the progression of the cell cycle and proliferation in vitro and in vivo. Cell cycle (G1 phase to S phase) related gene CDK6 and p21 were further identified as targets of CBX3. In addition, we found that enhancing CDK6 suppresses cell proliferation by upregulating inhibitor p21 in the absence of CBX3, and this function is independent of the kinase activity of CDK6. Our results demonstrate a key role of CBX3 in colon carcinogenesis via suppressing the expression of CDK6/p21, which may disrupt the role of CDK6 in transcriptionally regulating p21, as part of a negative feedback loop to limit CDK6 excessive activation.

Background:A retrospective analysis verified the role of gene mutations in brain metastasis in patients with non-small cell lung cancer (NSCLC). Methods: Data from 552 patients with advanced NSCLC treated from January 2015 to June 2017 in the Affiliated Cancer Hospital of Zhengzhou University were retrospectively analyzed. Next-generation sequencing was used to detect mutations in eight reported driver genes and various risk factors were evaluated. Results: Of the 552 patients with advanced NSCLC, 153 (27.7%) had brain metastases. The univariate analysis showed that age (P = .008), gender (P = .016), smoking history (P = .010), lymph node metastasis (P = .003), and three driver genes, positive epidermal growth factor receptor (EGFR) mutation (P = .001), positive anaplastic lymphoma kinase (ALK) gene fusion (P = .021), and positive rearranged during transfection (RET) gene fusion (P = .003), were the factors influencing the incidence of brain metastasis. Logistic multivariate regression analysis revealed that positive EGFR mutation (P = .012), positive ALK gene fusion (P = .015), positive RET gene fusion (P = .003), pathological type (P = .009), lymph node N2-3 metastasis (P < .001), and a younger age (P < .001) were independent risk factors for brain metastasis. In addition, a receiver operating characteristic (ROC) curve was plotted with the above factors with an area under the curve = 0.705 (P < .001). Conclusions: An EGFR mutation, ALK gene fusion, and RET gene fusion in advanced NSCLC patients play roles in brain metastasis as positive driver genes. Impact: An EGFR mutation, and ALK and RET gene fusions are risk factors for brain metastasis in advanced NSCLC patients. K E Y W O R D Sbrain metastases, clinicopathological features, driver genes, lung cancer, non-small cell lung cancer (NSCLC), targeted therapy

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