Melanocytes derived from neural crest cells harbor the BRAFV600E mutation,which is the predominant driver of nevus formation in humans.This mutation leads to malignant cell proliferation and subsequent cell cycle arrest,culminating in oncogene-induced senescence and nevus development.Nevertheless,emerging evidence has highlighted the heterogeneity of cellular senescence markers in BRAFV600E-induced senescent melanocytes.Moreover,the capacity of melanocytes within nevi to regain their proliferative ability raises questions about the molecular mechanisms by which BRAFV600E,via the mitogen-activated protein kinase signaling pathway,triggers nevus formation.This study provides an overview and discussion of the molecular mechanisms underpinning BRAFV600E-induced melanocyte nevus formation and the relevant animal models employed for their elucidation.It also highlights the significance of elucidating dynamic changes in cytoplasmic and nuclear substrates that interact with phosphorylated extracellular signal-regulated protein kinases 1 and 2 and underscores the value of using targeted BRAFV600E animal models created through gene editing technologies.

Objective To analyze the sensitivity of ARHGAP8 in predicting the efficacy of neoadjuvant chemotherapy in the patients with locally advanced mid-low colorectal cancer and provide accurate evidence for the treatment of advanced colorectal cancer.Methods The differentially expressed gene ARHGAP8 was screened out by bioinformatics analysis.Cancer tissue and rectal tissue of 68 patients with primary rectal cancer were select-ed.The rectal cancer tissue samples and the rectal tissue samples were collected for clinical validation of ARH-GAP8 expression by quantitative real-time PCR,Western blotting,and immunohistochemistry.The clinical and pathological features such as gender,age,tumor stage,differentiation degree,and pathological type of the pa-tients were collected for functional validation.Forty-four patients with locally advanced mid-low rectal cancer who received neoadjuvant chemotherapy were selected for immunohistochemical examination of ARHGAP8 expres-sion.The expression level of ARHGAP8 was compared between before and after chemotherapy and among different efficacy groups.Results The bioinformatics analysis revealed differences in the expression level of ARHGAP8 between the cancer tissue and rectal tissue(P＜0.001).The expression level of ARHGAP8 was correlated with tumor stage(P=0.024),lymph node metastasis(P=0.007),and age(P=0.005).Quantitative real-time PCR results showed that the mRNA level of ARHGAP8 in the cancer tissue was higher than that in the rectal tis-sue(P＜0.001).Western blotting and immunohistochemistry results demonstrated that the protein level of ARH-GAP8 in the cancer tissue was higher than that in the rectal tissue(P=0.011).The expression of ARHGAP8 was correlated with tumor size(P=0.010)and pathological stage(P=0.005),while it showed no significant association with tumor differentiation degree,lymph node metastasis,liver metastasis,Ki-67,or microsatellite instability expression level.The 44 patients receiving neoadjuvant chemotherapy included 13,8,8,and 15 pa-tients of tumor regression grades 0,1,2,and 3,respectively.Among them,65.91％(29/44)patients showed responses to the treatment.After neoadjuvant chemotherapy,the expression of ARHGAP8 in the cancer tissue was down-regulated in the patients who responded to the chemotherapy(P＜0.001).The response rate in the patients with low protein level of ARHGAP8 was 92.86％,which was higher than that(53.33％)in the patients with high pro-tein level of ARHGAP8(P=0.033).Conclusions ARHGAP8 is highly expressed in the rectal cancer tissue.The pa-tients with locally advanced mid-low rectal cancer and low ARHGAP8 expression are more sensitive to neoadjuvant chemotherapy with the XELOX protocol.ARHGAP8 can serve as a potential biomarker for the occurrence and develop-ment of rectal cancer and an important index for evaluating the efficacy of neoadjuvant chemotherapy with the XELOX protocol in the patients with locally advanced mid-low rectal cancer.