| Background:Colorectal cancer is one of the most common malignancies in the world and a major cause of cancer-related death.Rectal cancer makes up more than half of intestinal cancer cases in China,and total mesorectal excision followed by Neoadjuvant chemoradiotherapy(nCRT)is the recommended course of treatment for locally advanced rectal cancer(LARC).Only 15%to 20%of LARC patients experience a pathological full response following nCRT,demonstrating the wide variation in individual reactions to nCRT.Overall survival has greatly increased thanks to this combined regimen,but new difficulties are also presented by considerable radiation damage and a low response rate.The mechanism of colorectal cancer’s resistance to radiotherapy and chemotherapy,as well as the possibility for therapeutic change,are major study topics.Poly-cytosine binding proteins(PCBP1),located on chromosome 2,belong to a family of heteroribonucleotides.According to recent research,PCBP1.plays a vital regulatory role in the regulation of tumor progression and is strongly linked to tumor proliferation,the epithelial-mesenchymal transition,and the remodelling of the tumor immunological microenvironment.Therefore,we speculate that in advanced rectal cancer,the expression of PCBP1 may be closely associated with chemoradiotherapy resistance.However,the role of PCBP1 in rectal cancer progression and chemoradiotherapy resistance remains unclear.Methods:We retrospectively collected the formalin-fixed paraffin-embedded tissue of 245 cases of LARC before nCRT treatment.Patients with TRG grades 3-4 were defined as radiotherapy-sensitive and those with TRG grades 0-2 as radiotherapy-resistant.Combined with the TCGA database,the role of PCBP1 in rectal cancer was comprehensively revealed,and the correlation between.PCBP1 and radiotherapy resistance in advanced rectal cancer was explored by immunohistochemistry.In order to further explore the role of PCBP 1 in radiotherapy resistance in colorectal cancer,PCBP1 expression silencing cell lines were constructed,transcriptome sequencing analysis was performed,and in vivo experiments were performed.Results:The results of TCGA showed that CD8+T cells and CD4+ T cells in the sensitive group were significantly higher than those in the resistant group,while CD4+Th2 T cells in the sensitive group were significantly lower than those in the resistant group.We performed CD3 and CD8 immunohistochemistry on the samples collected from patients’ colonoscopies before radiotherapy.The results showed that the number of CD3 and CD8 positive cells was significantly higher in the radiotherapy-sensitive group than in the radiotherapy-resistant group;the results were consistent with the analysis of the common database.We also investigated the expression of PCBP1 in the tumour tissues of both groups of patients.The results showed that PCBP1 expression was significantly higher in the radiotherapy-sensitive group than in the radiotherapy-resistant group;the expression of PCBP1 in normal tissues was higher than that in tumor tissues.The number of CD8-positive cells in the PCBP1 high expression group was significantly higher than that in the PCBP1 low expression group,suggesting that the expression of PCBP1 was positively correlated with the number of CD8-positive cells.Subsequently,we downregulated the expression of PCBP1 in intestinal cancer cells and performed in vivo experiments.The results suggested that the sensitivity of tumors to radiotherapy was significantly decreased after the expression of PCBP1 was decreased.Conclusion:Decreased expression of PCBP1 was associated with poor prognosis and insensitivity to NCRT in advanced rectal cancer,while PCBP1 expression was closely associated with CD8 T cells in advanced rectal cancer receiving radiotherapy.Background:Cancer survivors show an increased risk of developing a second primary malignancy(SPM)after radiation therapy(RT).Data on the association between RT and SPM are limited.Radiation therapy is a common treatment option for pelvic cancer patients,which could induce the development of second primary radiation-exposed rectal cancer(SC).However,compared with primary rectal cancer(PC),the molecular characteristics and immune micro-environmental status of radiation-induced rectal cancer are still not reported.Methods:This is a pan-cancer cohort study using data from Surveillance,Epidemiology and End Results registries between January 1973 and December 2015.Multivariable COX and Fine&Gray’s competing risk regression was used to evaluate the hazard ratio(HR)and 95%confidence interval(CI)of SPMs in patients undergoing RT compared with those undergoing No-RT(NRT).Poisson regression was used to evaluate the RT-associated risks(RR)and the standardized incidence ratio(SIR)for SPMs.Based on 16,334 single-cell RNA(scRNA)transcriptome from the rectum tissues of four individuals with SCs and PCs,we first estimated the distinct epithelial cancer cells and specific immune micro-environment of SCs.Additionally,immunohistochemistry on large number of tumors was used to validate the corresponding results.Results:24 types of risk increased SPM(RI-SPMs)were identified,including malignancies of oropharynx,hypopharynx,larynx,esophagus,lung,breast,liver,pancreas,stomach,colon,rectum,ovary,corpus uteri,ureter,vagina,urinary bladder,penis,testis,kidney and so on.The cumulative incidences of RI-SPMs were higher compared with those undergoing NRT(19.8%vs 15.3%,P<0.001).The onset trends of RRs for RI-SPMs decreased with increasing age at FPM diagnosis(aged 20-49 years:RR,1.52;aged 50-69 years:RR,1.31;aged 70 years:RR,1.21),and increased with increasing latency since FPM diagnosis(60-119 months:RR,1.28;120-239 months:RR,1.24;240-360 months:RR,1.46).The 10-year overall survival of RI-SPMs was significantly lower than matched patients undergoing NRT(28.5%vs 31.7%;P<0.001).Across the ten major cell types from rectum tissues,the strongest SC-associated changes appeared in sub-epithelial population with higher copy number variation and the subsequent enhancement of MYC oncogene.The distinct immune micro-environment was charactered by the enhancement of Treg CD4 T cells,and accumulation of neutrophil.Notably,we found that CXCL13 marked CD8 T cells in PCs but decreased in SCs.Conclusions:RI-SPMs deserve more attention considering their time-cumulative onset risk and poor prognosis.Long-term surveillance is necessary for cancer survivors treated with RT.Our findings support a distinct tumorigenesis and immune micro-environment between PCs and SC,further providing new insights into the cellular architecture of SC and help develop novel diagnostic and therapeutic approaches for SC. |
PDF Full Text Request