Analysis Of Prognostic Factors And Construction Of Prognostic Model In Breast Cancer With Low HER2 Expression

Objectives:Breast cancer has the highest incidence of female malignant tumors worldwide.HER2 is a driver gene of breast cancer and an independent prognostic factor.Historically,breast cancers were classified as HER2-positive or HER2-negative on the basis of human epidermal growth factor receptor 2(HER2)expression.The introduction of a new antibody-drug conjugate(ADC)has broken the traditional perception that only HER2-positive breast cancer can benefit from anti-HER2 therapy,and marked that HER2 low expression has become a new therapeutic classification.However,low HER2 expression is relatively novel in the diagnosis and treatment of breast cancer.On the one hand,it is still controversial whether there are different prognostic characteristics between HER2 low expression and HER2 0 expression breast cancer.On the other hand,there is a lack of clinical research on prognostic markers for HER2-low expression breast cancer,and new prognostic markers are urgently needed to guide the prognosis stratification of HER2-low expression breast cancer and individualized medicine.As a highly heterogeneous disease,the prognosis of HER2-low breast cancer depends not only on the biological characteristics of tumor cells,but also on the tumor immune microenvironment(TIME).M2 macrophages are highly infiltrated in breast cancer,which is an independent risk factor for Overall survival(OS)in HER2-positive and TNBC patients.Therefore,the prognostic model based on M2 macrophage-related genes is a useful supplement to the current traditional prognostic markers.However,no relevant studies have addressed the new classification of HER2-low breast cancer.Therefore,the aim of this study is to explore the prognostic difference between HER2 low expression and HER2 0 expression breast cancer,and then to explore the prognostic factors affecting HER2 low expression.Finally,a prognostic model of breast cancer patients with low HER2 expression is established from the level of M2macrophage-related genes,which is committed to accurate stratification and promoting the realization of personalized medicine.Methods:A total of 1367 patients with HER2-negative advanced breast cancer were retrospectively collected from The First Affiliated Hospital of China Medical University Medical Oncology Department.SPSS was used to perform univariate and multivariate Cox regression analysis on patients with HER2-negative and HER2-low advanced breast cancer,respectively,to explore whether low expression of HER2 is an independent prognostic factor of HER2-negative advanced breast cancer,and to explore the prognostic markers of HER2-negative advanced breast cancer.K-M survival curve was drawn based on Graphpad Prism software to verify the predictive effect of prognostic markers on prognosis。The gene sequencing data and clinical data of HER2 low expression breast Cancer were downloaded from The Cancer Genome Atlas(TCGA)database.The Relative proportions of 22 kinds of infiltrating immune cells in each tumor tissue were calculated based on CIBERSORT(Cell-type Identification By Estimating Relative Subsets of RNA Transcription).Univariate Cox regression analysis was performed on the meaningful samples after screening to screen out the immune cells related to the OS of patients.According to the median degree of M2 macrophage infiltration,the patients were divided into high and low M2 macrophage infiltration groups,and the Differentially expressed genes(DEGs)between the two groups were screened.To analyze the biological functions of DEGs,Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)analyses were performed.Univariate Cox,Lasso and multivariate Cox regression analysis were performed on DEGs in turn to screen M2macrophage-related genes affecting the prognosis of HER2 low expression breast cancer,and a prognostic model was constructed accordingly.According to the median risk score,the patients were divided into high and low risk groups,and the survival analysis(K-M)was performed to determine the relationship between the prognostic model and OS and verify it in the Test dataset.Independent prognostic analysis was performed based on univariate and multivariate analysis.According to Estrogen Receptor(ER)status,the patients were divided into ER+ and ER-subtypes and subgroup analysis was performed.Gene Set Enrichment Analysis(GSEA)was used for functional annotation of the high-risk group.In addition,based on Tumor Immune Dysfunction and Exclusion(TIDE),the difference of immunotherapy response rate between high and low risk groups was compared.The characteristics of immune infiltration in high and low risk groups were analyzed based on CIBERSORT.Results:Low HER2 expression is not an independent prognostic factor for patients with HER2-negative advanced breast cancer.In advanced breast cancer patients with low HER2 expression,HR status,HER2 status,the first metastatic site and the number of metastatic lesions affect the survival of patients.M2 macrophages are the immune-infiltrating cells most closely related to the poor prognosis of HER2-low breast cancer.In this study,nine M2 macrophage-associated genes were finally screened and a risk score model was constructed.Risk score =(-2.85968)*C10ORF105 expression + 0.00943*BARX1 expression+0.04920*C7ORF61 expression + 0.00152*SLC44A4 expression + 0.04123*ADTRP expression +(-0.00006)* LTF expression + 0.02958*SLC4A8 expression +0.03729*LEMD1 expression + 0.01316*PEX5L expression.The K-M curve showed a significant reduction in survival in the high-risk group compared to the low-risk group,which was validated in the Test set.Subgroup analysis showed that the risk score model had a good prognostic value regardless of ER status.Univariate and multivariate Cox regression analyses confirmed that prognostic model and age were independent prognostic factors for OS.The TIDE score was significantly higher in the high-risk group than in the low-risk group.Compared with the high-risk group,CD8 +T cells,M1 macrophages,and Follicular helper T cells(Tfh)were highly infiltrated in the low-risk group,and M2 macrophages were poorly infiltrated.High risk group showed high infiltration of M2 macrophages,low infiltration of CD8 +T cells,M1 macrophages and Tfh,and activation of TNFA_SIGNALING_VIA_NFKB signaling pathway.Conclusion:This study is the first to establish a prognostic model for breast cancer with low HER2 expression based on the risk score of M2 macrophage-associated genes.The prognostic value of the model is independent of ER expression,and it can better predict the prognosis and evaluate the characteristics of the immune microenvironment.Conclusions: Low HER2 expression is not an independent prognostic factor for HER2-negative advanced breast cancer.In advanced breast cancer patients with low HER2 expression,HR status,HER2 status,the first metastatic site and the number of metastatic lesions affect the survival of patients.The 9-gene model based on the M2macrophage-associated gene risk score can accurately stratifies HER2 low expression breast cancer,and its predictive value is not affected by estrogen receptor expression,which can better predict the prognosis of patients and evaluate the characteristics of the immune microenvironment.