A correlation study of the expression of HA-CD44st and HER-2 in breast cancer

Negative regulation of CD44st by miR-138-5p affects the invasive ability of breast cancer cells and patient prognosis after breast cancer surgery

OBJECTIVE

To investigate how the negative regulation of CD44st by miR-138-5p affects the invasive ability of breast cancer cell lines and prognosis in postoperative breast cancer patients.

METHODS

RT-PCR, qRT-PCR, and western blot assays were used to detect the expression of CD44s, CD44v6, and CD44st at both mRNA and protein levels. The expression of miR-138-5p in breast cancer cell lines was also evaluated. The binding ability of miR-138-5p to CD44st was determined via a dual-luciferase assay. The CD44 protein expression in breast cancer tissues was detected using immunohistochemistry. A Transwell assay was used to detect the invasive ability of tumor cells. The correlation between CD44st and miR-138-5p mRNA expression in breast cancer tissues was evaluated using qRT-PCR, and the relationship between clinicopathological features was statistically analyzed.

RESULTS

CD44s and CD44v6 were highly expressed in MDAMB-231 cell line, while CD44st was highly expressed in MCF-7/Adr and Skbr-3 cells. None of the CD44 isoforms were expressed in MCF-7 cells. The miR-138-5p was highly expressed in MCF-7 cells, but not in MCF-7/Adr, Skbr-3, and MDAMB-231 cells. The dual-luciferase assay suggested that miR-138-5p could bind to wild-type CD44st 3'-UTR, miR-138-5p overexpression significantly inhibited the expression level of CD44 protein in MCF-7/Adr cells, and miR-138-5p + CD44st (3'-UTR)-treated MCF-7/Adr and Skbr-3 cells were significantly less invasive than those in the control group (P < 0.05). RT-PCR results for 80 postoperative breast cancer patients showed that the mRNA expression rate for CD44st was higher in cancer tissues than in paracancerous tissues, and the expression rate of miR-138-5p was higher in paracancerous tissues than in cancerous tissues (P < 0.01). In cancer tissues, CD44st was negatively correlated with miR-138-5p expression, with correlation coefficient r = -0.76 (Pearson's correlation), coefficient of determination R2 = 0.573, F = 106.89, and P < 0.001. The median overall survival value for patients in the low miR-138-5p expression group was 40.39 months [95% confidence interval (CI): 35.59-45.18 months] and 56.30 months (95% CI: 54.38-58.21 months) for patients in the high-expression group, with a log rank (Mantel-Cox) of 13.120, one degree of freedom, and P < 0.001.

CONCLUSION

In breast cancer cell lines, miR-138-5p negatively regulated expression of CD44st and affected the invasive ability of tumor cells and patient prognosis after breast cancer surgery.

Pleiotropic Roles of ABC Transporters in Breast Cancer

Chemotherapeutics are the mainstay treatment for metastatic breast cancers. However, the chemotherapeutic failure caused by multidrug resistance (MDR) remains a pivotal obstacle to effective chemotherapies of breast cancer. Although in vitro evidence suggests that the overexpression of ATP-Binding Cassette (ABC) transporters confers resistance to cytotoxic and molecularly targeted chemotherapies by reducing the intracellular accumulation of active moieties, the clinical trials that target ABCB1 to reverse drug resistance have been disappointing. Nevertheless, studies indicate that ABC transporters may contribute to breast cancer development and metastasis independent of their efflux function. A broader and more clarified understanding of the functions and roles of ABC transporters in breast cancer biology will potentially contribute to stratifying patients for precision regimens and promote the development of novel therapies. Herein, we summarise the current knowledge relating to the mechanisms, functions and regulations of ABC transporters, with a focus on the roles of ABC transporters in breast cancer chemoresistance, progression and metastasis.

Effect of CD44st and HER2 expression on the postoperative prognosis of breast cancer patients

Objective

CD44st is a member of the CD44 family; abnormal expression of some CD44 isoforms are closely associated with axillary lymph node metastasis, cancer progression, and patients’ prognosis. The objective of this study is to investigate the correlation between the expression of CD44st and HER2 in breast cancer and the effect on patients’ prognosis.

Methods

Primers were designed to target the CD44st mRNA (Gene Bank No FJ216964) which has been newly identified in a drug-resistant breast cancer cell line. The expression of CD44st and HER2 mRNA and proteins in cancerous and paracancerous tissue of postoperative breast cancer patients was detected and compared. Tissue samples were obtained from 102 cases of invasive ductal carcinoma, 19 cases of intraductal carcinoma, and 11 cases of medullary carcinoma. The correlation between CD44st and HER2 expression and clinical pathological features was examined.

Results

The expression rate of CD44st mRNA and protein in breast cancer tissue was 64.4% (85/132), while HER2 mRNA and protein was expressed in 22.0% (29/106) of the samples. The expression of CD44st and HER2 were low in paracancerous tissue. In breast cancer tissue, the expression rate of HER2 mRNA and protein in the CD44st-positive group was 28.2% (24/85), and 10.6% (5/47) in the CD44st-negative group. This difference was statistically significant (P=0.015). Sequencing analysis showed that the amplified CD44st gene in this study was the same as that which was previously discovered in the drug-resistant breast cancer cell line. A linear correlation was found between the expression of CD44st and HER2 (r=0.972, r2=0.945, F=2,213.51, P<0.001). The expression of CD44st and HER2 was also closely associated with luminal cancer subtypes, lymph node metastasis, and TNM stage (P<0.05), but not associated with age, pathological type, or tumor size (P>0.05). The median overall survival in the CD44st high-expression group was 51.85 months (95% CI: 48.48–55.22), which was significantly shorter than that in the CD44st low-expression group (57.61 months; 95% CI: 55.54–59.68, P=0.032).

Conclusion

CD44st is closely related to the expression of HER2. The expression of CD44st affects patient prognosis and is associated with lymph node metastasis, TNM staging, and molecular subtyping.