The Expressions Of PTP1B And ER-α36 In Breast Cancer And Its Clinicopathology Significance

Breast cancer is the most common malignant tumors of women, which is highly heterogeneous, resulting in differences of clinical behavior, sensitivity to therapy and prognosis in different patients. Recent years, different molecular subtypes were identified in breast cancer bringing a new prespective to guide individual treatment and predict prognosis.Invasion and metastasis are the major causes of recurrence and poor prognosis of breast cancer, and remain the major problem to overcome. Recent studies showed that cancer stem cells(CSCs) play an important part in promoting tumor invasion and metastasis. CSCs are a very rare subpopulation in tumor cells, which can self-renew, infinite proliferous, multiple differenciate and resconstruct the tumor. Our previous study indicated that ER-α36 positive breast cancer cells were ALDH1 positive and exhibited stem cell-like properties. Epithelial-mesenchymal transition(EMT) is another important mechanism that promoting tumor cells metastasizing. Besides, the invasion of tumor cells needs to degradate the extracellular matrix, in which the matrix metalloproteinase(MMPs) are the key proteins. Studies showed that the invasion and metastasis potential are different in different molecular subtypes of breast cancer, but the potential mechanisms is still unclear.Protein tyrosine phosphatase 1B(PTP1B) is a non-transmembrane protein tyrosine kinase, which has been observed to be highly expressed in tumors including gastric carcinoma, colorectal cancer, prostatic cancer, etc. In breast cancer, the expression pattern of PTP1 B in different subtypes and whether PTP1 B influence invasion and metastasis of tumor cells are still unknown. Based on these, we first identified the molecular subtypes of 328 cases of breast cancer, and then analyzed the correlation of PTP1 B expressions and clinical-pathological parameters of breast cancer patients. Next, we explored whether PTP1 B affect breast tumor cells invasion and metastasis by PTP1 B knockdown or overexpression. Then, we investigated the mechanism of PTP1 B regulating breast cancer cell invasion and metastasis. Finally, explored the expression of PTP1 B and ER-α36 in different subtypes and analyzed the clinicopathology significance.Results and conclusions are listed below:1. Identification molecular subtypes of breast cancer(1) Using ICC and RT-PCR, ER, PR and HER2 expressions at protein and m RNA levels were detected. Based on the results, 12 breast cancer cell lines and normal breast cell lines were divided into four subtypes. MCF7 and T47 D were identified as Luminal A subtype(ER+ and/or PR+, HER2-). BT-474 and UACC-732 were Luminal B subtype(ER+ and/or PR+, HER2+). MCF10 A, MDA-MB-231, MDA-MB-453, BT549, SUM159 and Bcap37 were Basal-like subtype(ER-, PR-, HER2-). SKBR3 and JIMT1 were HER2 overexpression subtype(ER-, PR-, HER2+).(2) Using IHC staining, we detected ER, PR, HER2 and Ki67 in 328 cases of invasive breast cancer. We identified that 151 cases are Luminal A subtype, 54 cases are Luminal B subtype, 94 cases are Basal-like subtype and 29 cases are HER2 overexpression subtype. Overall survival(OS) and disease-free survival(DFS) were all significantly different in different subtypes(P<0.001). Among them, the OS and DFS were all significantly longer of Luminal A subtype than those of any other subtypes(P<0.001).2. PTP1 B promotes invasion and metastasis of breast cancer cells(1) PTP1 B expression in breast cancer was significantly higher than normal tissue(P<0.001), which is expressed in cytoplasm of cells.(2) Higher expression of PTP1 B was positively associated with lymph node metastasis in breast cancer patients(P<0.01).(3) Knockdown of PTP1 B in MCF7 cells could reduce the invasive and migratory capacities(P<0.01).(4) Over-expression of PTP1 B in MDA-MB-231 cells could promote the invasive and migratory capacities(P<0.01).3. PTP1 B regulated invasive and migratory capacities through PTEN and MMPs.(1) PTP1 B knockdown in MCF7 cells could sufficiently reduce the AKT activity via upregulating PTEN activity. However, forced expression of PTP1 B significantly increase AKT phosphorylation by reduceing PTEN activity.(2) PTP1 B knockdown in MCF7 cells could sufficiently suppress the expression of MMP2 and MMP7, while PTP1 B overexpression promote the expression of MMP2 and MMP7.(3) PTP1 B knockdown in MCF7 and overexpression in MDA-MB-231 cells did not result in expression changes of OCT4, NANOG, SOX2 and ALDH1(P>0.05). We also generated spheres of MCF7 and MDA-MB-231 cells, and found that PTP1 B expressions were not changed.(4) PTP1 B knockdown or overexpressin in MCF7 cells did not affected expressions of E-cadherin, N-cadherin and Vimentin(P>0.05).4. High expression of PTP1 B was associated with worse prognosis of Luminal subtype breast cancer.(1) PTP1 B expression varies in different subtypes of breast cancer and cell lines. The expression was higher in Luminal and HER2 overexpression subtypes, and was lower in Basal-like subtype(P<0.05).(2) Higher PTP1 B expression was positively associated with ER expression(P<0.05).(3) Higher PTP1 B expression was associated with poor prognosis of Luminal subtype of breast cancer(P<0.05, DFS), and was not associated with prognosis of other subtypes.5. The significance of ER-α36 in breast cancer tissues.(1) Higher expression of ER-α36 was positively associated with lymph node metastasis(P<0.05) and related to poor prognosis in breast cancer patients(P<0.05).(1) ER-α36 expression varies in different subtypes of breast cancer tissues. The expression was higher in Luminal and HER2 overexpression subtypes, and was lower in Basal-like subtype(P<0.05).In conclusion, identification of molecular subtypes of breast cancers may help designation of individual treatment and identification prognosis. In addition, PTP1 B and ER-α36 were highly expressed in breast cancer, and positively associated with LNM. PTP1 B promoted breast cancer cell invasion and metastasis via PI3K/AKT pathway and MMPs, but not CSC and EMT-related pathways. These results helped us to understanding characters of molecular subtypes and the potential metastasis mechanisms of breast cancers.