Receptor-type Protein tyrosine phosphatase Receptor Type U (PTPRU) is a member of the protein tyrosine phosphatase (PTP) family, a family known to have roles in regulating cell growth, cell adhesion and differentiation. PTPRU has been shown to have a possible impact on focal adhesion complex and may interact with the cell adhesion regulator CTNNB1 (-catenin). It has been shown to influence the development of bone and central nerve system (CNS). However, little is known for the role of PTPRU in cancer and particularly in clinical cancers. The present study investigated the expression pattern of PTPRU and its clinical significance in clinical breast cancer.

Expression levels of PTPRU in a cohort breast cancer tissues including normal and tumour tissues were tested by way of transcript analysis. Patient’s clinical, pathological, hormone receptor status, molecular subtypes and clinical outcomes (with a 10 year followup) were analysed against PTPRU expression.

Breast cancer tissues had a marginally increased expression of the PTPRU transcript (p=0.081) compared with normal mammary tissues. There was a marked reduction of PTPRU transcripts in breast tumours which developed local recurrence (p=0.022, compared with those who remained disease free). ER positive (ER+) tumours had a significantly higher PTPRU than ER negative (ER-) tumours (p=0049). PGR negative tumours also had raised levels compared with PGR negative tumours (p=0.0106). Patients who had high levels of PTPRU had a significantly longer disease free survival (DFS) than those with low levels (p=0.046) and also have a longer overall survival (OS) although this was yet to be statistically significant (p=0.056). The connection between PTPRU and DFS was more prominent in Her3 positive tumours (p=0.039). In the Her2(+)/ER(-) molecular subtype, high levels of PTPRU were associated with both longer DFS and OS. Interestingly, PTPRU does not show a correlation with CTNNB1 (a-catenin) in cancer tissues (r=0.111, p=0.291), but significantly correlated with E-cadherin (r=0.289, p=0.005) and a-catenin (r=0.208, p=0.046).

The expression of Protein tyrosine phosphatase receptor type U (PTPRU) has a significant correlation with favourable clinical outcome of patients with breast cancer, a relationship with a strong connection with the ER status of cancer cells. PTPRU thus has a hallmark of being a tumour suppressor in breast cancer and warrant further investigation for its prognostic values in breast cancer.