The effects of PTPN2 loss on cell signalling and clinical outcome in relation to breast cancer subtype.

Abstract

PURPOSE:

The protein tyrosine phosphatase PTPN2 dephosphorylates several tyrosine kinases in cancer-related signalling pathways and is thought to be a tumour suppressor. As PTPN2 is not frequently studied in breast cancer, we aimed to explore the role of PTPN2 and the effects of its loss in breast cancer.

METHODS:

Protein expression and gene copy number of PTPN2 were analysed in a cohort of pre-menopausal breast cancer patients with immunohistochemistry and droplet digital PCR, respectively. PTPN2 was knocked down in three cell lines, representing different breast cancer subtypes, with siRNA transfection. Several proteins related to PTPN2 were analysed with Western blot.

RESULTS:

Low PTPN2 protein expression was found in 50.2% of the tumours (110/219), gene copy loss in 15.4% (33/214). Low protein expression was associated with a higher relapse rate in patients with Luminal A and HER2-positive tumours, but not triple-negative tumours. In vitro studies further suggested a subtype-specific role of PTPN2. Knockdown of PTPN2 had no effect on the triple-negative cell line, whilst knockdown in MCF7 inhibited phosphorylation of Met and promoted that of Akt. Knockdown in SKBR3 led to increased Met phosphorylation and decreased Erk phosphorylation as well as EGF-mediated STAT3 activation.

CONCLUSION:

We confirm previous studies showing that the PTPN2 protein is lost in half of the breast cancer cases and gene deletion occurs in 15-18% of the cases. Furthermore, the results suggest that the role of PTPN2 is subtype-related and should be further investigated to assess how this could affect breast cancer prognosis and treatment response.

• Authors: Cynthia Veenstra, Elin Karlsson, Sanam Mirwani Mirwani, Bo Nordenskjöld, Tommy Fornander, Gizeh Pérez-Tenorio, Olle Stål
• Journal: Journal of cancer research and clinical oncology (J Cancer Res Clin Oncol) Vol. 145 Issue 7 Pg. 1845-1856 (Jul 2019) ISSN: 1432-1335 [Electronic] Germany
• PMID: 31025094 (Publication Type: Journal Article)

Chemical References

• ERBB2 protein, human
• Receptor, ErbB-2
• PTPN2 protein, human
• Protein Tyrosine Phosphatase, Non-Receptor Type 2

Topics

• Breast Neoplasms (classification, enzymology, genetics, pathology)
• Cell Communication
• Cell Line, Tumor
• Disease-Free Survival
• Female
• Gene Dosage
• Gene Knockdown Techniques
• Humans
• Immunohistochemistry
• MCF-7 Cells
• Prognosis
• Protein Tyrosine Phosphatase, Non-Receptor Type 2 (biosynthesis, deficiency, genetics, metabolism)
• Receptor, ErbB-2 (biosynthesis)
• Triple Negative Breast Neoplasms (classification, enzymology, genetics, pathology)