Key Protein to Suppress Tumor Growth in Breast Cancer

A type of protein that could suppress the growth of breast cancer tumor has been identified by a research team at the University of Birmingham. The protein called Proline-Rich Homeodomain (PRH) plays a key role in the progression of breast cancer tumors. The research team examined whether PRH can help determine the prognosis for patients with the disease.

Role of Proline-Rich Homeodomain

PRH is a protein that controls and regulates when genes are switched on or off. In past studies, the role of PRH in breast cancer has been poorly discerned.

Dr Padma Sheela Jayaraman, of the University of Birmingham's Institute of Cancer and Genomic Sciences, said, "Public databases show that, in a large number of breast cancer patients with a poor prognosis, the activity of the PRH gene had decreased. However, it was not known whether the amount of PRH protein was also lower in these patients as protein levels had not been recorded."

For the study, the research team used breast cancer tissue removed during biopsy. A special staining process was used on breast cancer tissue to observe the levels and location of PRH proteins in breast cancer cells.

In a small study, the researchers found changes in PRH proteins in tumor cells compared to the normal cells that were consistent with the decreased activity of the PRH gene in the public database.

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In the laboratory, the research team found that when PRH protein levels are reduced in a breast tumor, the cells are able to divide, speeding up the progression of the tumor.

"Moreover, we identified some of the genes which are regulated by PRH and specifically contribute to the increased cell division," said Dr Jayaraman.

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The research team also conducted tests in a tumor model of mammary cancers, increasing PRH levels to observe the effect. They found that high levels of PRH blocked the formation of the tumors. Thus the findings suggest that PRH can block tumor formation in some breast cancers.

“We propose that monitoring PRH protein levels or activity in patients with breast cancer could be particularly important for assessing their prognosis,” said Dr Jayaraman.

Since PRH is known to be important in multiple cell types, the study has important implications for other types of cancer. The research team is now working to investigate the importance of PRH in prostate cancer and cancer of the bile duct, a type of liver cancer.

The study is published in Oncogenesis.

Link Between PRH Protein and Cancer Growth

PRH protein also known as hematopoietically expressed homeobox (HHEX), is an essential transcription factor in the embryonic development and in the adult. Altered expression of the PRH protein is associated with cancers of the breast, liver, thyroid and some types of leukemia. Studies have shown that PRH levels could be useful in cancer prognosis and in the choice of treatment options. Reference

1. Gaston K, Tsitsilianos MA, Wadey K, Jayaraman PS. Misregulation of the proline rich homeodomain (PRH/HHEX) protein in cancer cells and its consequences for tumour growth and invasion. Cell and Bioscience (2016), doi: 10.1186/s13578-016-0077-7

Source-Medindia