A novel quantitative method of pten expression assessment in tumor tissue.

Phosphatase and Tensin Homolog deleted on chromosome 10 (PTEN) gene is one of the most important tumor suppressor genes which is involved in the regulation of many signaling cascades (AKT/PKB and MAPK). Subtle changes in its activity lead to cancer susceptibility or aggressive tumor behaviour. Despite the diversity of mechanisms leading to PTEN inactivation, it is frequently associated with a decreased or complete loss of protein expression. About 20% decrease in PTEN expression could lead to the development of cancer. There have been no objective, quantitative methods of PTEN expression assessment that allow to measure the subtle variations of the protein concentration in a tissue-contextual manner. A new quantitative algorithm of immunostaining evaluation based on combination of color deconvolution and relative chromogen signal intensity was used in the study. The proposed algorithm was implemented in the popular ImageJ image analysis software and positively verified in cancer cell lines and tissue models as well as in the tissue samples of colorectal cancer (CRC) patients. The proposed quantitative method of PTEN expression assessment creates an alternative to currently available subjective methods and forms the basis for inter-case and inter-tissue comparisons. Using the algorithm it would be possible to identify three groups of patients with advanced colorectal cancer which could significantly differ in the overall survival. The research should be continued.