engleski

SOX2 CANNOT BE USED AS A PREDICTIVE MARKER FOR RADIORESISTANCE OF COLORECTAL CANCER

Neoadjuvant long course chemoradiotherapy (LCCRT) in patients with locally advanced rectal cancer reduces the tumour mass and local recurrence, downstages the pathologic extent of the tumor and enables sphincter preservation surgery. Patients treated with LCCRT but have tumors resistant to such therapy have prolonged waiting time to surgical resection without adequate therapy, which can lead to tumor progression during that period. Selection of markers that can predict tumor radiosensitivity is necessary. There are several known mechanisms of radioresistance, and generation of cancer stem cells (CSC) is one of them2. CSC has self-renewal ability and multilineage diff erentiation potential, and is more resistant to various therapeutic treatments. SOX2 was recently recognized as a gene associated with CSC and epithelial-mesenchymal transition that promotes resistance to chemotherapy in ovarian cancer. The research was conducted on the assumption that the determination of SOX2 in samples before the neoadjuvant chemoradiotherapy could predict tumor resistance to therapy. We evaluated the immunohistochemical expression of SOX2 protein in 62 colorectal carcinoma samples taken from a biopsy before LCCRT (Group 1) and matched samples after LCCRT (Group 2). We did not fi nd a signifi cant diff erence in SOX2 expression between groups (33.9% vs. 41.8%) (χ2=0.78 ; P=0.376). Twenty-one patients had good pathological response to LCCRT and only 19% of tumors showed SOX2 nuclear staining while tumors with poor pathological response to therapy expressed SOX2 in 46.3% of cases (χ2=4.43 ; P=0.035). Of the 22 patients who demonstrated progression of the disease after LCCRT and surgery, SOX2 was positive in 59% of tumors compared to 25% of SOX2 positive tumors in patients without disease progression (χ2=7.07 ; P=0.008). We noticed a discrepancy in SOX2 expression between groups. Thirteen tumors gained SOX2 expression after LCCRT compared to match samples before LCCRT whereas eleven tumors lost the SOX2 expression after chemoradiotherapy. Based on our results, nuclear staining of SOX2 is in correlation with poor response to therapy and worse prognosis but cannot be used as predictive marker of radioresistance of the colorectal cancer.

SOX2, colorectal cancer, neoadjuvant chemoradiotherapy

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