Abstract
Colorectal carcinoma (CRC) is one of the most common cancers in the world. Preoperative radiation with concurrent chemotherapy and subsequent surgery is the standard treatment for locally advanced rectal cancer. However, the tumor response to preoperative chemoradiotherapy (pCRT) varies significantly. CSCs have been found in many human malignant tumors including rectal cancer. Several markers for CSCs have been proposed in CRC, OCT-4 and CD133 have been the most frequently researched. This study was targeted to evaluate the immunohistochemical expression of stem cell markers OCT-4 & CD133 in rectosigmoid adenocarcinomas and correlate their expressions with the grade, stage, and response of the tumor to CRT. The present study comprised 30 specimens of rectosigmoid adenocarcinoma. The primary antibodies used were: OCT-4 antibody, clone PA5-27438, and CD133 antibody, clone144305. Positive OCT-4 expression was observed in 12/30 cases. A significant relationship was found between OCT-4 expression and tumor stage and sex of the patients. No statistically significant relation was found between OCT-4 expression and age of the patients, tumor grade, lymph node stage, pathological response to CRT, OS, or the expression of CD133. 20/30 cases were positively stained for CD133, no significant correlation between CD133 expression and any of the clinicopathological parameters. OCT-4 was expressed in 40% and CD133 in 66% of rectosigmoid cancers studied, so they might be involved in the development of CRC. New therapeutic perspectives based on the selective targeting of the specific population of cells expressing one of those CSCs. OCT-4 expression might be a bad prognostic indicator in rectosigmoid cancer.
Highlights
Rectal cancer is the third most common cancer after lung and prostate cancers in males and breast and lung cancers in females worldwide [1]
There is a critical need of biomarkers predicting response to preoperative chemoradiotherapy (pCRT) at an early time point, allowing selecting rectal cancer patients who would or would not have a benefit from pCRT, to reduce toxicity associated with ineffective pCRT, and to provide adequate treatment option [7]
A significant positive relationship was found between Octamer 4 (OCT-4) expression and tumor stage (p=0.036) (Table 1)
Summary
Rectal cancer is the third most common cancer after lung and prostate cancers in males and breast and lung cancers in females worldwide [1]. The response to pCRT in locally advanced rectal cancer varies among patients. While ~40% of patients have a partial response (PR) and 8%-20% of patients achieve a pCR at the time of surgery, a subset of tumors (~20%) exhibit resistance to pCRT, demonstrating either progression or only minimal regression to stable disease [6]. These different responses to pCRT are associated with long-term outcomes including disease-free survival (DFS) and 10-year cumulative incidence of distant metastasis. There is a critical need of biomarkers predicting response to pCRT at an early time point, allowing selecting rectal cancer patients who would or would not have a benefit from pCRT, to reduce toxicity associated with ineffective pCRT, and to provide adequate treatment option [7]
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