Objectives: Cancer stem cells are involved in radioresistant cancers. Transcription factors Sry-related HMG box (SOX2) and octamer binding transcription factor 4 (OCT4) can confer pluripotent cell characteristics and self-renewal ability and are involved in carcinogenesis, metastasis, tumor recurrence, and resistance to therapy. Apoptosis, DNA repair, and telomerase factors also contribute to radioresistance. We sought to identify the role of SOX2 and OCT4 as cancer stem cell markers and their effects on apoptosis (via caspase 3), DNA repair (Chk1) and telomerase (hTERT) in conferring resistance to radiotherapy.
Methods: We conducted a case-control study of 40 patients with stage IIIB cervical squamous cell carcinoma who completed radiation therapy at Cipto Mangunkusumo Hospital, Jakarta, Indonesia. The patients were classified according to their treatment response as having exhibited a complete or incomplete response. Clinical follow-up and Pap smears were performed between six and 12 months after therapy for those with a good initial response to determine the final response to therapy. Immunohistochemistry was used to analyze SOX2, OCT4, caspase-3, Chk1, and hTERT expression in paraffin sections of the initial biopsy.
Results: Strong expression of SOX2 (p = 0.011, p = 0.001) and OCT4 (p < 0.001, p < 0.001) was significantly associated with both an incomplete initial and final therapy response, respectively. Multivariate analysis showed that SOX2 and OCT4 expression levels were the strongest markers of an incomplete response to radiotherapy (odds ratio (OR) = 5.12, p = 0.034, and OR = 17.03, p = 0.004, respectively).
Conclusions: Strong expression of SOX2 and OCT4 may be a good indicator of incomplete radiotherapy outcome in patients with stage IIIB cervical cancer.
Keywords: Cancer Stem Cells; Cervical Cancer; Oct-4 Transcription Factor; Radiation Tolerance; SOXB1 Transcription Factors.