Journal of Stem Cell Research & Therapy

Abstract

Acquisition of Cancer Stem Cell Behaviour Plays a Role in Drug Resistance to Combination Chemotherapy and Prognosis in Head and Neck Cancer

Sindhu Govindan Valiyaveedan, Balaji Ramachandran, Jeyaram Iliaraja, Ravindra DR, Bonney Lee James, Kulsum Safeena, Ramanan Pandian, Gangotri Siddappa, Debashish Das, Nisheena R, Aravindakshan Jayaprakash, Vikram Kekatpure, Wesley Hicks Jr, Moni A Kuriakose and Amritha Suresh

Objective: Head and Neck Squamous Cell Carcinoma (HNSCC) demonstrate an exceptional initial response to induction chemotherapy; nevertheless, loco-regional relapse is widespread and not clearly understood. In this study, we investigated the role of Cancer Stem Cells (CSCs) in mediating chemo resistance using patient cohorts and cell line models.
Methods: Profiling of CSC markers was carried out in primary untreated (Cohort I, N=33) and post treatment recurrent (Cohort II, N=27) HNSCC patients by Quantitative PCR (Q-PCR) and Immunihistochemistry (IHC). The prognostic significance of these markers was assessed by ROC curves and logistic regression analyses. The stem cell related behaviour of the drug resistant TPFR cell lines was assessed by the expression of CSC markers and other properties such as self-renewal, migration and tumorigenicity.
Results: Post-treatment recurrent patients showed an over-expression of CSC markers (CD44, ABCG2 and NOTCH1) compared to the treatment naïve cohort. Additionally, CD44 (p=0.028) and ABCG2 (p=0.019), in combination, were poor prognosticators (AUC 0.76). The resistant cell lines (Hep-2 TPFR and CAL-27 TPFR) were further characterized to delineate the role of CSCs in drug resistance. Analogous to the patients, these cells showed an enrichment of CD44+ cells accompanied by an increased spheroid formation (p<0.005) and migratory capacity (p<0.05). The up regulation of CSC markers (CD133, BMI and NOTCH1) and their resistance-mediating targets such as drug transporters and survival/anti-apoptotic pathways suggested possible causal mechanisms. Furthermore, the higher clonogenic survival in the presence of cisplatin (p<0.05) signifying an increased self-renewal capacity with drug resistance. The Hep-2 TPFR (102 cells) also showed an increased tumorigenicity (2/3; 9.5-fold increase in tumor burden) as compared to the parental (1/3; 6-fold).
Conclusion: Our findings suggest that TPF combination chemotherapy enriches the resident cache of CSCs, ultimately leading to drug resistance. Consequently, in a sub set of patients, these drug resistant CSCs might contribute towards disease relapse/recurrence.