Abstract 3881: The expression of CD98hc might be a marker of radiation resistance in HNSCC

Introduction: Head and Neck squamous cell carcinoma(HNSCC) represents an aggressive malignancy. Although new advanced therapeutic strategies have been applied to date, the 5-year survival rate have not been considerably improved. Generally speaking, high radio-sensitive HNSCC has good prognosis, however, there are radio-resistant HNSCC. Recently, Sanne et al, have reported CD98 is one of the marker of Cancer Stem Cell. Moreover, the over expression of CD98hc is high associated with different cancers including the colon cancer, renal cancer. CD98 is heterodimeric protein that comprises a heavy chain and a light chain. The CD98 heavy chain is type 2 linkage to one of 6 amino acid transporters. We hypothesize that irradiation may contribute to overexpression of CD98hc and expansion Cancer Stem Cell population in HNSCC. Methods:cell culture: Ho-1-u-1(Mouth floor), Sa3(Gingiva), HSC2, HSC3,HSC4(tongue) were used for this experiment. These cell lines were exposed to 60 Gy (2Gy/day) to establish stable cell lines to radiation.Flow cytometry: For analysis of CD98-positive fraction, cell pellets were incubated with FITC-conjugated anti-human CD98hc mAb at the dilution of 1:11 at 4°C for 15min.Sphere formation assay: Cells were cultured in a serum-free medium. 1x104 cells were seeded in 80μl of serum free RPMI1640 medium. The recipe of which was mentioned above. Containing 1.0% agar on 100μl of a solidified serum free RPMI1640 was poured on the top of each well. The cells were incubated for 20 days in the same atomosphere as that for the monolayer culture.Migration Assay: Radius 24 well Cell Migration (Cell Biolabs, INC.) were purchased. The experiment was conducted according to the decided plotocol. Result: In radiation resistant cells, spindle-shaped and large cytoplasmic cells were founded. After irradiation, the expression of CD98hc increased in all cell lines. In Ho-1-u-1, the population was divided into two distinct subpopulations showing a higher and a lower expression of CD98hc. Irradiated cancer cells exhibit an efficient ability to developed numerous large sphere. Irradiation had enhanced self-renewal of Cancer Stem Cells. Cell motility was higher in radio-resistant cells than their parental cells. Conclusion: Radio-resistant cells overexpressed CD98hc. In other words, CD98hc may be a marker of radiation resistance. Since incomplete radiation therapy can expand Cancer Stem Cell population, so elucidation of mechanism of radiation resistance will improved r