The site-dependent growth characteristics of a human xenotransplanted basaloid squamous cell carcinoma

Purpose: To improve our understanding of the aggressive behaviour of basaloid squamous cell carcinoma (BSCC) certain biological features related to malignancy were compared in the basaloid and in the squamous cell population of this tumour. Methods: Growth rate, cell population kinetics parameters, ploidy and collagenase activity were measured in BSCC xenotransplanted subcutaneously or into oral submucosa. Results: The basaloid component of BSCC showed a growth advantage in the subcutaneous location and formed a mainly aneuploid population (69.3%) without any sign of invasiveness. However the transplantation of this tumour into the oral submucosa resulted in the reappearance of the squamous carcinoma cell population containing diploid and aneuploid cells in equal proportion. The diploid cells in the tumour growing in the subcutis were in G1 phase, whereas 30% of the diploid and aneuploid cells growing in the oral submucosa were in the growing (S + G2) phases of the cell cycle. The mixed tumour cell population in the oral submucosa produced 92-kDa collagenase IV, indicating a potential to infiltrate surrounding tissues. Conclusions: The biological behaviour of a human oral carcinoma (BSCC) in a xenograft model depends on the site of the transplantation. The agressive malignancy of BSCC may be associated with the capacity of the basaloid cell population to generate squamous cells that are able to produce the 92-kDa type of collagenases in an appropriate microenvironment.