Differences in in vitro photodynamic sensitivity among head and neck cancers.

This study was conducted to address the question of how cancers of different histologies of the head and neck region responded to photodynamic therapy (PDT). Five human cancer cell lines were investigated: two squamous cell carcinoma lines (pharynx and tongue), mucoepidermoid carcinoma (submaxillary gland), rhabdomyosarcoma (embryonic) and adenocarcinoma (colon). The cell lines were treated with haematoporphyrin derivative (HpD) at doses of 0.78-25Mug ml(-1), with excitation of the absorbed drug by a 'black light' source (340-380 nm). An MTT assay demonstrated different PDT responses among the various cell types. On the basis of LD(50), the sensitivity of the different cell lines was ranked as follows: adenocarcinoma> squamous cell carcinoma> rhabdomyosarcoma> mucoepidermoid carcinoma. The magnitude of the LD(50) was suggested by a drug uptake study to be governed in part by cellular levels of sensitizer and in part by intrinsic cell sensitivity. This study provided information that may help to identify the histological types of head and neck cancers that would respond favourably to PDT.