A clinical study of hypoxia and metallothionein protein expression in squamous cell carcinomas

The objective was to discover whether the oxygen-regulated protein, metallo thionein, is expressed in the hypoxic cells of squamous cell carcinomas, Tw enty patients with squamous cell carcinoma of the uterine cervix or head an d neck were infused with a solution of the hypoxia marker, pimonidazole hyd rochloride, at a dose of 0.5 g/m(2). The following day, biopsies were colle cted, formalin fixed, paraffin embedded, and sectioned at 4 mu m. Sections from each biopsy were immunostained for pimonidazole binding, metallothione ins I and II, involucrin, and proliferating cell nuclear antigen. A total o f 84 biopsies were analyzed. Sixty-four of 84 biopsy sections contained hyp oxia, Of the hypoxia-containing sections, 43 of 64 or 67% showed no microre gional overlap between hypoxia and metallothionein; 7 of 64 showed overlap; and 14 of 64 showed a combination of overlap and no overlap. On a tumor-by -tumor basis, 5 of 7 head and neck and 7 of 13 cervix tumors showed no over lap between metallothionein and hypoxia at the microregional level. Ranges for the percentage of the area of hypoxia in head and neck (<0.9 to 17%) an d cervix (<0.1 to 14%) tumors were similar. In the hypoxia-containing secti ons, immunostaining for involucrin, a molecular marker for differentiation, overlapped with that for hypoxia in 82% of the cases. The majority of hypo xic cells in squamous cell carcinomas do not express metallothionein protei n, although metallothionein is induced by hypoxia in human tumor cells in v itro. Hypoxic cells in human tumors tend to be in regions immunostaining fo r involucrin, and it seems possible that differentiation of hypoxic cells i n squamous cell carcinomas might affect metallothionein I and II expression .