Tissue specimens of
squamous cell carcinoma of the larynx from twenty patients were processed for histological and histopathological characterization. A histochemical study of
alkaline phosphatase (ALP) was carried out using the simultaneous azo coupling method, and biochemical studies were performed using disodium
phenylphosphate as substrate. Full-term, normal placentae were used for comparison. The specific activity of ALP from cancerous laryngeal tissue was 8.9 mKAU/mg
protein compared with 154.7 mKAU/mg
protein in the placenta. The ALP was localized histochemically in
tumor cells (
tumor-specific), blood vessels (vascular) and fibrous tissue (interstitial). The
tumor-specific
phosphatase was sensitive to inhibition by
L-phenylalanine,
L-leucine and to a lesser degree by
L-tryptophan and
levamisole. Placental ALP, on the other hand, was completely inhibited by
levamisole, more resistant to
leucine and more sensitive to
phenylalanine and
tryptophan. Biochemical estimation of ALP in cancerous laryngeal tissue combined with inhibition studies revealed that the
tumor-specific activity of ALP constitutes 15% of the total ALP activity while the major
isoenzyme was the vascular ALP, and around one-third of ALP activity was attributed to the interstitial
enzyme. The characterization and localization of these
isoenzymes are described and compared with that of the placenta. The significance and implications of the above findings are presented.