Acid phosphatase activity in the cytosol fraction of the breast cancer tissue.

Acid phosphatase activity was studied in the cytosol fraction of breast cancer tissue. Serum, plasma, and extracts of leukocyte and platelet were used for reference. The breast cancer tissue fraction had an electrophoretic mobility intermediate to leukocyte-derived bands 2 and 4 and corresponding to the platelet-derived band 3. The enzymes derived from platelet and breast cancer tissue were both inhibited by L-tartrate and showed a similar pattern for preferred substrates. By contrast, the breast cancer tissue-derived enzyme was different from the enzyme fraction responsible for the elevated serum enzyme activity in some patients with disseminated breast cancer. The two fractions could be distinguished by electrophoretic mobility and tartrate sensitivity. These findings substantiate our previous report, which suggested that the fraction responsible for elevated serum enzyme activity in the course of breast cancer is not derived from cancer tissue. It is proposed that the osteolysis, resulting from bone metastases, may be responsible for elevated serum enzyme activity in this disease.