Elevation of erythrocyte zinc- and free protoporphyrins with metastatic spread in cancer patients

A sensitive fluorometric method for the evaluation of erythrocyte levels of zinc-protoporphyrin (ZPP) and free-protoporphyrin (FPP) in diluted whole blood was used to survey patients with carcinomas in different stages of metastatic dissemination. ZPP levels in patients with primary tumor or with no evidence of metastatic disease were not different from those of normal donors. However, significantly higher ZPP levels were found in patients with carcinomas in correlation with evidence of metastatic disease, irrespective of the histological origin of the tumor. FPP levels were elevated in all stages of malignancy but were found 4 times higher than the normal levels in patients with metastatic malignancies. Similar increases in ZPP and FPP were detected in patients with inflammatory processes, suggesting a common effector of erythropoiesis in these pathological conditions and in metastatic diseases. Simultaneous detection of higher than normal ZPP and FPP levels in the blood of cancer patients may serve as an additional marker of metastatic dissemination in patients without clinical evidence of infectious or autoimmune diseases.