The dying process and cell viability in squamous cell carcinoma after arterial infusion of methotrexate: A light, ultrastructural, histochemical and enzyme analysis

Two fundamentally different processes of cell death, necrosis and apoptosis, are recognized recently. The nature of cancer cell death and cell kinetics after continuous intra-arterial infusion of methotrexate (MTX) were evaluated in a 47-year old patient with 3 huge, fungating squamous cell carcinoma over left lower limb. Six hours after initiation of external iliac arterial infusion, mitochondria swelling with rupture of internal cristae was the initial morphological changes under electron microscopic observation, followed by cell swelling, destruction of cytoplasmic organelles within 1-2 days, and finally fragmentation of nucleus of cancer cells accompanied by gross tissue inflammation. These morphological changes revealed the necrotic cell death in our case. Cell viability detected by an enzyme-histochemical staining of NADH-diaphorase demonstrated extensive cancer cell death 36 hours after therapy. During the remission period after therapy, residual cancer cells showed NADH-diaphorase positive and PCNA-cyclin negative staining, indicating that these viable cancer cells were in a non-proliferative state. In conclusion, continuous intra-arterial infusion of MTX induces a very rapid necrotic cell death in squamous cell carcinoma. A concurrent toxicity of MTX to the mitochondria may play a crucial role and act synergistically with inhibition of DNA synthesis to provoke cancer cell death.