A 47-year-old man has a lung carcinoma with metastases. He receives chemotherapy. A month later, histologic examination of a metastatic lesion shows many foci in which individual tumor cells appear shrunken and deeply eosinophilic. Their nuclei exhibit condensed aggregates of chromatin under the nuclear membrane. The pathologic process affecting these shrunken tumor cells is most likely triggered by release of which of the following substances into the cytosol?
A BCL2
B Catalase
C Cytochrome c
D Lipofuscin
E Phospholipase
Answer - C
This histologic picture is typical of apoptosis produced by chemotherapeutic agents. The release of cytochrome c from the mitochondria is a key step in many forms of apoptosis, and it leads to the activation of caspases. BCL2 is an antiapoptotic protein that prevents cytochrome c release and prevents caspase activation. Catalase is a scavenger of hydrogen peroxide. Lipofuscin is a pigmented residue representing undigested cellular organelles in autophagic vacuoles, much like old clothes in a closet. Phospholipases are activated during necrosis and cause cell membrane damage.
No comments:
Post a Comment