Apoptosis — Intrinsic and Extrinsic Pathways

A 58-year-old man with a 10-year history of chronic hepatitis C virus (HCV) infection develops hepatocellular carcinoma (HCC). A liver biopsy shows extensive hepatocyte apoptosis in the cirrhotic parenchyma, with immunohistochemistry revealing strong cytoplasmic expression of Bcl-2 and Bcl-xL in the malignant hepatocytes, but low expression of pro-apoptotic Bax. Electron microscopy shows intact mitochondrial membranes in many apoptotic cells, with caspase-3 activation evident in the cytoplasm. Which molecular mechanism best explains the resistance of these HCC cells to apoptosis?

A 38-year-old man with chronic lymphocytic leukaemia (CLL) is treated with rituximab, a monoclonal antibody against CD20 on B lymphocytes. Within 48 hours, a marked reduction in circulating B cells is observed. Flow cytometry shows increased annexin V positivity in the remaining CLL cells. Which pathway of apoptosis is primarily responsible for rituximab-induced cell death in this patient?

A 42-year-old woman with newly diagnosed acute myeloid leukaemia (AML) is started on chemotherapy with daunorubicin and cytarabine. After 5 days of therapy, peripheral blood shows a marked reduction in blast cells. A bone marrow biopsy reveals numerous apoptotic bodies within myeloid precursors. Which of the following best explains the mechanism of chemotherapy-induced apoptosis in these leukaemic cells?

A 52-year-old man with newly diagnosed acute myeloid leukemia (AML) is started on chemotherapy. A bone marrow aspirate is performed 48 hours after the first dose. Morphologically, numerous leukemic blasts show cell shrinkage, chromatin condensation, and fragmentation into membrane-bound apoptotic bodies. Which investigation would be most specific to confirm intrinsic (mitochondrial) pathway apoptosis in these cells?

All of the following are correct regarding the regulation of apoptosis EXCEPT: