Neoplasia USMLE Step 1 Practice Question
A 66-year-old man with metastatic non-small cell lung carcinoma (PD-L1 expression >50% on immunohistochemistry) presents with cough and dyspnea. Vital signs: BP 138/82, HR 92, RR 18, Temp 37.1°C, SpO2 98% on room air. He denies fever or weight loss. The oncologist initiates pembrolizumab, explaining the drug targets tumors evading immune destruction through a specific checkpoint ligand. Which of the following mechanisms is most likely being targeted?
Answer choices
- AOverexpression of C3b on tumor cells
- BDecreased VEGF signaling
- CExpression of PD L1 on tumor cells inhibiting T cell activationCorrect answer
- DActivation of ADAMTS13
- ELoss of histamine release from mast cells
- FUpregulation of CD80 on tumor cells promoting cytotoxic T cell exhaustion
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