Expression of caspases-3, -6 and -8 and their relation to apoptosis in non-small cell lung carcinoma

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Abstract
We analyzed a set of 103 non‐small cell lung carcinomas (NSCLCs) for caspase‐3, ‐6 and ‐8 expression and apoptosis. Additionally, the expression of bcl‐2, bax and p53 were studied. Caspase‐3 positivity appeared as diffuse, cytoplasmic staining and was restricted to the tumor area. In contrast, the immunoreactivity for caspase‐6 was intense, granular and mostly located in single cells or groups of tumor cells showing apoptotic morphology. The caspase‐8 expression pattern was a combination of the two other caspases studied, featuring both diffuse and single‐cell patterns restricted to the tumor area. No significant differences were seen in caspase ‐3, ‐6 and ‐8 expression between tumors of different histological types or grades. The number of apoptotic cells and bodies was significantly higher in NSCLCs, in which caspase‐8 immunostaining was mainly seen in single cells (p = 0.017), whereas caspase ‐3 and ‐6 expression had no association with apoptosis. It is apparent that, in lung tissue, up‐regulation of caspase expression is a phenomenon associated solely with neoplasia and reflects the readiness of the tumor cells to undergo apoptosis. Interestingly, caspases ‐3, ‐6 and ‐8 each have an individual staining pattern in NSCLC, perhaps reflecting their different position in the caspase hierarchy.