The primary mechanism of action of most anticancer dugs are known and many induce apoptosis. However, there are large gaps in our knowledge of anticancer drug action, in particular how damage and apoptosis are molecularly linked. Furthermore, cell death does not always follow damage, and cancer cells can survive exposure to cytotoxic drugs through defective apoptosis, other resistance mechanisms, or repair. An understanding of the mechanisms that link damage to response may suggest ways to alter the threshold for cell death to make cancer cells more sensitive to chemotherapeutic drugs. Recently, we have shown that Adriamycin, vinblastine, or etoposide activate c-Jun NH2-terminal protein kinase (JNK), a stress-activated protein kinase, in human KB carcinoma cells. Our hypothesis is that JNK-mediated signaling is a critical component of the stress response to functionally distinct anticancer drugs that might affect outcome by influencing or mediating cell death or cell survival.
In Specific Aim 1, the substrates (transcription factors) and effectors (transcriptional activators) of JNK in response to chemotherapeutic drugs will be determined. This will provide a comprehensive picture of molecular events emanating downstream from JNK that may be critical to the overall response to chemotherapy.
In Specific Aim 2, several approaches (JNK antisense oligonucleotides, JNK phosphatase overexpression, dominant negative inhibitors of SEK1, Jun or ATF-2) will be used to generate human carcinoma cell lines with defective JNK signaling in response to chemotherapeutic drugs.
In Specific Aim 3, the JNK signaling-defective cell lines will be used to explore the mechanistic relationship between JNK activation and apoptotic cell death in response to chemotherapeutic drugs. In particular, it will be determined whether JNK regulates the expression or activity of apoptotic regulators (Bcl-2 family) or apoptotic effects (caspases).
In Specific Aim 4, it will be determined whether JNK plays a role in cell survival through regulation of MDR1 expression. By understanding the role of JNK in the response of carcinoma cells to anticancer drugs, we may be able to develop methods to manipulate this signaling pathway in order to increase drug sensitivity or prevent drug resistance.
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