Inhibition of JNK Sensitizes Hypoxic Colon Cancer Cells to DNA-Damaging Agents

Purpose: We showed previously that in HT29 colon Cancer cells, modulation of hypoxia-induced stress signaling affects oxaliplatin cytotoxicity. To further study the significance of hypoxia-induced signaling through JNK, we set out to investigate how modulation of kinase activities influences cellular responses of hypoxic colon Cancer cells to cytotoxic drugs.

Experimental design: In a panel of cell lines, we investigated effects of pharmacologic and molecular inhibition of JNK on sensitivity to oxaliplatin, SN-38, and 5-FU. Combination studies for the drugs and JNK Inhibitor CC-401 were carried out in vitro and in vivo.

Results: Hypoxia-induced JNK activation was associated with resistance to oxaliplatin. CC-401 in combination with chemotherapy demonstrates synergism in colon Cancer cell lines, although synergy is not always hypoxia specific. A more detailed analysis focused on HT29 and SW620 (responsive), and HCT116 (nonresponsive) lines. In HT29 and SW620 cells, CC-401 treatment results in greater DNA damage in the sensitive cells. In vivo, potentiation of bevacizumab, oxaliplatin, and the combination by JNK inhibition was confirmed in HT29-derived mouse xenografts, in which tumor growth delay was greater in the presence of CC-401. Finally, stable introduction of a dominant negative JNK1, but not JNK2, construct into HT29 cells rendered them more sensitive to oxaliplatin under hypoxia, suggesting differing input of JNK isoforms in cellular responses to chemotherapy.

Conclusions: These findings demonstrate that signaling through JNK is a determinant of response to therapy in colon Cancer models, and support the testing of JNK inhibition to sensitize colon tumors in the clinic.