Usage of the NF-kappaB inhibitor sulfasalazine as sensitizing agent in combined chemotherapy of pancreatic cancer

Abstract

Sulfasalazine is commonly used as an anti inflammatory agent and is known as a potent inhibitor of NF-kappaB. Some pancreatic carcinomas are characterized by a constitutively elevated NF-kappaB activity accounting for chemoresistance. To elucidate whether blockade of NF-kappaB activity with sulfasalazine is suitable for overcoming this chemoresistance in vivo, we employed a mouse model with subcutaneously xenotransplanted human Capan-1 pancreatic carcinoma cells. Fourteen days upon tumor inoculation, animals were randomized in 6 groups, receiving no treatment, treatment with gemcitabine or with etoposide, either alone or in combination with sulfasalazine, or with sulfasalazine alone. Two therapy regimens were given with a 7-day interval in between. Upon treatment with etoposide or gemcitabine alone, tumor sizes were moderately reduced to 65-68% and 50-65%, respectively, as compared to untreated tumors. Sulfasalazine alone only decreased temporarily the tumor sizes. Sulfasalazine in combination with gemcitabine showed only partially higher reduction in tumor sizes than gemcitabine alone, whereas the combination with etoposide reduced significantly the tumor sizes in all experiments (down to 20%). TUNEL-staining showed higher numbers of apoptotic cells in tumors from the combination groups, in particular with etoposide, and proliferation as indicated by Ki67 staining was strongly reduced. Furthermore, combined treatment of sulfasalazine with the cytostatic drugs led to a decreased blood vessel density. Immunohistochemical staining of the activated p65 subunit showed that sulfasalazine treatment abolished the basal NF-kappaB activity in tumor xenografts. These data imply that the well established anti-inflammatory drug sulfasalazine sensitizes pancreatic carcinoma cells to anti cancer drugs, in particular to etoposide in vivo by inhibition of NF-kappaB. This combined chemotherapy offers great potential for improved anti-tumor responses in pancreatic carcinomas.