Datta, Kaustubh

Abstract Regulator of G-protein signaling–GAIP-interacting protein COOH terminus (GIPC) is involved in protein trafficking, endocytosis, and receptor clustering and is associated with insulin-like growth factor I receptor (IGF-IR), a receptor important for proliferation and anchorage-independent growth. Here, we described GIPC expression in different human pancreatic adenocarcinoma (PCA) cell lines and we examined the role of GIPC in the regulation of IGF-IR protein levels in PCA. Interestingly, inhibition of GIPC expression by RNA interference led to reduced IGF-IR protein levels and a subsequent decrease in proliferation of PCA cells. We also determined that the PDZ domain of GIPC is essential for the post-translational regulation and the binding of IGF-IR. The importance of GIPC in pancreatic cancer development and progression is supported by tissue microarray data of 300 pancreatic cancer specimens where GIPC is highly expressed in PCA. Taken together, our data suggest that GIPC is a central molecule for the stability of IGF-IR and could be a target for future therapy. (Cancer Res 2006; 66(21): 10264-8)

Abstract Purpose: The overall 5-year survival of patients with pancreatic cancer remains <5%. Novel therapeutic strategies are needed. We examined the effect of rapamycin, alone and in combination with antiangiogenesis therapy, on pancreatic cancer in vivo. Experimental Design: Human pancreatic cancer AsPC-1 cells were orthotopically injected into severe combined immunodeficient/beige mice to evaluate primary tumor growth and liver metastasis after treatment with rapamycin alone or in combination with anti-vascular endothelial growth factor antibody 2C3. Tumor cell proliferation was determined by bromodeoxyuridine incorporation. To detect tumor cell apoptosis, the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay was used. Tumor angiogenesis was investigated by using a monoclonal anti-CD31 antibody. All statistical tests were two-sided. Results: Rapamycin, alone and in combination with 2C3, strongly inhibited primary and metastatic tumor growth in an orthotopic pancreatic cancer animal model. Furthermore, the combination therapy significantly improved the effect on liver metastasis compared with single treatment with either rapamycin (P = 0.0128) or 2C3 (P = 0.0099). Rapamycin alone inhibited pancreatic tumor cell proliferation, induced apoptosis, and decreased tumor angiogenesis. Nevertheless, the combination therapy showed a significant, stronger inhibition of tumor cell proliferation (P = 0.0002 versus rapamycin alone and P < 0.0001 versus 2C3 alone). The induction of apoptosis was significantly higher than in the rapamycin-treated group (P = 0.0039). Additionally, the combination therapy further improved suppression of tumor cell angiogenesis compared with rapamycin treatment (P = 0.029) Conclusions: Our studies propose new therapeutic strategies to inhibit both primary and metastatic tumor growth in pancreatic cancer. Considering the fact that liver metastasis is a crucial problem in advanced stages of pancreatic cancer, the combination therapy of rapamycin plus anti-vascular endothelial growth factor antibody 2C3 is a significant advantage compared with single treatment with rapamycin.