Lung cancer is a leading cause of cancer related deaths worldwide. Currently, over thirty percent of cancer related deaths are attributed to lung cancer. One way to control lung cancer is through chemopreventive intervention with agents that humans could be persuaded to consume. An essential requirement of an ideal chemopreventive agent is that it should be nontoxic, efficacious, easily available and inexpensive. Our laboratory is defining novel chemopreventive agents that humans could consume. The pomegranate (Punica granatum, Punicaceae) fruit has been used forcenturies in ancient cultures for its medicinal purposes. We have shown that pomegranate fruit extract (PFE) possesses remarkable antitumor promoting effects in mouse skin (Int J Cancer 2005;113:423-33) and inhibits prosurvival signaling pathways in human lung carcinoma A549 cells and tumor growth in athymic nude mice (Carcinogenesis 2006; In press). To develop novel mechanism-based preventive approaches for lung cancer, we examined the effect of PFE on growth, progression, angiogenesis and signaling pathways in two mouse lung tumor protocols. Benzo(a)pyrene [B(a)P] and N-nitroso-tris-chloroethylurea (NTCU) were used as carcinogens to induce lung tumors and PFE was given in drinking water (0.2% w/v, equivalent of human consumption of juice derived from two fruits) to A/J mice one week before treatment with carcinogens. Lungtumor yield was examined on 84th day and 140 days after B(a)P dosing and 240 days after NTCU treatment. At 84 days, there were 7.7 tumors/mouse in B(a)P group and 3.5 tumors/ mouse in B(a)P+PFE group, difference = 4.2 tumors/mouse, 95% confidence interval (CI) = -2.6 to 11.0 tumors/mouse, P= 0.2, corresponding to a 53.9% of tumor reduction. At 140 days, B(a)P treated mice had 13.3 tumors/mouse and B(a)P+PFE group had 5.2 tumors/mouse, difference=8.1 tumors/mouse, 95% CI= 5 to 11.4 tumors/mouse, P<0.001, corresponding to a 61.6% of tumor reduction. NTCU treated mice had 17.7 tumors/mouse and mice given NTCU+PFE had 6.1 tumors/mouse, difference=11.6 tumors/mouse, 95% CI=8.9 to 14.3 tumors/mouse, P<0.001, corresponding to a 65.9% of tumor reduction at 240 days. Immunoblot analysis and immunohistochemistry were used to determine effect on cell survival pathways and markers of cellular proliferation and angiogenesis. PFE treatment caused inhibition of (i) activation of NF-κB/p65 and IKKα, (ii) degradation and phosphorylation of IκBα, (iii) phosphorylation of MAPKs, (iv) activation of PI3K and phosphorylation of Akt, (v) activation of mTOR signaling, (vi) phosphorylation of c-met, and (vii) markers of cellular proliferation (Ki-67 and PCNA) and angiogenesis (iNOS, CD31 and VEGF) in lungs of B(a)P and NTCU treated mice. Thus, our data demonstrate that PFE significantly inhibits lung tumorigenesis in A/J mice and merits investigation as a chemopreventive agent for human lung cancer.
98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA