Figure 2.

Nicotine induces proliferation and invasion in human lung cancer and breast cancer cells. (A) The pro-invasive effects of nicotine require α7-nAChR, Src activity, EGFR and intracellular calcium, in A549 cells as seen in a Boyden Chamber assay. The pro-invasive effects of nicotine were reversed by the general nAChR antagonist hexamethonium, the α7-nAChR antagonists α-bungarotoxin and MAA, the Src inhibitor PP2, calcium channel blocker nifedipine and the EGFR inhibitor Iressa (gefitinib). (B) The α7-nAChR subunit is expressed by multiple human cancer cell lines including breast cancer cell lines MCF-7, MDA-MB-468 and pancreatic cancer cell lines Aspc-1, Panc-1 and CAPAN-2, as examined by RT-PCR. RT-PCR for actin was used as the control. (C) BrdU assays show that nicotine induces dose-dependent proliferation of human breast cancer cell lines MCF-7 and MDA-MB-468, the maximal effect being observed at 1µM. (D) Nicotine promotes invasion of MCF-7 and MDA-MB-468 breast cancer cells at a concentration of 1µM, as measured by Boyden chamber assays. A549 NSCLC cells were used as the positive control for the assay. (E) Nicotine stimulates the anchorage-independent growth of MCF-7 and MDA-MB-468 human breast cancer cells in soft agar assays. MCF-7 and MDA-MB-468 cells treated with 1µM nicotine formed larger colonies in soft agar relative to untreated controls. (F) Nicotine-mediated invasion of MCF-7 and MDA-MB-468 human breast cancer cells is dependent on Src activity and intracellular calcium pathways. The pro-invasive effects on nicotine in these breast cancer cells were mediated by both α7-nAChR and DhβE-sensitive nAChRs.