Malignant melanoma shows high levels of intrinsic drug resistance associated with a highly invasive phenotype. In this study, we investigated the role of the drug transporter P-glycoprotein (Pgp) in the invasion potential of drug-sensitive (M14 WT, Pgp-negative) and drug-resistant (M14 ADR, Pgp-positive) human melanoma cells. Coimmunoprecipitation experiments assessed the association of Pgp with the adhesion molecule CD44 in multidrug resistant (MDR) melanoma cells, compared with parental ones. In MDR cells, the two proteins colocalized in the plasma membrane as visualized by confocal microscopy and immunoelectron microscopy on ultrathin cryosections. MDR melanoma cells displayed a more invasive phenotype compared with parental cells, as demonstrated by quantitative transwell chamber invasion assay. This was accomplished by a different migration strategy adopted by resistant cells ("chain collective") previously described in tumor cells with high metastatic capacity. The Pgp molecule, after stimulation with specific antibodies, appeared to cooperate with CD44, through the activation of ERK1/2 and p38 mitogen-activated protein kinase (MAPK) proteins. This activation led to an increase of metalloproteinase (MMP-2, MMP-3, and MMP-9) mRNAs, and proteolytic activities, which are associated with an increased invasive behavior. RNA interference experiments further demonstrated Pgp involvement in migration and invasion of resistant melanoma cells. A link was identified between MDR transporter Pgp, and MAPK signaling and invasion.

Zoledronic acid (ZOL) has proved activity in bone metastases from prostate cancer through inhibition of mevalonate pathway and of prenylation of intracellular proteins. We have reported that ZOL synergizes with R115777 farnesyltransferase inhibitor (FTI, Zarnestra) in inducing apoptosis and growth inhibition on epidermoid cancer cells. Here, we have studied the effects of the combination of these agents in prostate adenocarcinoma models and, specifically, on androgen-independent (PC3 and DU145) and -dependent (LNCaP) prostate cancer cell lines. We have found that ZOL and R115777 were synergistic in inducing both growth inhibition and apoptosis in prostate adenocarcinoma cells. These effects were paralleled by disruption of Ras-->Erk and Akt survival pathways, consequent decreased phosphorylation of both mitochondrial bcl-2 and bad proteins, and caspase activation. Finally, ZOL/R115777 combination induced cooperative effects also in vivo on tumor growth inhibition of prostate cancer xenografts in nude mice with a significant survival increase. These effects were paralleled by enhanced apoptosis and inactivation of both Erk and Akt. In conclusions, the combination between ZOL and FTI leads to enhanced anti-tumor activity in human prostate adenocarcinoma cells likely through a more efficacious inhibition of ras-dependent survival pathways and consequent bcl-related proteins-dependent apoptosis.

Advanced chemorefractory thymic epithelial tumors still represent a challenge in clinical oncology. A rationale-based therapeutic approach targeting a key pathway should represent the ideal solution in a neoplasm that can over-express Epidermal Growth Factor Receptor (EGFR) in the epithelial component. On the basis of these considerations, two patients with metastatic heavily pretreated disease were evaluated for EGFR expression in the primitive tumor, being considered this data as a basis for an anti EGFR treatment with the monoclonal antibody cetuximab which targets EGFR. A strong EGFR expression was revealed by immunohistochemistry in the two cases considered, thus the patients received cetuximab and reported a partial response as assessed by Computed Tomography (CT), Positron Emission Tomography (PET) and fused PET-CT after three months of therapy. Therefore, both patients are still on therapy. This preliminary experience suggests that cetuximab may be a useful therapeutic choice in advanced pre-treated thymic tumors.

We have analyzed the gene modulation induced by zoledronic acid (ZOL) in androgen-resistant prostate cancer PC3 cells with cDNA microarray platform to identify new molecular targets of ZOL in prostate cancer. The gene coding for cysteine-rich, angiogenic inducer, 61 (CYR61) resulted highly downregulated with a fold change of 5.58. Therefore, we have studied the effects of ZOL on CYR61 protein product, and we have found that CYR61 protein expression was decreased significantly after exposure to ZOL. The effect of ZOL on CYR61 expression was dose and time dependent was due to a reduced transcriptional activity of CYR61 promoter. Moreover, the effects induced by ZOL were paralleled by decreased activation of Ras-Raf-1-and Akt-dependent pathways that was dependent from isoprenylation inhibition, since it was antagonized by the addition of geranylgeraniol. Finally, we have investigated the role of CYR61 in the regulation of growth inhibition and invasion/motility of PC3 cells using a shRNA for CYR61 to downregulate the expression of CYR61 protein. The enhanced inhibition of proliferation and motility/invasion induced by ZOL by S-phase accumulation. In the same experimental conditions, CYR61 protein downregulation potentiated the inactivation of the Ras-dependent proliferation pathway and cell cycle inhibitors p21 and p27 expression. ' 2009 UICC