Dominika Rittler1, Marcell Baranyi1, Eszter Molnár1, Tamás Garay2,3, Luca Hegedűs4, István Jalsovszky5, József Tóvári6, József Tímár1, Balázs Hegedűs1,4
12nd Department of Pathology, Semmelweis University, H-1091, Budapest, Hungary
2Pázmány Péter Catholic University Faculty of Information Technology and Bionics, H-1083, Budapest, Hungary
3Oncology Center, Semmelweis University, H-1091, Budapest, Hungary
4Department of Thoracic Surgery, Ruhrlandklinik, University Duisburg-Essen, D-45239, Germany
5Eötvös Loránd University, Faculty of Science, Institute of Chemistry, Department of Organic Chemistry; H-1117, Budapest, Hungary
6Department of Experimental Pharmacology, National Institute of Oncology, H-1122, Budapest, Hungary
Malignant melanoma is the most aggressive skin tumor with high metastatic potential. The oncogenic signaling is at least in part mediated by various small G proteins that require prenylation for proper function. Bisphosphonates can inhibit prenylation and proved to have antitumor effect, such as the clinically approved zoledronic acid (ZA), however its poor bioavailability limits the usage. Of note, novel lipophilic bisphosphonates were developed, among others the zoledronic acid analogue BPH1222, with better physicochemical and pharmacokinetic properties.
Aim of this study was to compare the efficacy of BPH1222 to ZA on human melanoma cell lines in vitro and in a subcutaneous tumor model in vivo.
Eight human melanoma cell lines - carrying BRAF, NRAS, PTEN or neither of these mutations - were used to determine the effect of the inhibitors on cell viability, spheroid and in vivo growth inhibition, cell cycle distribution and protein expression using short term SRB assay, spheroid growth assay, xenograft experiment, image cytometry and western blot, respectively.
Based on 2D viability and 3D spheroid assay results, most of the cell lines showed an increased response to BPH, except for M24met. However, even this cell line became more sensitive to BPH in the in vivo experiment. Cell cycle analysis showed that BPH induced apoptosis more effectively in most of the cell lines. Based on the immunoblot analysis the PI3K pathway may be more important mediator of bisphosphonate induced growth inhibition, as p-Akt and/or p-S6 expression decreased while p-Erk levels did not decrease after treatment.
Our results showed that BPH was more effective than ZA in more complex models, probably due to better bioavailability. We found that the PI3K pathway may has a dominant role in the mediation of growth inhibition but further investigations are warranted to identify the specific molecular effectors.
Doctoral School of Pathological Sciences