Abstract
Angiogenesis is a limiting step for the switch from a dormant to malignant state in tumor progression. During tumor development tumor cells induce profound changes in the surrounding tissue, leading to the formation of an altered tumor microenvironment that is critical in permitting further tumor growth and tumor progression. Retinoblastoma (Rb) and colorectal cancer (CRC) display the complexity of the microenvironment constituted by different cell types and their extracellular matrix.
Here we assessed the efficacy of two synthetic derivates of triterpenoid CDDO, CDDO-Im and CDDO-Me, on endothelial, retinoblastoma and colon cancer cells in order to evaluate their effect on angiogenesis, cancer progression and metastatic dissemination.
We observed that CDDO-Im and CDDO-Me inhibited endothelial cells proliferation, migration and tube-formation, hampering the nuclear translocation of NF-kB and affecting the MAPK pathway. In vivo, in a matrigel sponge assay CDDO-Im interfered with angiogenesis when administrated into the pellets or by intraperitoneal injection.
To assess whether these compounds could successfully impairs neuroectodermal-derived tumor growth, we performed in vitro experiments on Y79 and Weri-Rb1 retinoblastoma cells. We performed MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] and LDH (Lactate Dehydrogenase) assays to evaluate CDDO-Im effect on retinoblastoma cell viability and an Annexin V and 7-Amino-Actinomycin D staining to test apoptosis. We observed that CDDO-Im treatment induced a reduction of cell viability at nanomolar doses and early and late apoptosis at different time points.
In order to overcome the side effects of standard chemotherapy drugs, such as vincristine sulphate, we evaluated if CDDO-Im could be used to lower chemotherapy doses. When we combined non-cytotoxic doses of CDDO-Im with vincristine sulphate we observed that after 72 hours of co-treatment, CDDO-Im was able to accomplish the same antiproliferative effect obtained using double doses of vincristine alone.
We also tested the in vitro anti-tumour activity of CDDO-Me on human adenocarcinoma HT29 cell line. The triterpenoid was used alone or in combination with 5FU (5 Fluorouracil), the major chemotherapeutic agent used for CRC therapy. We performed an MTT assay to evaluate its effect on cell viability, an apoptosis test and an alkaline comet assay to assess the potential genotoxic damage.
Preliminary results demonstrated that CDDO-Me induced an almost immediate inhibitory effect on HT29 cells, reducing cell viability already after 24 hours of treatment at 1000-fold lower concentration then 5FU. When HT29 were co-treated with both CDDO-Me and 5FU, no additive effects were observed. Respect to 5FU, CDDO-Me did not induce apoptosis even after long-term treatment, as well as genotoxicity, suggesting that it is able to block cell growth without exerting toxic effects.
These data suggest that the two synthetic triterpenoid CDDO-Im and CDDO-Me could be promising compounds for cancer treatment, acting both on cancer cells and on endothelial cells that support tumor-associated angiogenesis. Our results open the possibility to use chemopreventive molecules in combination with current chemotherapic drugs, to improve their efficacy without cytotoxicity.
Citation Information: Cancer Prev Res 2011;4(10 Suppl):B76.
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