Suchandrima Saha, Monisankar Ghosh and Samir Kumar Dutta find out a potent tumoricidal co-drug ‘Bet-CA’ – an ester derivative of betulinic acid and dichloroacetate selectively and synergistically kills cancer cells.
In this study they accentuated the effect Bet-CA deliberates on cancer cells and furthermore the molecular mechanisms by which it induces cell death. It potently inhibits proliferation and induces apoptosis on a wide spectrum of cell lines. Equally importantly, applying discreet yet novel experimental designs they confer Bet-CA spares normal fibroblasts and additional data produced promising evidence for the fact that Bet-CA is purportedly a non toxic compound. Thus, the theme emerging from the studies is that Bet-CA selectively targets the neoplastic cells and impairs their survival and proliferation.
Cellular uptake studies were performed to document the proposed postulation regarding the cleavage of Bet-CA by intracellular esterase. Astoundingly it was noted that Bet-CA being an ester derivative can bypass the barriers of extracellular breakdown, offer itself for cleavage by cellular esterases to present a prominent damage to the malignant variety. Therefore it can be convincingly claimed that Bet-CA is fortuitously endowed with the potential to escape non-specific degradation and synergistically act for benefit.
Suppressed glucose oxidation/glycolysis ratio, mitochondrial hyperpolarization and increased levels of handling stress contribute to the resistance of apoptosis. As cancer cells already have elevated levels of intrinsic ROS it is quite apparent that these malignant cells will become vulnerable when exposed to further oxidative insults. Exposure of cancer cells to subtoxic doses of Bet-CA leads to the significant enhancement of ROS in a temporal fashion. Furthermore, Bet-CA caused no significant generation of ROS in the fibroblastic cell line clarifying the ambiguity and ascertaining the paradigm for the selective killing property of Bet-CA. Of equal importance when cancer cells were challenged with a similar dose of BA, DCA or its stoichiometric mixture and analysed, there was no significant accumulation of intracellular ROS to immediate apoptosis and this phenomenology uncovered suggestively yet another simplifying notion and unequivocally concreted the synergistic potential of Bet-CA.
Cells cannot gain a growth of advantage by losing a mitochondrion and thereby damages inflicted upon it prove to be fatal. True to this fact, Bet-CA confers the degeneration of MMP, opening of MPTP and swelling of the mitochondria. Furthermore, the studies establish that Bet-CA treatment leads to the downregulation of Bcl-xl and activation Bax expression. They have critically determined that Cyt c efflux is followed by apoptosis via the caspase cascade in their experimentations. TUNEL assay documented DNA strand breakage and the phenomenon of apoptosis was further confirmed by dual colour mode flow cytometric analysis. These data are in general agreement with the observation that Bet-CA regulates the expression of apoptosis related proteins, leads to the release of Cyt c and initiates caspase mediated cell death. To detail the granularity for the selective potential of Bet-CA, its effect was studied on the normal cell line. Opposed to the effect Bet-CA poses on the neoplastic cells, there was no alteration in MMP, neither release of Cyt c nor increase in the levels of cleaved caspase-3. Additionally equivalent doses of BA, DCA or BA+DCA (1:1) failed to confer a degradation of ΔΨm or the release of Cyt c and observations readout a similar phenomenon straightway pointing the obvious hypothesis for the synergistic potential of Bet-CA. Therefore, what was a rather provocative hypothesis initially, gained a solid basis with ultimate precision factually obviating the selective and synergistic potential of Bet-CA to establish it as the futuristic version of medicine for tackling the nettlesome problems associated with therapy.
In vitro observations enticed them to explore and evaluate whether Bet-CA poses similar barriers to the growth of cancer cells in vivo. Their observations were further corroborated in syngeneic mice melanoma model and pulmonary metastatic melanoma model of BALB/c mice. Expectedly, Bet-CA treatment significantly limited tumor growth and metastatic nodule formation in lungs. The results clearly authenticate the apparent synergistic antitumor behaviour of this compound in vivo. Histological appearances of the organs in treated sets were normal depicting no level of toxicity of Bet-CA.
From the above studies they presented an important consequential agenda that Bet-CA is endowed with ability to target and kill cancer cells. Their data clearly indicate that Bet-CA might be considered a capable drug as it enforces repression of cancer cell proliferation in vitro and tumor initiation and growth in vivo without any toxic manifestations. The conjunction of a plant secondary metabolite with a small molecule presents a promising synergistic and encouraging selective strategy to circumvent malignancy and obliterate cytotoxicity. Based on our findings further elucidation of detailed course of action of Bet-CA is a riveting area and likely to resonate a substantial promise for the future.
Suchandrima Saha, Monisankar Ghosh and Samir Kumar Dutta, A potent tumoricidal co-drug ‘Bet-CA’ – an ester derivative of betulinic acid and dichloroacetate selectively and synergistically kills cancer cells, Scientific Reports 5, Article number: 7762 ｜doi:10.1038/srep07762.