Molto importante, in alternativa alla Low Dose Rapamycin
http://www.fasebj.org/cgi/content/meeting_abstract/24/1_MeetingAbstracts/lb259
The effect of anthocyanins on cancer cell survival and AMPK/mTOR pathway was compared with a classical mTOR inhibitor rapamycin, and anthocyanins were found to inhibit growth through mTOR comparable to rapamycin. Moreover, anthocyanins stimulated â-catenin degradation through GSK3â activation, and it seemed to be regulated by AMPK. This work has shown that the cell energy controller AMPK can control two important cell growth regulators mTOR and Wnt, and the modulation of AMPK/mTOR or AMPK/Wnt pathways by phytochemicals such as anthocyanins can further strengthen the use of phytochemicals for cancer control.
http://mct.aacrjournals.org/content/7/8/2476.full sugli inaspettati legami tra stratefia longevista e cura del cancro.
Sembra che i meccanismi che portano a una lunga vita siano simili ai meccanismi impiegati dai tumori per prolongare la loro vita all'interno dell'organismo. vedi anche http://dx.doi.org/10.1016/j.bbamcr.2009.01.006
Discussion
The results obtained in this study show that the anthocyanins obtained from P. lentiscus berries have the strongest DPPH radical and H2O2 scavenging activities. Moreover, their scavenging effects are comparable to those of á-tocopherol, one of the strongest natural antioxidants, and Trolox, its water-soluble analogue. The higher scavenging activity of P. lentiscus anthocyanins is probably due to the presence of the monoglucoside of delphinidin, which possesses the highest radical scavenging activity among the anthocyanins present in the berries of this plant (14).
The present study provides evidence to show the induction of both autophagic and apoptotic machineries in HCC cells upon treatment with anthocyanins, which are highly promising cancer chemopreventive constituents of several vegetables (29, 30). This was not unexpected because many natural products are known to possess antioxidant and anticancer properties. Anthocyanins inhibit oxidative stress–induced apoptosis by elevating the cellular antioxidant capacity (31–33). On the other hand, they contribute to the antiproliferative activity of vegetables and fruits, including berries, by inducing the apoptosis of cancer cells (29, 30, 34–37). Despite their antioxidant action, paradoxically, they exhibit pro-oxidant activity resulting in selective cell death of leukemia cells (37).
The highest cytotoxicity against HCC cells is shown by P. lentiscus anthocyanins, which also displayed the strongest antioxidant activity. The in vitro anticancer activity is due to the combined induction of the apoptotic program, G1 arrest, and reduced DNA synthesis. The apoptotic response has been observed in response to various anticancer stimuli, including natural products (38); however, failure in HCC cure results from the development of drug resistance, the rates of HCC incidence and mortality being similar (16).
Here, we report for the first time a novel function of antocyanins; the induction of autophagy, as shown by activation of the autophagosomal marker LC3 and incorporation of monodansylcadaverine in autolysosomes. This was possibly triggered by down-regulation of Bcl-2 and mTOR associated with up-regulation of eIF2á signaling pathways. Autophagy displays a dual conflicting function in cancer cell biology. We have shown that HCC down-regulates autophagic activity (39, 40), and recently, autophagy has been proposed as a tumor suppression mechanism, underlying the possibility that activation of autophagy reverses the neoplastic phenotype (25, 41). On the contrary, in the present article, inhibition of autophagy enhanced apoptosis, indicating that autophagy contributes to tumor progression as a protective mechanism against stressful conditions (25, 42, 43). Autophagy optimizes nutrient utilization in rapidly growing cells when faced with hypoxic or metabolic stress, similar to therapeutic assault, and removes organelles that are sources or targets of lethal levels of free radical–induced damage (44). Thus, lack of autophagy for a long period of time results in the accumulation of intracellular oxidants that enhance the probability of transformation. Yet, the same mechanism protects the cells of established cancers against various stressors.
The autophagic pathway is a novel therapeutic target for cancer treatment (20, 25, 42, 45). Anticancer treatments, including drugs, activate autophagy to kill cancer cells resistant to apoptosis. Yet, in HCC cells, a deficiency of autophagy enhances anthocyanin-induced cell demise. Paglin et al. (46) shows for the first time the possibility of treating cancer cells by autophagy inhibition because cancer cells respond to radiation by inducing autophagy. Autophagy inhibition enhances the anticancer effect of arsenic trioxide (20), hyperthermia (20), sulforaphane (47), and p53 or alkylating drugs (48). These and our observations indicate that autophagy protects cancer cells from therapy-induced apoptosis and that autophagy inhibitors strengthen the efficacy of proapoptotic chemotherapeutic strategies. Again, autophagy is commonly induced by hypoxia and it represents the ultimate nutritional source for tumor cells to survive low-nutrient conditions (20), thus suppression of autophagy in combination with other treatments accelerates tumor necrosis (27, 43).
In HCC cells, we eliminate the expression of Atg5 protein to inhibit autophagy because Atg5 is required for the formation of the autophagosome (23–25) and it is a novel proapoptotic factor (49). However, we rule out the possibility that Atg5 is involved in anthocyanin-induced apoptosis. Autophagy is regulated by class III phosphoinositide-3-kinase complex which is the putative target of 3-MA. Inhibition of anthocyanin-induced autophagy in the presence of 3-MA indicates the involvement of a class III phosphoinositide-3-kinase complex. This complex includes Beclin 1, a protein first identified as a novel Bcl-2–interacting protein, the binding of Bcl-2 to Beclin 1 disrupting its autophagic function (25, 28). Here, we have shown that anthocyanin treatment causes a decrease in the level of Bcl-2 protein in HCC cells. This suggests that anthocyanin disrupts the interaction between Bcl-2 and Beclin 1 in the trans-Golgi network to induce autophagy followed by the binding of Bcl-2 to Bax in the mitochondria to switch autophagy to apoptosis. Alternatively, because mTOR inhibition increases the levels of activated LC3 (25, 27), anthocyanins might directly target mTOR to induce autophagy.
In conclusion, our observations indicate that autophagy inhibition helps to enhance the chemopreventive/therapeutic activity of anthocyanin towards HCC. Future experiments are required to extend these preclinical in vitro results to evaluate the effect of anthocyanin treatment in mouse tumor models in support of potential clinical studies. In animal models, anthocyanins act as anticancer agents by protecting against genomic instability at various phases of the carcinogenic process, yet, the effect in human studies is weak (50). This study suggests that the anthocyanins obtained from P. latifolia, R. peregrina, and P. lentiscus berries could be used as an easily accessible and abundant source of natural antioxidants as potential food additives and pharmaceutical agents.