CannaScience / L’importanza dei cannabinoidi nella cura e nella prevenzione dei tumori
Possible Endocannabinoid Control of Colorectal Cancer Growth, Gastroenterology, 2003, ALESSIA LIGRESTI, TIZIANA BISOGNO,ISABEL MATIAS,* LUCIANO DE PETROCELLIS, MARIA GRAZIA CASCIO, VITTORIO COSENZA, GIUSEPPE D’ARGENIO, GIUSEPPE SCAGLIONE, MAURIZIO BIFULCO,ITALO SORRENTINI, and VINCENZO DI MARZO
Lo studio del 2003 riporta che numerosi dati sperimentali indicano che l’attivazione dei cannabinoidi endogeni rappresentano una strategia efficace per la creazione di medicinali antitumorali. Lo studio del 2003 dimostra che gli endocannabinoidi sono sovraprodotti nei tumori, in particolare nel tumore al colon e negli adenomi. Questo permette di esercitare sia un’azione di inibizione dei tumori sia da marker per misurare il livello di invasività e malignità.
“The endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) inhibit cancer cell proliferation by acting at cannabinoid receptors (CBRs). We studied (1) the levels of endocannabinoids, cannabinoid CB1 and CB2 receptors, and fatty acid amide hydrolase
(FAAH, which catalyzes endocannabinoid hydrolysis) in colorectal carcinomas (CRC), adenomatous polyps, and neighboring healthy mucosa; and (2) the effects of endocannabinoids, and of inhibitors of their inactivation, on human CRC cell proliferation.
Methods: Tissues were obtained from 21 patients by biopsy during colonoscopy.
Endocannabinoids were measured by liquid chromatography-mass spectrometry (LC-MS) .CB1,CB2, and FAAH expression were analyzed by RT-PCR and Western immunoblotting .CRC cell lines (CaCo-2 and DLD-1) were used to test antiproliferative effects.
All tissues and cells analyzed contain anandamide, 2-AG, CBRs, and FAAH .The
levels of the endocannabinoids are 3- and 2-fold higher in adenomas and CRCs than normal mucosa .Anandamide, 2-AG, and the CBR agonist HU-210 potently inhibit CaCo-2 cell proliferation .This effect is blocked by the CB1 antagonist SR141716A, but not by the CB2 antagonist SR144528, and is mimicked by CB1 -selective, but not CB2 selective, agonists .In DLD-1 cells, both CB1 and CB2 receptors mediate inhibition of proliferation .Inhibitors of endocannabinoid inactivation enhance CaCo-2 cell endocannabinoid levels and block cell proliferation, this effect being antagonized by SR141716A .CaCo-2 cell differentiation into noninvasive cells results in increased FAAH expression, lower endocannabinoid levels, and no responsiveness to cannabinoids.
Conclusions: Endocannabinoid levels are enhanced in transformed colon mucosa cells
possibly to counteract proliferation via CBRs .Inhibitors of endocannabinoid inactivation may prove useful anticancer agents.
Numerous experimental data indicate that the activation of the endogenous cannabinoid system might represent a potential strategy for the development of new anticancer drugs. First, the psychoactive principle of Cannabis sativa and marijuana, Δ9-tetrahydrocannabinol,3 is known to act mostly by stimulating 2 specific receptors subtypes, the cannabinoid CB1 and CB2 receptors4, and was reported in the past5 and more recently6 to have antineoplastic activity in vivo and in vitro.1, 2 Second, endogenous agonists of the cannabinoid receptors (CBRs), i.e., N-arachidonoyl-ethanolamine (AEA; anandamide),7 2-arachidonoyl-glycerol (2-AG),8, 9 and noladin ether,10 or their metabolically stable synthetic analogs, were found to inhibit, mostly via CB1 receptors, the proliferation of breast and prostate cancer cells in vitro11, 12 and of rat thyroid cells transformed by the product of the K-ras oncogene in vivo.13 Finally, stimulation of the 2 CBR subtypes has been found to influence the expression of various genes involved in cell survival, proliferation, and apoptosis via interference with cAMP- and ceramide-mediated signalling, mitogen-activated protein kinases and phosphatidyl-inositol-3-kinase (see Guzman et al.14 for review).Apart from the proposed role of CBRs in the control of cancer cell growth, transformation, and death,2, 14 there are at least 3 reasons why the endocannabinoids might be involved in the control of colorectal cancer cell proliferation. First, both AEA and 2-AG are good substrates for cyclooxygenase 2 (COX-2), which seems to play a major role in the development of colorectal carcinoma (CRC).
We found that human colon mucosa tissues contain both AEA and 2-AG and express CB1 and CB2 receptors as well as FAAH. The endocannabinoids and FAAH previously have been described to occur in mouse and rat whole colon, but we found here that the levels of both AEA and 2-AG increase dramatically when passing from normal mucosa to adenomatous polyps and then slightly decrease in CRC tissue. These changes are likely to result in corresponding changes in endocannabinoid tissue concentrations. we undertook a series of experiments aimed at investigating whether (1) endocannabinoids do inhibit colon cancer cell growth in vitro; (2) substances that inhibit endocannabinoid inactivation, and hence enhance the amounts of endocannabinoids produced by CRC cells in culture, also inhibit the proliferation of these cells; and (3) changes in endocannabinoid signaling occur in CRC cells also during their differentiation in culture. We used a widely employed cell line for the study of CRC, the CaCo-2 cells, which have the special feature of being capable of differentiating in culture after having reached confluence, thus becoming more similar to enterocytes.27 We found that AEA, 2-AG, and the ultra-potent CBR agonist HU-210 inhibited CaCo-2 cell proliferation with IC50 values in the submicromolar range and with relative potencies (HU-210>>AEA≥2-AG) that reflect their relative potencies at cannabinoid CB1 receptors.hree further observations strongly supported the involvement of this receptor subtype in endocannabinoid antiproliferative effects. First, 2 agonists selective for CB1 vs. CB2 receptors, i.e., arachidonoyl-chloro-anandamide (ACEA) and N-arachidonoyl-dopamine (NADA), the latter of which is much more stable to enzymatic hydrolysis than AEA, but less potent on CB1 receptors than AEA,28 inhibited CaCo-2 cell proliferation with the rank of potency expected from their relative affinity for CB1 receptors (ACEA>NADA), whereas the CB2-selective agonist BML-190 was inactive. Second, the effect of AEA, HU-210, and NADA (which is also an agonist for the VR1 receptor for capsaicin28) was entirely antagonized by the selective CB1 receptor antagonist SR141716A but not by the selective CB2 receptor antagonist SR144528. Finally, we found that CaCo-2 cells express the CB1 receptor, whereas no evidence for the presence of CB2 was found. We also assessed the effect of the endocannabinoids and of HU-210 and BML-190 in another CRC cell line, the nondifferentiating DLD-1 cells. In this case, stimulation of both CB1 and CB2 receptors led to inhibition of cell growth, in agreement with the presence of both receptor subtypes in these cells. However, CB1 receptors appeared to be less expressed in DLD-1 cells than in CaCo-2 cells, and this finding, together with the observation that DLD-1 cells were clearly less responsive to cannabimimetics than CaCo-2 cells, might suggest that CB1 receptors are more important than CB2 receptors in causing blockade of CRC cell proliferation. In summary, we found that, depending on the CRC cell line, either selective CB1 receptor stimulation (as previously found for breast and prostate cancer cells11, 12) or activation of both CB1 and CB2 receptors causes inhibition of proliferation. These findings are in agreement with the presence of both CBR subtypes in colon normal mucosa and CRC (Figure 1B) and suggest that endocannabinoids, present in high amounts in CRCs and, particularly, colorectal adenomas, might function as endogenous inhibitors of cancer growth.
In conclusion, we have shown that endocannabinoids (1) are overproduced in cancerous and, particularly, precancerous (i.e., adenomas) colon tissue and (2) exert a growth-inhibitory effect on CRC cells in culture, in which the extent of their action and levels seems to depend on the degree of differentiation (and malignancy/invasiveness) of these cells. The antiproliferative effects of the endocannabinoids are exerted in a large part by stimulation of CBRs, which are expressed in both colorectal mucosa and CRC cells. However, these compounds might act also by inhibiting COX-2, a possibility that, although not supported by our present data, deserves further investigation. Whatever their mechanism of action, endocannabinoids can be regarded as potential endogenous tumor growth inhibitors as well as possible markers for cancer cells. This hypothesis is strengthened by a recent preliminary study showing that AEA levels are increased in other tumors, including those whose growth was previously shown to be inhibited by endocannabinoids. Metabolically stable substances that act by stimulating CBRs directly might exert anticancer actions in this as well as other type of tumors. However, in view of the possible multiple mechanisms of action of endocannabinoids, the potential undesired psychotropic effect of CB1 receptor agonists, and the tonic inhibition on cancer growth suggested here for endocannabinoids, substances that act selectively by enhancing further the tumor levels of AEA and 2-AG, such as inhibitors of their cellular uptake and enzymatic hydrolysis, might provide for a more efficacious and tolerable therapeutic strategy against not only CRC but also other types of cancer. In support of this possibility, we have found in a separate study (V. Di Marzo, G. Portella and M. Bifulco, manuscript in preparation) that the growth of transformed thyroid cells in athymic mice is inhibited efficaciously by the AMT inhibitor VDM and by the FAAH inhibitor arachidonyl-serotonin via enhancement of tumoral endocannabinoid levels”.
Testo estratto da Possible Endocannabinoid Control of Colorectal Cancer Growth,Gastroenterology, 2003, ALESSIA LIGRESTI, TIZIANA BISOGNO,ISABEL MATIAS,* LUCIANO DE PETROCELLIS, MARIA GRAZIA CASCIO, VITTORIO COSENZA, GIUSEPPE D’ARGENIO, GIUSEPPE SCAGLIONE, MAURIZIO BIFULCO,ITALO SORRENTINI, and VINCENZO DI MARZO