Cancer:
Nasopharyngeal., ER α degradation, Lung, breast, oral., glioblastoma, liver cancer prevention
Action: Cytostatic, radio-sensitizing, chemo-sensitizing
Nasopharyngeal Carcinoma
Aloe-emodin (AE), a natural., biologically active compound from Aloe vera leaves has been shown to induce apoptosis in several cancer cell lines in vitro. Investigation showed that AE induced G2/M phase arrest by increasing levels of cyclin B1 bound to Cdc2, and also caused an increase in apoptosis of nasopharyngeal carcinoma (NPC) cells, which was characterized by morphological changes, nuclear condensation, DNA fragmentation, caspase-3 activation, cleavage of poly (ADP-ribose) polymerase (PARP) and increased sub-G(1) population. Treatment of NPC cells with AE also resulted in a decrease in Bcl-X(L) and an increase in Bax expression.
Collectively, results indicate that the caspase-8-mediated activation of the mitochondrial death pathway plays a critical role in AE-induced apoptosis of NPC cells (Lin et al., 2010).
Glioblastoma
Aloe emodin arrested the cell-cycle in the S phase and promoted the loss of mitochondrial membrane potential in glioblastoma U87 cells that indicated the early event of the mitochondria-induced apoptotic pathway. It plays an important role in the regulation of cell growth and death (Ismail et al., 2013).
Breast Cancer
The anthraquinones emodin and aloe-emodin are also abundant in the rhizome Rheum palmatum and can induce cytosolic estrogen receptor α (ER α) degradation; it primarily affected nuclear ER α distribution similar to the action of estrogen when protein degradation was blocked. In conclusion, our data demonstrate that emodin and aloe-emodin specifically suppress breast cancer cell proliferation by targeting ER α protein stability through distinct mechanisms (Huang et al., 2013).
Lung Cancer
Photoactivated aloe-emodin induced anoikis and changes in cell morphology, which were in part mediated through its effect on cytoskeleton in lung carcinoma H460 cells. The expression of protein kinase Cδ (PKCδ) was triggered by aloe-emodin and irradiation in H460 cells. Furthermore, the photoactivated aloe-emodin-induced cell death and translocation of PKCδ from the cytosol to the nucleus was found to be significantly inhibited by rottlerin, a PKCδ-selective inhibitor (Chang et al., 2012).
Oral Cancer; Radio-sensitizing, Chemo-sensitizing
The treatment of cancer with chemotherapeutic agents and radiation has two major problems: time-dependent development of tumor resistance to therapy (chemoresistance and radioresistance) and nonspecific toxicity toward normal cells. Many plant-derived polyphenols have been studied intensively for their potential chemo-preventive properties and are pharmacologically safe.
These compounds include genistein, curcumin, resveratrol, silymarin, caffeic acid phenethyl ester, flavopiridol, emodin, green tea polyphenols, piperine, oleandrin, ursolic acid, and betulinic acid. Recent research has suggested that these plant polyphenols might be used to sensitize tumor cells to chemotherapeutic agents and radiation therapy by inhibiting pathways that lead to treatment resistance. These agents have also been found to be protective from therapy-associated toxicities.
Treatment with aloe-emodin at 10 to 40 microM resulted in cell-cycle arrest at G2/M phase. The alkaline phosphatase (ALP) activity in KB cells increased upon treatment with aloe-emodin when compared to controls. This is one of the first studies to focus on the expression of ALP in human oral carcinomas cells treated with aloe-emodin. These results indicate that aloe-emodin has anti-cancer effect on oral cancer, which may lead to its use in chemotherapy and chemo-prevention of oral cancer (Xiao et al., 2007).
Liver Cancer Prevention
In Hep G2 cells, aloe-emodin-induced p53 expression and was accompanied by induction of p21 expression that was associated with a cell-cycle arrest in G1 phase. In addition, aloe-emodin had a marked increase in Fas/APO1 receptor and Bax expression. In contrast, with p53-deficient Hep 3B cells, the inhibition of cell proliferation of aloe-emodin was mediated through a p21-dependent manner that did not cause cell-cycle arrest or increase the level of Fas/APO1 receptor, but rather promoted aloe-emodin-induced apoptosis by enhancing expression of Bax.
These findings suggest that aloe-emodin may be useful in liver cancer prevention (Lian et al., 2005).
References