N-(4-Hydroxyphenyl) retinamide induced both differentiation and apoptosis in human glioblastoma T98G and U87MG cells

Abstract

N-(4-Hydroxyphenyl) retinamide (4-HPR) is a synthetic retinoid that has shown biological activity against several malignant tumors and minimal side effects in humans. To explore the mechanisms underlying the chemotherapeutic effects of 4-HPR in glioblastoma, we used two human glioblastoma T98G and U87MG cell lines. In situ methylene blue staining showed the morphological features of astrocytic differentiation in glioblastoma cells following exposure to 1 µM and 2 µM 4-HPR for a short duration (24 h). Astrocytic differentiation was associated with an increase in expression of glial fibrillary acidic protein (GFAP) and down regulation of telomerase. Wright staining and ApopTag assay indicated appearance of apoptotic features in glioblastoma cells following exposure to 1 µM and 2 µM 4-HPR for a long duration (72 h). We found that 4-HPR caused apoptosis with activation of caspase-8 and cleavage of Bid to truncated Bid (tBid). Besides, apoptosis was associated with alterations in expression of pro-apoptotic Bax and anti-apoptotic Bcl-2 proteins resulting in an increase in Bax:Bcl-2 ratio, mitochondrial release of cytochrome c and Smac, down regulation of selective baculoviral inhibitor-of-apoptosis repeat containing (BIRC) molecules, an increase in intracellular free [Ca 2+ ], and activation of calpain and caspase-3. Taken together, these results strongly suggested that 4-HPR could be used at low doses for induction of both differentiation and apoptosis in human glioblastoma cells.

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“…We analyzed the levels of specific proteins in the cells using the Western blotting, as we described previously (Karmakar et al, 2007; Das et al, 2008). Briefly, VSC 4.1 cells were grown in T-75 flasks, treated as described above, and harvested following treatment.…”

Drug Resistance in Glioblastoma: A Mini Review

“…Most research indicates that retinoids, while successful at inducing differentiation, fail to induce apoptosis. We determined that N-(4-hydroxyphenyl) retinamide (4-HPR), also called fenretinide, a synthetic analog of all- trans retinoic acid (ATRA), can exhibit both anti-proliferative and pro-apoptotic effects [55]. 4-HPR has the potential for greater efficacy than its natural counterpart, ATRA, both because it has fewer side effects and because it has proven to be active even in ATRA-resistant cells [56].…”

“…This difference is due to the fact that 4-HPR causes apoptosis via retinoid receptor-independent mechanisms, unlike the naturally occurring compound [57]. In a study, we examined the effects of various concentrations of 4-HPR on two different GBM cell lines and determined that treatment with 4-HPR caused both differentiation and apoptosis in both GBM cell lines [55]. Differentiation occurred earlier during exposure, while apoptosis was a final stage event (72 hours) [55].…”

Salinomycin induces endoplasmic reticulum stress-mediated autophagy and apoptosis through generation of reactive oxygen species in human glioma U87MG cells

“…Despite multidisciplinary treatments including surgery, chemotherapy and radiotherapy, it has a poor prognosis with a median survival of less than 15 months (9). Moreover, although chemotherapy has been used most extensively in glioma cancer patients and has contributed to substantial improvement in the survival rate, it was ultimately confirmed to be ineffective owing to severe toxicity, the incapacity of many drugs to cross the blood-brain barrier and high levels of drug resistance (10).…”