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Omega-3 Polyunsaturated Fatty Acids Trigger Cell Cycle Arrest and Induce Apoptosis in Human Neuroblastoma LA-N-1 Cells.

So WW, Liu WN, Leung KN - Nutrients (2015)

Bottom Line: Omega-3 (n-3) fatty acids are dietary long-chain fatty acids with an array of health benefits.Up-regulation of Bax, activated caspase-3 and caspase-9 proteins, and down-regulation of Bcl-XL protein, might account for the occurrence of apoptotic events.Collectively, our results suggest that the growth-inhibitory effect of DHA and EPA on LA-N-1 cells might be mediated, at least in part, via triggering of cell cycle arrest and apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Biochemistry Programme, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China. timothyso30@hotmail.com.

ABSTRACT
Omega-3 (n-3) fatty acids are dietary long-chain fatty acids with an array of health benefits. Previous research has demonstrated the growth-inhibitory effect of n-3 fatty acids on different cancer cell lines in vitro, yet their anti-tumor effects and underlying action mechanisms on human neuroblastoma LA-N-1 cells have not yet been reported. In this study, we showed that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) exhibited time- and concentration-dependent anti-proliferative effect on the human neuroblastoma LA-N-1 cells, but had minimal cytotoxicity on the normal or non-tumorigenic cells, as measured by MTT reduction assay. Mechanistic studies indicated that DHA and EPA triggered G0/G1 cell cycle arrest in LA-N-1 cells, as detected by flow cytometry, which was accompanied by a decrease in the expression of CDK2 and cyclin E proteins. Moreover, DHA and EPA could also induce apoptosis in LA-N-1 cells as revealed by an increase in DNA fragmentation, phosphatidylserine externalization and mitochondrial membrane depolarization. Up-regulation of Bax, activated caspase-3 and caspase-9 proteins, and down-regulation of Bcl-XL protein, might account for the occurrence of apoptotic events. Collectively, our results suggest that the growth-inhibitory effect of DHA and EPA on LA-N-1 cells might be mediated, at least in part, via triggering of cell cycle arrest and apoptosis. Therefore, DHA and EPA are potential anti-cancer agents which might be used for the adjuvant therapy or combination therapy with the conventional anti-cancer drugs for the treatment of some forms of human neuroblastoma with minimal toxicity.

No MeSH data available.


Related in: MedlinePlus

Effects of DHA and EPA on the expression levels of activated caspases in LA-N-1 cells. (A) LA-N-1 cells were incubated with various concentrations of EPA (Lanes 2, 3 and 4) or DHA (Lanes 5, 6 and 7) for 48 hours. Cells treated with ethanol (Lane 1) acted as the control. The protein expression levels of activated caspase-3, caspase-8 and caspase-9 were measured by Western blotting with β-actin serving as an internal control. The relative protein expression levels of activated caspase-3, caspase-8 and caspase-9 in DHA-treated cells (B–D) and EPA-treated cells (E–G) as compared to β-actin were quantified. The results are expressed as relative protein expression levels ± SD. ** p < 0.01, *** p < 0.001.
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nutrients-07-05319-f007: Effects of DHA and EPA on the expression levels of activated caspases in LA-N-1 cells. (A) LA-N-1 cells were incubated with various concentrations of EPA (Lanes 2, 3 and 4) or DHA (Lanes 5, 6 and 7) for 48 hours. Cells treated with ethanol (Lane 1) acted as the control. The protein expression levels of activated caspase-3, caspase-8 and caspase-9 were measured by Western blotting with β-actin serving as an internal control. The relative protein expression levels of activated caspase-3, caspase-8 and caspase-9 in DHA-treated cells (B–D) and EPA-treated cells (E–G) as compared to β-actin were quantified. The results are expressed as relative protein expression levels ± SD. ** p < 0.01, *** p < 0.001.

Mentions: Apoptosis can be triggered by both intrinsic and extrinsic pathways, and the mitochondrial dysfunction is the major characteristic of the intrinsic pathway [30]. To unravel the molecular mechanisms of the occurrence of apoptosis, the protein expression levels of several apoptosis-regulatory proteins and different caspase proteins were examined by Western blot analysis. It could be seen that the expression level of the pro-apoptotic Bax protein was increased, accompanied by a decrease in the expression level of the anti-apoptotic Bcl-XL protein in a concentration-dependent manner in both the DHA-treated (Figure 6A–C) or EPA-treated cells (Figure 6A,D,E). It was reported that Bax and Bcl-XL in the Bcl-2 family are responsible to elicit the intrinsic pathway of apoptosis [31]. Furthermore, our results suggested that the protein expression levels of activated caspase-3 (Figure 7A,B,E) and caspase-9 (Figure 7A,D,G) increased after treatment of DHA or EPA, whereas the expression level of activated caspase-8 protein did not alter significantly (Figure 7A,C,F). Collectively, our results suggest that the occurrence of apoptosis triggered by DHA and EPA on LA-N-1 cells might be mediated via the intrinsic pathway but not the extrinsic pathway.


Omega-3 Polyunsaturated Fatty Acids Trigger Cell Cycle Arrest and Induce Apoptosis in Human Neuroblastoma LA-N-1 Cells.

So WW, Liu WN, Leung KN - Nutrients (2015)

Effects of DHA and EPA on the expression levels of activated caspases in LA-N-1 cells. (A) LA-N-1 cells were incubated with various concentrations of EPA (Lanes 2, 3 and 4) or DHA (Lanes 5, 6 and 7) for 48 hours. Cells treated with ethanol (Lane 1) acted as the control. The protein expression levels of activated caspase-3, caspase-8 and caspase-9 were measured by Western blotting with β-actin serving as an internal control. The relative protein expression levels of activated caspase-3, caspase-8 and caspase-9 in DHA-treated cells (B–D) and EPA-treated cells (E–G) as compared to β-actin were quantified. The results are expressed as relative protein expression levels ± SD. ** p < 0.01, *** p < 0.001.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4555158&req=5

nutrients-07-05319-f007: Effects of DHA and EPA on the expression levels of activated caspases in LA-N-1 cells. (A) LA-N-1 cells were incubated with various concentrations of EPA (Lanes 2, 3 and 4) or DHA (Lanes 5, 6 and 7) for 48 hours. Cells treated with ethanol (Lane 1) acted as the control. The protein expression levels of activated caspase-3, caspase-8 and caspase-9 were measured by Western blotting with β-actin serving as an internal control. The relative protein expression levels of activated caspase-3, caspase-8 and caspase-9 in DHA-treated cells (B–D) and EPA-treated cells (E–G) as compared to β-actin were quantified. The results are expressed as relative protein expression levels ± SD. ** p < 0.01, *** p < 0.001.
Mentions: Apoptosis can be triggered by both intrinsic and extrinsic pathways, and the mitochondrial dysfunction is the major characteristic of the intrinsic pathway [30]. To unravel the molecular mechanisms of the occurrence of apoptosis, the protein expression levels of several apoptosis-regulatory proteins and different caspase proteins were examined by Western blot analysis. It could be seen that the expression level of the pro-apoptotic Bax protein was increased, accompanied by a decrease in the expression level of the anti-apoptotic Bcl-XL protein in a concentration-dependent manner in both the DHA-treated (Figure 6A–C) or EPA-treated cells (Figure 6A,D,E). It was reported that Bax and Bcl-XL in the Bcl-2 family are responsible to elicit the intrinsic pathway of apoptosis [31]. Furthermore, our results suggested that the protein expression levels of activated caspase-3 (Figure 7A,B,E) and caspase-9 (Figure 7A,D,G) increased after treatment of DHA or EPA, whereas the expression level of activated caspase-8 protein did not alter significantly (Figure 7A,C,F). Collectively, our results suggest that the occurrence of apoptosis triggered by DHA and EPA on LA-N-1 cells might be mediated via the intrinsic pathway but not the extrinsic pathway.

Bottom Line: Omega-3 (n-3) fatty acids are dietary long-chain fatty acids with an array of health benefits.Up-regulation of Bax, activated caspase-3 and caspase-9 proteins, and down-regulation of Bcl-XL protein, might account for the occurrence of apoptotic events.Collectively, our results suggest that the growth-inhibitory effect of DHA and EPA on LA-N-1 cells might be mediated, at least in part, via triggering of cell cycle arrest and apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Biochemistry Programme, School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, China. timothyso30@hotmail.com.

ABSTRACT
Omega-3 (n-3) fatty acids are dietary long-chain fatty acids with an array of health benefits. Previous research has demonstrated the growth-inhibitory effect of n-3 fatty acids on different cancer cell lines in vitro, yet their anti-tumor effects and underlying action mechanisms on human neuroblastoma LA-N-1 cells have not yet been reported. In this study, we showed that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) exhibited time- and concentration-dependent anti-proliferative effect on the human neuroblastoma LA-N-1 cells, but had minimal cytotoxicity on the normal or non-tumorigenic cells, as measured by MTT reduction assay. Mechanistic studies indicated that DHA and EPA triggered G0/G1 cell cycle arrest in LA-N-1 cells, as detected by flow cytometry, which was accompanied by a decrease in the expression of CDK2 and cyclin E proteins. Moreover, DHA and EPA could also induce apoptosis in LA-N-1 cells as revealed by an increase in DNA fragmentation, phosphatidylserine externalization and mitochondrial membrane depolarization. Up-regulation of Bax, activated caspase-3 and caspase-9 proteins, and down-regulation of Bcl-XL protein, might account for the occurrence of apoptotic events. Collectively, our results suggest that the growth-inhibitory effect of DHA and EPA on LA-N-1 cells might be mediated, at least in part, via triggering of cell cycle arrest and apoptosis. Therefore, DHA and EPA are potential anti-cancer agents which might be used for the adjuvant therapy or combination therapy with the conventional anti-cancer drugs for the treatment of some forms of human neuroblastoma with minimal toxicity.

No MeSH data available.


Related in: MedlinePlus