Ding Ding Guo

Alpha‐eleostearic acid suppresses proliferation of MCF‐7 breast cancer cells via activation of PPARγ and inhibition of ERK 1 / 2

Alpha‐eleostearic acid (α‐ESA) is known to suppress the growth in cancer cells although its underlying molecular mechanisms have not been fully elucidated. The present study was designed to elucidate and evaluate the anticancer mechanism of α‐ESA on MCF‐7 breast cancer cells. Also, an attempt was made to better understand the anticancer mechanism by which α‐ESA activated PPARγ and attenuated the ERK1/2 MAPK phosphorylation state. The MCF‐7 breast cancer cell‐line and nontumorigenic MCF‐10A human mammary epithelial cells were treated with α‐ESA and compared with negative control (without treatment) and positive control groups (treated with rosiglitazone), and changes of apoptosis‐related molecules, PPARγ and pERK1/2 were examined. In MCF‐7 cells treated with α‐ESA, we found that the expression of p53, p21, and Bax was up‐regulated whereas expression of Bcl‐2 and procaspase‐9 was down‐regulated. Moreover, nuclear translocation of PPARγ by α‐ESA positively correlated with inhibition of ERK1/2 activation. Our data suggest that α‐ESA can be considered to be a PPARγ agonist and thus a candidate for a chemotherapeutic agent against breast cancer. (Cancer Sci 2009; 00: 000–000)

PEGylated conjugated linoleic acid stimulation of apoptosis via a p53-mediated signaling pathway in MCF-7 breast cancer cells

The objective of this study was to investigate whether PEGylated conjugated linoleic acid (PCLA), as compared with conjugated linoleic acid (CLA) alone, displays anti-cancer properties in MCF-7 breast cancer cells. To generate PCLA, CLA was simply coupled to poly(ethylene glycol) (PEG) at the melting state of PEG without a solvent or a catalyst. The coupling reaction generated an ester linkage between the carboxyl group of CLA and hydroxyl one of PEG. The half-life of the generated PCLA was 52h at pH 7.4 at 37 degrees C, indicating that PCLA potentially acts as a pro-drug. Apoptosis of MCF-7 breast cancer cells treated with PCLA showed a dose response to PCLA concentration during treatment. In addition, pro-apoptotic proteins such as Bax were up-regulated, whereas anti-apoptotic proteins, such as Bcl-2, were down-regulated by treatment with both CLA and PCLA. The tumor suppressor gene p53 was significantly up-regulated by treatment with increasing concentrations of PCLA, suggesting that PCLA-induced apoptosis is regulated by a p53-mediated signaling pathway. Overall, the anti-cancer effects of PCLA on MCF-7 breast cancer cells may have therapeutic significance.

Lipolysis is stimulated by PEGylated conjugated linoleic acid through the cyclic adenosine monophosphate-independent signaling pathway in 3T3-L1 cells: activation of MEK/ERK MAPK signaling pathway and hyper-secretion of adipo-cytokines.

We previously reported that PEGylated conjugated linoleic acid (PCLA) as a pro‐drug treatment of cultures of 3T3‐L1 cells containing differentiated adipocytes caused de‐differentiation by downregulation of PPARγ2‐induced adipogenesis, and cell apoptosis induced by PCLA was lower than that induced by conjugated linoleic acid (CLA) owing to the biocompatible and hydrophilic properties of poly(ethylene glycol) (PEG). To further investigate our previous observations, the present study is designed to evaluate the lipolytic action of PCLA and its role in biochemical signaling pathways of 3T3‐L1 cells when compared to the CLA itself. Although both CLA and PCLA stimulated lipolysis, our results indicated a sensitivity difference between CLA and PCLA treatment: a time‐dependent effect on lipolysis and p‐extracellular signal‐related kinases (ERK) expression was observed for PCLA‐treated, but not for CLA‐treated cultures. Also, the induction by PCLA of mitogen‐activated protein kinase kinase (MEK)/ERK mitogen‐activated protein kinase (MAPK) activation was linked to secretion of adipo‐cytokines, interleukin‐6 (IL‐6), and interleukin‐8 (IL‐8), in time‐dependent manners. Interestingly, adenylyl cyclase inhibitor, 2′, 5′‐dideoxyadenosine (DDA), pre‐treatment did not prevent PCLA‐stimulated lipolysis. In fact, isoproterenol, but not PCLA, caused a significant increase in cyclic adenosine monophosphate (cAMP) levels, suggesting that the PCLA‐induced lipolysis was not mediated in the conventional cAMP‐dependent pathway and the cAMP was the intracellular mediator for isoproterenol‐induced lipolysis. Overall, our findings provide support for a role for PCLA as a pro‐drug in the regulation of metabolism in adipose tissue. J. Cell. Physiol. 214: 283–294, 2008.

PEGylation of Conjugated Linoleic Acid and its Application as an Anti-Cancer Prodrug

The objective of this study is to investigate whether the PEGylated conjugated linoleic acid (PCLA) as an anti-cancer prodrug can have favorable stability, biological activity, and prevention of proliferation in MCF-7 breast cancer cells for anti-cancer when compared with conjugated linoleic acid (CLA) itself. The CLA was simply coupled to poly(ethylene glycol) (PEG) at melting state without solvent or catalyst through ester linkage between carboxylic group of CLA and hydroxyl one of PEG. The results showed that the half life of PCLA was 55h in cell culture medium at pH 7.4 and 37°C. Apoptosis of MCF-7 breast cancer cells were induced by not only CLA- but PCLA-treatment with increasing concentrations whereas PCLA increased cell viability when compared with CLA itself. These results indicate that the PCLA is a more stable and valuable prodrug in that it has good stability and inhibition of cancer cell proliferation.

Release of All-Trans Retinoic Acid (RA) from RA-Loaded Poly(Ester Amine) Based on Polyethylenimine and Polycaprolactone for Intracellular Delivery

The objective of this study is to develop a new type of cationic nanoparticles for the intracellular drug delivery to breast cancer. Poly(ester amine) (PEA) based on polyethylenimine and polycaprolactone was synthesized to make cationic PEA nanoparticles for all-trans retinoic acid (RA). In the 1H-NMR study, the proton signals of RA appeared in the spectrum of RA-loaded PEA nanoparticles in CDCL3, whereas they disappeared in D2O, suggesting that hydrophobic inner-core with hydrophilic outer-shell formed in water. RA release was faster at lower drug content and RA was released over a period of 20 days. RA-loaded PEA nanoparticles showed enhanced cytotoxicity compared with RA itself, whereas nanoparticles of PEA themselves did not show it. These results indicated that the cationic PEA provided an efficient intracellular delivery of RA.