Mitochondrial targeted peptides for cancer therapy

Anticancer potential of bioactive peptides from animal sources (Review)

Cancer is the most common cause of human death worldwide. Conventional anticancer therapies, including chemotherapy and radiation, are associated with severe side effects and toxicities as well as low specificity. Peptides are rapidly being developed as potential anticancer agents that specifically target cancer cells and are less toxic to normal tissues, thus making them a better alternative for the prevention and management of cancer. Recent research has focused on anticancer peptides from natural animal sources, such as terrestrial mammals, marine animals, amphibians, and animal venoms. However, the mode of action by which bioactive peptides inhibit the proliferation of cancer cells remains unclear. In this review, we present the animal sources from which bioactive peptides with anticancer activity are derived and discuss multiple proposed mechanisms by which these peptides exert cytotoxic effects against cancer cells.

Eugenol alleviated breast precancerous lesions through HER2/PI3K-AKT pathway-induced cell apoptosis and S-phase arrest

Eugenol can be separated from the oil extract of clove bud, and has many pharmacological functions such as anticancer and transdermal absorption. HER2/PI3K-AKT is a key signaling pathway in the development of breast cancer. In this study, 80 μM eugenol could significantly inhibit the proliferation of HER-2 positive MCF-10AT cells and the inhibition rate was up to 32.8%, but had no obvious inhibitory effect on MCF-7 and MCF-10A cells with HER2 weak expression. Eugenol also significantly induced human breast precancerous lesion MCF-10AT cell apoptosis and cell cycle S-phase arrest, but the biological effects nearly disappeared after HER2 over-expression through transfecting pcDNA3.1-HER2. In MCF-10AT cells treated by 180 μM eugenol, the protein expressions of HER2, AKT, PDK1, p85, Bcl2, NF-κB, Bad and Cyclin D1 were decreased and the decreased rates were respectively 63.0%, 60.0%, 52.9%, 62.9%, 37.1%, 47.2%, 61.7%, 59.1%, while the p21, p27 and Bax expression were increased by 4.48-, 4.76- and 2.57-fold respectively. In the rat models of breast precancerous lesion, 1 mg eugenol for external use significantly inhibited the progress of breast precancerous lesion and the occurrence rate of breast precancerous lesions and invasive carcinomas was decreased by about 30.5%. Furthermore eugenol for external (1 mg) markedly decreased the protein expressions of HER2 (62.9%), AKT (58.6%), PDK1 (56.4%), p85 (54.3%), Bcl2 (59.3%), NF-κB (65.7%), Bad (64.0%), Cyclin D1 (43.0%), while p21, p27 and Bax protein expressions were respectively increased 1.83-, 2.52- and 2.51-fold. The results showed eugenol could significantly inhibit the development of breast precancerous lesions by blocking HER2/PI3K-AKT signaling network. So eugenol may be a promising external drug for breast precancerous lesions.

Sinularin induces DNA damage, G2/M phase arrest, and apoptosis in human hepatocellular carcinoma cells

Background

Sinularin isolated from the cultured soft coral Sinularia flexibilis has been reported to exert potent cytotoxic effects against particular types of cancer. This study was carried out to investigate the cytotoxic effects in sinularin-treated human hepatocellular carcinoma cells, HepG2, and to subsequently explore the underlying molecular mechanisms.

Methods

TheMTT (3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyl- tetrazolium bromide) method was used to evaluate the cytotoxicity of sinularin on HepG2 and Hep3B cell lines. Furthermore, the cell cycle distribution assay, apoptosis assay, and western blot analysis in vitro were used to explore the possible mechanisms of action.

Results

From the results of our study, cell viability was obviously inhibited by sinularin in a dose-dependent manner. In addition, our results suggested that sinularin triggered DNA damage and subsequently induced cell cycle G2/M arrest associated with up-regulation of p-ATM (Ser(1981)), p-Chk2 (Tyr(68)), p-cdc2 (Tyr(15)), and p53 coupled with increased expression of downstream proteins p21 and down-regulation of p-cdc25 (Ser(216)). Moreover, the results of the apoptosis assay and western blot analysis indicated that the cytotoxic activity could be related to mitochondrial apoptosis, characterized by decrease of Bcl-2 expression, disruption of mitochondrial membrane potential, and sequential activation of caspases and Poly (ADP-ribose) polymerase (PARP).

Conclusions

This study reveals for the first time the anti-HCC activities of sinularin, the active compound isolated from the cultured soft coral Sinularia flexibilis. We believe that our results warrant further evaluation of sinularin as a new anti-HCC chemotherapeutic agent.

MicroRNA-206, let-7a and microRNA-21 pathways involved in the anti-angiogenesis effects of the interval exercise training and hormone therapy in breast cancer

AIMS

MicroRNAs (miRNAs) are the targeting signal-transduction pathways that can mediate tumorigenesis via their down and/or up-regulation. For example, miR-21 and miR-206 can effect on the tumor angiogenesis as an oncomir and a tumor suppressor, respectively.

MATERIALS AND METHODS

The present study is aimed to investigate the effects of the interval exercise training in combination with tamoxifen and/or letrozole on miR-21, miR-206 and let-7 as well as their underlying pathways in regard to tumor angiogenesis in sixty four mice with breast tumor. ELISA, immunohistochemistry, qRT-PCR assays were performed accomplish the study.

KEY FINDINGS

The results showed that the tumor size was significantly declined in the exercise training, tamoxifen and letrozole groups compared to tumor group. Mir-206 and let-7 were up-regulated, and mir-21 expression was down-regulated in the exercise training compared to tumor group. Exercise training decreased the expression of ER-α, HIF-α, VEGF, CD31 and Ki67 in tumor tissue. The combination tamoxifen and/or letrozole with the exercise training could down-regulate the expression of ERα, miR-21, HIF-1α, TNF-α, CD31, Ki67 and VEGF, and up-regulate the expression of miR-206, PDCD-4, let-7 and IL-10 that led to reducing the angiogenesis and tumor growth.

SIGNIFICANCE

Our results showed that miR-21, miR-206 and let-7a pathways may involve in the anti-angiogenesis effects of the interval exercise training with hormone therapy in mice model of breast tumor.