PPARγ-dependent pathway in the growth-inhibitory effects of K562 cells by carotenoids in combination with rosiglitazone

Astaxanthin decreases the growth-inhibitory dose of cytarabine and inflammatory response in the acute lymphoblastic leukemia cell line NALM-6

BACKGROUND

In spite of the great progress in acute lymphoblastic leukemia (ALL) treatment, a large number of patients still suffer from chemotherapy drug toxicity. As a routine medication for ALL treatment, cytarabine (Ara-C) has many side effects on the patients. Astaxanthin (ASX), on the other hand, is a carotenoid with antioxidant, anti-inflammatory and anti-cancer properties.

PURPOSE

The present study investigated the effects of ASX in combination with Ara-C on cell proliferation, apoptosis induction, and cell cycle arrest in NALM-6 cell line.

METHODS

NALM6 cells were treated with different concentrations of ASX, Ara-C, and their co-treatment. Cytotoxic effects were evaluated using MTT assay. After treating the cells with the IC50 dose of ASX, Ara-C and their co-treatment, we studied apoptosis induction, cell cycle arrest, and expression of apoptotic, anti-apoptotic, and inflammatory genes.

RESULT

MTT assay demonstrated that co-treatment of cytarabine and ASX had greater cytotoxicity effects compared with the IC50 dose of Ara-C alone. After 48 h of treatment of NALM-6 cells with the combination dose, expression levels of apoptotic genes (P53, caspase-8, 3), the anti-apoptotic gene (Bcl-xL) and inflammatory genes (IL-6, TNF-α) changed significantly compared to the untreated group (p < 0.05).

CONCLUSIONS

Co-treatment of ASX and Ara-C has synergism effects on apoptosis pathways, cell proliferation inhibition, and decreased inflammation.

Anti-Inflammatory and Anticancer Effects of Microalgal Carotenoids

Acute inflammation is a key component of the immune system’s response to pathogens, toxic agents, or tissue injury, involving the stimulation of defense mechanisms aimed to removing pathogenic factors and restoring tissue homeostasis. However, uncontrolled acute inflammatory response may lead to chronic inflammation, which is involved in the development of many diseases, including cancer. Nowadays, the need to find new potential therapeutic compounds has raised the worldwide scientific interest to study the marine environment. Specifically, microalgae are considered rich sources of bioactive molecules, such as carotenoids, which are natural isoprenoid pigments with important beneficial effects for health due to their biological activities. Carotenoids are essential nutrients for mammals, but they are unable to synthesize them; instead, a dietary intake of these compounds is required. Carotenoids are classified as carotenes (hydrocarbon carotenoids), such as α- and β-carotene, and xanthophylls (oxygenate derivatives) including zeaxanthin, astaxanthin, fucoxanthin, lutein, α- and β-cryptoxanthin, and canthaxanthin. This review summarizes the present up-to-date knowledge of the anti-inflammatory and anticancer activities of microalgal carotenoids both in vitro and in vivo, as well as the latest status of human studies for their potential use in prevention and treatment of inflammatory diseases and cancer.

Astaxanthin anticancer effects are mediated through multiple molecular mechanisms: A systematic review

During the latest decades, the interest on the effectiveness of natural compounds and their impact on human health constantly increased, especially on those demonstrating to be effective on cancer. Molecules coming from nature are currently used in chemotherapy like Taxol, Vincristine or Vinblastine, and several other natural substances have been showed to be active in reducing cancer cell progression and migration. Among them, astaxanthin, a xanthophyll red colored carotenoid, displayed different biological activities including, antinflammatory, antioxidant, proapoptotic, and anticancer effects. It can induce apoptosis through downregulation of antiapoptotic protein (Bcl-2, p-Bad, and survivin) expression and upregulation of proapoptotic ones (Bax/Bad and PARP). Thanks to these mechanisms, it can exert anticancer effects towards colorectal cancer, melanoma, or gastric carcinoma cell lines. Moreover, it possesses antiproliferative activity in many experimental models and enhances the effectiveness of conventional chemotherapic drugs on tumor cells underling its potential future use. This review provides an overview of the current knowledge on the anticancer potential of astaxanthin by modulating several molecular targets. While it has been clearly demonstrated its multitarget activity in the prevention and regression of malignant cells in in vitro or in preclinical investigations, further clinical studies are needed to assess its real potential as anticancer in humans.

New insights into molecular mechanisms of rosiglitazone in monotherapy or combination therapy against cancers

Rosiglitazone (ROSI), a member of thiazolidinediones (TZDs) which act as high-affinity agonists of the nuclear receptor peroxisome-proliferator-activated receptor-γ (PPARγ), is clinically used as an antidiabetic drug which could attenuate the insulin resistance associated with obesity, hypertension, and impaired glucose tolerance in humans. However, recent studies reported that ROSI had significant anticancer effects on various human malignant tumor cells. Mounting evidence indicated that ROSI could exert anticancer effects through PPARγ-dependent or PPARγ-independent ways. In this review, we summarized the PPARγ-dependent antitumor activities of ROSI, which included apoptosis induction, inhibition of cell proliferation and cancer metastasis, reversion of multidrug resistance, reduction of immune suppression, autophagy induction, and antiangiogenesis; and the PPARγ-independent antitumor activities of ROSI, which included inhibition of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway, inhibition of prostaglandin E2 (PGE₂), increasing MAPK phosphatase 1 (MKP-1) expression and regulation of other apoptosis-related cell factors. In addition, we discussed the anti-cancer application of ROSI by monotherapy or combination therapy with present chemotherapeutic drugs in vitro and in vivo. Moreover, we reviewed the phase I cancer clinical trials related to ROSI combined with chemotherapeutics and phase II trials about the anti-cancer effects of ROSI monotherapy and the radiotherapy sensitivity of ROSI.

Suppressive effects of lycopene and β-carotene on the viability of the human esophageal squamous carcinoma cell line EC109

The molecular mechanisms underlying the chemopreventive effects of carotenoids in different types of cancer are receiving increasing attention. In the present study, the role of peroxisome proliferator-activated receptor γ (PPARγ) in the effect of lycopene and β-carotene on the viability of EC109 human esophageal squamous carcinoma cells was investigated. The viability of EC109 cells was evaluated using MTT assays. The effects of lycopene and β-carotene on the expression of PPARγ, p21^WAF1/CIP1, cyclin D1 and cyclooxygenase-2 (COX-2) were analyzed by western blotting. Lycopene and β-carotene (5-40 µM) dose- and time-dependently reduced the viability of the EC109 cells. GW9662, an irreversible PPARγ antagonist, partly attenuated the decrease in EC109 cell viability induced by these carotenoids. Lycopene and β-carotene treatments upregulated the expression of PPARγ and p21^WAF1/CIP1, and downregulated the expression of cyclin D1 and COX-2. These modulatory effects of the carotenoid treatments were suppressed by GW9662, suggesting that the inhibition of EC109 cell viability by lycopene and β-carotene involves PPARγ signaling pathways and the modulation of p21^WAF1/CIP1, cyclin D1 and COX-2 expression.

The α-melanocyte stimulating hormone/peroxisome proliferator activated receptor-γ pathway down-regulates proliferation in melanoma cell lines

Background

The α-Melanocyte Stimulating Hormone (αMSH)/Melanocortin-1 receptor (MC1R) interaction promotes melanogenesis through the cAMP/PKA pathway. The direct induction of this pathway by Forskolin (FSK) is also known to enhance melanocyte proliferation. αMSH acts as a mitogenic agent in melanocytes and its effect on proliferation of melanoma cells is less known. We previously identified the αMSH/Peroxisome Proliferator Activated Receptor (PPARγ) pathway as a new pathway on the B16-F10 mouse melanoma cell line. αMSH induced the translocation of PPARγ into the nucleus as an active transcription factor. This effect was independent of the cAMP/PKA pathway and was mediated by the activation of the PI(4,5)P2/PLC pathway, a pathway which we have described to be triggered by the αMSH-dependent MC1R stimulation. Moreover, in the same study, preliminary experiments showed that mouse melanoma cells responded to αMSH by reducing proliferation and that PPARγ was involved in this effect. Due to its key role in the control of cell proliferation, PPARγ agonists are used in therapeutic models for different forms of cancer, including melanoma. The purpose of this study was: (a) to confirm the different proliferative behavior in response to αMSH in healthy and in melanoma condition; (b) to verify whether the cAMP/PKA pathway and the PLC/PPARγ pathway could exert an antagonistic function in the control of proliferation; (c) to deepen the knowledge of the molecular basis responsible for the down-proliferative response of melanoma cells after exposure to αMSH.

Methods

We employed B16-F10 cell line, a human melanoma cell line (Mel 13) and two primary cultures of human melanocytes (NHM 1 and NHM 2, respectively), all expressing a wild type MC1R and responding to the αMSH in terms of pigmentation. We evaluated cell proliferation through: a) cell counting, b) cell cycle analysis c) protein expression of proliferation modulators (p27, p21, cyclin D1 and cyclin E).

Results

The αMSH acted as a mitogenic agent in primary cultures of human melanocytes, whereas it determined a slow down of proliferation in melanoma cell lines. FSK, as an inducer of the cAMP/PKA pathway, reproduced the αMSH mediated effect on proliferation in NHMs but it did not mimic the αMSH effect on proliferation in B16-F10 and Mel 13 melanoma cell lines. Meanwhile, 3 M3-FBS (3 M3), as an inducer of PI(4,5)P2/PLC pathway, reproduced the αMSH proliferative effect. Further experiments, treating melanoma cell lines with αMSH in the presence/absence of GW9662, as an inhibitor of PPARγ, confirmed the key role of this transcription factor in decreasing cell proliferation in response to the hormone exposure.

Conclusions

In both melanoma cell lines, αMSH determined the reduction of proliferation through the PI(4,5)P2/PLC pathway, employing PPARγ as an effector element. These evidence could offer perspectives for new therapeutic approaches for melanoma.

Electronic supplementary material

The online version of this article (10.1186/s13046-017-0611-4) contains supplementary material, which is available to authorized users.

The role of pparγ and autophagy in ros production, lipid droplets biogenesis and its involvement with colorectal cancer cells modulation

Background

In cancer cells, autophagy can act as both tumor suppressor, when autophagic event eliminates cellular contends which exceeds the cellular capacity of regenerate promoting cell death, and as a pro-survival agent removing defective organelles and proteins and helping well-established tumors to maintain an accelerated metabolic state while still dealing with harsh conditions, such as inflammation. Many pathways can coordinate the autophagic process and one of them involves the transcription factors called PPARs, which also regulate cellular differentiation, proliferation and survival. The PPARγ activation and autophagy initiation seems to be interrelated in a variety of cell types.

Methods

Caco-2 cells were submitted to treatment with autophagy and PPARγ modulators and the relationship between both pathways was determined by western blotting and confocal microscopy. The effects of such modulations on Caco-2 cells, such as lipid bodies biogenesis, cell death, proliferation, cell cycle, ROS production and cancer stem cells profiling were analyzed by flow cytometry.

Results

PPARγ and autophagy pathways seem to be overlap in Caco-2 cells, modulating each other in different ways and determining the lipid bodies biogenesis. In general, inhibition of autophagy by 3-MA leaded to reduced cell proliferation, cell cycle arrest and, ultimately, cell death by apoptosis. In agreement with these results, ROS production was increased in 3-MA treated cells. Autophagy also seems to play an important role in cancer stem cells profiling. Rapamycin and 3-MA induced epithelial and mesenchymal phenotypes, respectively.

Conclusions

This study helps to elucidate in which way the induction or inhibition of these pathways regulate each other and affect cellular properties, such as ROS production, lipid bodies biogenesis and cell survive. We also consolidate autophagy as a key factor for colorectal cancer cells survival in vitro, pointing out a potential side effect of autophagic inhibition as a therapeutic application for this disease and demonstrate a novel regulation of PPARγ expression by inhibition of PI3K III.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-017-0451-5) contains supplementary material, which is available to authorized users.

β-Carotene synergistically enhances the anti-tumor effect of 5-fluorouracil on esophageal squamous cell carcinoma in vivo and in vitro

Recently, we reported that β-carotene exhibited anticancer activity against human esophageal squamous cell carcinoma cells in vitro. In the present study, we examined a novel therapeutic strategy by combining β-carotene with 5-fluorouracil (5-FU) in human esophageal cancer in vitro and in vivo, and elucidated the underlying mechanisms. We found that the combination of 5-FU and β-carotene displayed greater growth inhibitory effects than did either compound alone in esophageal squamous cell carcinoma (ESCC) cells. In addition, the combination of 5-FU and β-carotene displayed greater tumor growth inhibition in an Eca109 xenograft mouse model than did a single agent with low systemic toxicity. β-Carotene enhanced 5-FU-induced apoptosis. TUNEL staining revealed that the rate of TUNEL-positive cells was markedly increased in tumor tissues after treatment with 5-FU and β-carotene. Western blotting and immunohistochemistry revealed the down-regulation of Bcl-2 and PCNA and the up-regulation of Bax and caspase-3 in tumor tissues. Further studies demonstrated that the combined administration of 5-FU and β-carotene significantly down-regulated the protein levels of Cav-1, p-AKT, p-NF-κB, p-mTOR and p-p70S6K in Eca109 cells more effectively than did 5-FU alone. These data suggested that the combined therapy of 5-FU and β-carotene exerted synergistic antitumor effects in vivo and in vitro and could constitute a novel therapeutic treatment for ESCC.