Ligand-activated peroxisome proliferator-activated receptor β/δ modulates human endometrial cancer cell survival

The Role of Peroxisome Proliferator-Activated Receptors in Endometrial Cancer

Endometrial carcinoma is the most common malignant tumor of the female genital tract in the United States. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptor proteins which regulate gene expression. In order to investigate the role of PPARs in endometrial cancer, we conducted a literature review using the MEDLINE and LIVIVO databases and were able to identify 27 relevant studies published between 2000 and 2023. The PPARα and PPARβ/δ isoforms seemed to be upregulated, whereas PPARγ levels were reported to be significantly lower in endometrial cancer cells. Interestingly, PPAR agonists were found to represent potent anti-cancer therapeutic alternatives. In conclusion, PPARs seem to play a significant role in endometrial cancer.

Regulatory mechanisms mediated by peroxisome proliferator-activated receptor-β/δ in skin cancer

Considerable progress has been made during the past 20 years towards elucidating the role of peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) in skin cancer. In 1999, the original notion that PPARβ/δ was involved with epithelial cell function was postulated based on a correlation between PPARβ/δ expression and the induction of messenger RNAs encoding proteins that mediate terminal differentiation in keratinocytes. Subsequent studies definitively revealed that PPARβ/δ could induce terminal differentiation and inhibit proliferation of keratinocytes. Molecular mechanisms have since been discovered to explain how this nuclear receptor can be targeted for preventing and treating skin cancer. This includes the regulation of terminal differentiation, mitotic signaling, endoplasmic reticulum stress, and cellular senescence. Interestingly, the effects of activating PPARβ/δ can preferentially target keratinocytes with genetic mutations associated with skin cancer. This review provides the history and current understanding of how PPARβ/δ can be targeted for both nonmelanoma skin cancer and melanoma and postulates how future approaches that modulate PPARβ/δ signaling may be developed for the prevention and treatment of these diseases.

Apoptotic effect of the selective PPARβ/δ agonist GW501516 in invasive bladder cancer cells

GW501516 is a selective and high-affinity synthetic agonist of peroxisome proliferator-activated receptor β/δ (PPARβ/δ). This molecule promoted the inhibition of proliferation and apoptosis in few cancer cell lines, but its anticancer action has never been investigated in bladder tumor cells. Thus, this study was undertaken to determine whether GW501516 had antiproliferative and/or apoptotic effects on RT4 and T24 urothelial cancer cells and to explore the molecular mechanisms involved. Our results indicated that, in RT4 cells (derived from a low-grade papillary tumor), GW501516 did not induce cell death. On the other hand, in T24 cells (derived from an undifferentiated high-grade carcinoma), this PPARβ/δ agonist induced cytotoxic effects including cell morphological changes, a decrease of cell viability, a G2/M cell cycle arrest, and the cell death as evidenced by the increase of the sub-G1 cell population. Furthermore, GW501516 triggered T24 cell apoptosis in a caspase-dependent manner including both extrinsic and intrinsic apoptotic pathways through Bid cleavage. In addition, the drug led to an increase of the Bax/Bcl-2 ratio, a mitochondrial dysfunction associated with the dissipation of ΔΨm, and the release of cytochrome c from the mitochondria to the cytosol. GW501516 induced also ROS generation which was not responsible for T24 cell death since NAC did not rescue cells upon PPARβ/δ agonist exposure. For the first time, our data highlight the capacity of GW501516 to induce apoptosis in invasive bladder cancer cells. This molecule could be relevant as a therapeutic drug for high-grade urothelial cancers.

The role of PPARγ-mediated signalling in skin biology and pathology: new targets and opportunities for clinical dermatology

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that modulate the expression of multiple different genes involved in the regulation of lipid, glucose and amino acid metabolism. PPARs and cognate ligands also regulate important cellular functions, including cell proliferation and differentiation, as well as inflammatory responses. This includes a role in mediating skin and pilosebaceous unit homoeostasis: PPARs appear to be essential for maintaining skin barrier permeability, inhibit keratinocyte cell growth, promote keratinocyte terminal differentiation and regulate skin inflammation. They also may have protective effects on human hair follicle (HFs) epithelial stem cells, while defects in PPARγ-mediated signalling may promote the death of these stem cells and thus facilitate the development of cicatricial alopecia (lichen planopilaris). Overall, however, selected PPARγ modulators appear to act as hair growth inhibitors that reduce the proliferation and promote apoptosis of hair matrix keratinocytes. The fact that commonly prescribed PPARγ-modulatory drugs of the thiazolidine-2,4-dione class can exhibit a battery of adverse cutaneous effects underscores the importance of distinguishing beneficial from clinically undesired cutaneous activities of PPARγ ligands and to better understand on the molecular level how PPARγ-regulated cutaneous lipid metabolism and PPARγ-mediated signalling impact on human skin physiology and pathology. Surely, the therapeutic potential that endogenous and exogenous PPARγ modulators may possess in selected skin diseases, ranging from chronic inflammatory hyperproliferative dermatoses like psoriasis and atopic dermatitis, via scarring alopecia and acne can only be harnessed if the complexities of PPARγ signalling in human skin and its appendages are systematically dissected.

Expression profile of long non-coding RNAs is altered in endometrial cancer

This study was to uncover the role of long non-coding RNA (lncRNA) in the process of endometrial cancer (EC) development using microarray technique to obtain the expression profiles of lncRNAs in EC and its adjacent normal tissues. A total of 45 pieces of pathologically-proven EC tissues were used in this study. All samples were frozen in liquid nitrogen immediately after resection and stored at -80°C for future use. The detection of lncRNA and transcripts was conducted using microarray analysis. To understand the biochemical function of lncRNA, bioinformatics analyses (gene ontology and pathway analyses) were performed. To further investigate the relationship between lncRNAs and EC, subgroup analysis was conducted. In order to validate the consistency of the lncRNAs with microarray data, qRT-PCR was performed. In this study, 30586 lncRNAs and 26109 transcripts (fold change ≥ 2.0) were found in the tested EC. In particular, compared with normal tissues, 4010 the lncRNA were up-regulated, and 3350 of them were down-regulated. Seven of the lncRNAs were in accordance with microarray data in qRT-PCR. Among these lncRNAs, 3 were up-regulated and 4 were down-regulated. Furthermore, pathway analysis revealed that 24 pathways were correlated to the up-regulated transcripts, while 27 pathways were associated with the down-regulated transcripts. Our study demonstrated that the expressions of a large amount of lncRNAs were altered in EC in comparison to normal tissues, suggesting that lncRNAs could potentially serve as a diagnostic biomarker that is beneficial for the diagnosis and therapy of EC.

Fenretinide: a novel treatment for endometrial cancer

Resistance to progestin treatment is a major hurdle in the treatment of advanced and reoccurring endometrial cancer. Fenretinide is a synthetic retinoid that has been evaluated in clinical trials as a cancer therapeutic and chemo-preventive agent. Fenretinide has been established to be cytotoxic to many kinds of cancer cells. In the present study, we demonstrate that fenretinide decreased cell viability and induced apoptosis in Ishikawa cells, which are an endometrial cancer cell line, in dose dependent manner in-vitro. This effect was found to be independent of retinoic acid nuclear receptor signaling pathway. Further, we have shown that this induction of apoptosis by fenretinide may be caused by increased retinol uptake via STRA6. Silencing of STRA6 was shown to decrease apoptosis which was inhibited by knockdown of STRA6 expression in Ishikawa cells. Results of an in-vivo study demonstrated that intraperitoneal injections of fenretinide in endometrial cancer tumors (created using Ishikawa cells) in mice inhibited tumor growth effectively. Immunohistochemistry of mice tumors showed a decrease in Ki67 expression and an increase in cleaved caspase-3 staining after fenretinide treatment when compared to vehicle treated mice. Collectively, our results are the first to establish the efficacy of fenretinide as an antitumor agent for endometrial cancer both in-vitro and in-vivo, providing a valuable rationale for initiating more preclinical studies and clinical trials using fenretinide for the treatment of endometrial cancer.