Modulation of glycogen synthase kinase-3β following TRAIL combinatorial treatment in cancer cells

PPARγ Agonists in Combination Cancer Therapies

Peroxisome proliferator-activated receptor-gamma (PPARγ) is a nuclear receptor acting as a transcription factor involved in the regulation of energy metabolism, cell cycle, cell differentiation, and apoptosis. These unique properties constitute a strong therapeutic potential that place PPARγ agonists as one of the most interesting and widely studied anticancer molecules. Although PPARγ agonists exert significant, antiproliferative and tumoricidal activity in vitro, their anticancer efficacy in animal models is ambiguous, and their effectiveness in clinical trials in monotherapy is unsatisfactory. However, due to pleiotropic effects of PPARγ activation in normal and tumor cells, PPARγ ligands interact with many antitumor treatment modalities and synergistically potentiate their effectiveness. The most spectacular example is a combination of PPARγ ligands with tyrosine kinase inhibitors (TKIs) in chronic myeloid leukemia (CML). In this setting, PPARγ activation sensitizes leukemic stem cells, resistant to any previous form of treatment, to targeted therapy. Thus, this combination is believed to be the first pharmacological therapy able to cure CML patients. Within the last decade, a significant body of data confirming the benefits of the addition of PPARγ ligands to various antitumor therapies, including chemotherapy, hormonotherapy, targeted therapy, and immunotherapy, has been published. Although the majority of these studies have been carried out in vitro or animal tumor models, a few successful attempts to introduce PPARγ ligands into anticancer therapy in humans have been recently made. In this review, we aim to summarize shines and shadows of targeting PPARγ in antitumor therapies.

Crosstalk between the Androgen Receptor and PPAR Gamma Signaling Pathways in the Prostate

Nuclear receptors are a superfamily of ligand-activated transcription factors that play critical roles in the regulation of normal biological processes and several disease states. Of the nuclear receptors expressed within the prostate, the androgen receptor (AR) promotes the differentiation of prostatic epithelial cells and stimulates production of enzymes needed for liquefaction of semen. Multiple forms of AR also promote the growth of both early and late stage prostate cancers. As a result, drugs that target the AR signaling pathway are routinely used to treat patients with advanced forms of prostate cancer. Data also suggest that a second member of the nuclear receptor superfamily, the peroxisome proliferator activated receptor gamma (PPARγ), is a tumor suppressor that regulates growth of normal prostate and prostate cancers. Recent studies indicate there is a bidirectional interaction between AR and PPARγ, with each receptor influencing the expression and/or activity of the other within prostatic tissues. In this review, we examine how AR and PPARγ each regulate the growth and development of normal prostatic epithelial cells and prostate cancers. We also discuss interactions between the AR and PPARγ signaling pathways and how those interactions may influence prostate biology.