Activation of peroxisome proliferator-activated receptor gamma in mammary epithelial cells upregulates the expression of tumor suppressor Cyld to mediate growth inhibition and anti-inflammatory effects

Peroxisome Proliferator-Activated Receptors and the Hallmarks of Cancer

Peroxisome proliferator-activated receptors (PPARs) function as nuclear transcription factors upon the binding of physiological or pharmacological ligands and heterodimerization with retinoic X receptors. Physiological ligands include fatty acids and fatty-acid-derived compounds with low specificity for the different PPAR subtypes (alpha, beta/delta, and gamma). For each of the PPAR subtypes, specific pharmacological agonists and antagonists, as well as pan-agonists, are available. In agreement with their natural ligands, PPARs are mainly focused on as targets for the treatment of metabolic syndrome and its associated complications. Nevertheless, many publications are available that implicate PPARs in malignancies. In several instances, they are controversial for very similar models. Thus, to better predict the potential use of PPAR modulators for personalized medicine in therapies against malignancies, it seems necessary and timely to review the three PPARs in relation to the didactic concept of cancer hallmark capabilities. We previously described the functions of PPAR beta/delta with respect to the cancer hallmarks and reviewed the implications of all PPARs in angiogenesis. Thus, the current review updates our knowledge on PPAR beta and the hallmarks of cancer and extends the concept to PPAR alpha and PPAR gamma.

The Tumor Suppressor CYLD Inhibits Mammary Epithelial to Mesenchymal Transition by the Coordinated Inhibition of YAP/TAZ and TGF Signaling

Downregulation of the cylindromatosis (CYLD) tumor suppressor has been associated with breast cancer development and progression. Here, we report a critical role for CYLD in maintaining the phenotype of mammary epithelial cells in vitro and in vivo. CYLD downregulation or inactivation induced an epithelial to mesenchymal transition of mammary epithelial cells that was dependent on the concomitant activation of the transcription factors Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) and transforming growth factor beta (TGF)signaling. CYLD inactivation enhanced the nuclear localization of YAP/TAZ and the phosphorylation of Small Mothers Against Decapentaplegic (SMAD)2/3 proteins in confluent cell culture conditions. Consistent with these findings were the hyperplastic alterations of CYLD-deficient mouse mammary epithelia, which were associated with enhanced nuclear expression of the YAP/TAZ transcription factors. Furthermore, in human breast cancer samples, downregulation of CYLD expression correlates with enhanced YAP/TAZ-regulated target gene expression. Our results identify CYLD as a critical regulator of a signaling node that prevents the coordinated activation of YAP/TAZ and the TGF pathway in mammary epithelial cells, in order to maintain their phenotypic identity and homeostasis. Consequently, they provide a novel conceptual framework that supports and explains a causal implication of deficient CYLD expression in aggressive human breast cancers.

Marie Unna hereditary hypotrichosis accompanied by multiple familial trichoepithelioma in a Chinese family

Marie Unna hereditary hypotrichosis (MUHH) and multiple familial trichoepithelioma (MFT) are both autosomal dominant disorders. Recently, certain genes (HR and EPS8L3) have been found to be responsible for MUHH, while CYLD has been demonstrated to be the main pathogenic gene in MFT patients. However, there exist a number of CYLD mutation-negative MFT cases, for which the causative gene has been unknown. Here, we identified a large, five-generation Han Chinese family with several patients presenting with MUHH and MFT. Sanger sequencing of three genes in 13 family members was performed. We found that the c.1A>G mutation in an inhibitory upstream open-reading frame of HR (U2HR) was present in all MUHH patients, while no pathogenic variants were found in the 3'- or 5'-untranslated regions, exons or flanking intronic sequences of EPS8L3 or CYLD in any family members. Subsequently, whole-genome sequencing was performed for five affected and one unaffected family member. We found no CYLD variants but identified an FABP12 variant (rs536105592 G>A) in the patients with both MUHH and MFT. These results suggest that the U2HR mutation was responsible for MUHH and the FABP12 variant may be coincidental in the accompanying MFT in this unique pedigree. This report deepens our understanding of the genetic basis of hair follicle diseases.

Adding Oral Pioglitazone to Standard Induction Chemotherapy of Acute Myeloid Leukemia: A Randomized Clinical Trial

BACKGROUND

The hypothesis of an effect by thiazolidinedione on leukemia cells was proposed 2 decades ago, but there is little clinical evidence regarding its efficacy. We evaluated the safety and efficacy of adding pioglitazone to standard induction chemotherapy in patients with acute myeloid leukemia (AML).

PATIENTS AND METHODS

In this randomized clinical trial, newly diagnosed AML patients were randomized to 1 of 2 groups. Patients in both groups received cytarabine (100 mg/m² per day for 7 days) and daunorubicin (60 mg/m² per day for 3 days). Patients in the pioglitazone group additionally received oral pioglitazone (45 mg per day). The 2 groups were compared according to remission rate, laboratory findings, and adverse events during treatment.

RESULTS

Forty patients were evaluated, 20 patients in each group. The complete remission rate was 20% more in the pioglitazone group compared to the control group (P = .202). Complications due to pioglitazone discontinuation were observed in 2 cases. The mean serum alanine aminotransferase in the fourth treatment week was significantly more in pioglitazone group compared to the control group (65.5 vs. 33.6 mg/dL, P = .039). The mean serum creatinine in all treatment phases was significantly higher in the pioglitazone group compared to the control group (P < .05). There were no significant differences between the 2 groups regarding other laboratory findings (P > .05).

CONCLUSION

Adding pioglitazone to cytarabine and daunorubicin increased the remission rate in AML patients compared to control subjects. Although this difference in remission rate between the 2 groups was not statistically significant, it could be important in the clinical setting. Pioglitazone may provide benefits as an adjuvant therapy for AML patients without causing serious adverse events.

CLA-supplemented diet accelerates experimental colorectal cancer by inducing TGF-β-producing macrophages and T cells

Conjugated linoleic acid (CLA) has been shown to activate the nuclear receptor PPAR-γ and modulate metabolic and immune functions. Despite the worldwide use of CLA dietary supplementation, strong scientific evidence for its proposed beneficial actions are missing. We found that CLA-supplemented diet reduced mucosal damage and inflammatory infiltrate in the dextran sodium sulfate (DSS)-induced colitis model. Conditional deletion of PPAR-γ in macrophages from mice supplemented with CLA diet resulted in loss of this protective effect of CLA, suggesting a PPAR-γ-dependent mechanism mediated by macrophages. However, CLA supplementation significantly worsened colorectal tumor formation induced by azoxymethane and DSS by inducing macrophage and T-cell-producing TGF-β via PPAR-γ activation. Accordingly, either macrophage-specific deletion of PPAR-γ or in vivo neutralization of latency-associated peptide (LAP, a membrane-bound TGF-β)-expressing cells abrogated the protumorigenic effect of CLA. Thus, the anti-inflammatory properties of CLA are associated with prevention of colitis but also with development of colorectal cancer.

Peroxisome Proliferator-Activated Receptor γ and PGC-1α in Cancer: Dual Actions as Tumor Promoter and Suppressor

Peroxisome proliferator-activated receptor γ (PPARγ) is part of a nuclear receptor superfamily that regulates gene expression involved in cell differentiation, proliferation, immune/inflammation response, and lipid metabolism. PPARγ coactivator-1α (PGC-1α), initially identified as a PPARγ-interacting protein, is an important regulator of diverse metabolic pathways, such as oxidative metabolism and energy homeostasis. The role of PGC-1α in diabetes, neurodegeneration, and cardiovascular disease is particularly well known. PGC-1α is also now known to play important roles in cancer, independent of the role of PPARγ in cancer. Though many researchers have studied the expression and clinical implications of PPARγ and PGC-1α in cancer, there are still many controversies about the role of PPARγ and PGC-1α in cancer. This review examines and summarizes some recent data on the role and action mechanisms of PPARγ and PGC-1α in cancer, respectively, particularly the recent progress in understanding the role of PPARγ in several cancers since our review was published in 2012.