Clinical Significance of the Wild Type p53-Induced Phosphatase 1 Expression in Invasive Breast Cancer

PP2C phosphatases-terminators of suicidal thoughts

Cell death and related signaling pathways are essential during development and in various physiological and pathological conditions. Post-translational modifications such as ubiquitination and phosphorylation play an important role in these signaling pathways. The involvement of kinases - enzymes that catalyze protein phosphorylation - in cell death signaling has been extensively studied. On the other hand, not many studies have been devoted to analyzing the role in cell death of phosphatases, enzymes involved in the removal of phosphorylated residues added to proteins by kinases. Obviously, the two opposite reactions, phosphorylation and dephosphorylation, are equally important in the regulation of protein functions and subsequently in the execution of the cell death program. Here, we have summarized recent work on the involvement of serine-threonine PP2C phosphatases in cell death pathways, senescence and autophagy, focusing in particular on the most studied phosphatase PPM1D (PP2Cδ) as an example of the regulatory role of PP2Cs in cell death. The review should help to draw attention to the importance of PP2C family phosphatases in cell death checkpoints and to discover new targets for drug development.

Investigation of HER-3 gene expression under the influence of carbohydrate biopolymers extract of shiitake and reishi in MCF-7 cell line

INTRODUCTION

Edible-medicinal fungi are mainly used in Asian countries to prevent various diseases. These mushrooms are also used to treat lung diseases and cancer. Ganoderma lucidum and Lentinula edodes are the most important edible-medicinal fungi. The polysaccharides of these fungi are one of the bioactive compounds with anti-cancer properties.

OBJECTIVE

Evaluation of anti-cancer effects of Shiitake and Reishi polysaccharides.

METHODS

In this study, fungal polysaccharides were extracted using the hot water method and were purified by Diethylaminoethyl Sephadex A-25 (DEAE-Sephadex A-25) chromatography column and their concentration was measured by phenolic sulfuric acid method. The biological effects of the extracted polysaccharides from Ganoderma lucidum and Lentinula edodes on the MCF-7 cell line were investigated using an MTT assay and then its effects on the expression of the P53 cancer regulatory gene and HER-3 gene were investigated.

RESULTS

Based on the results, the concentration of Ganoderma lucidum and Lentinula edodes extracted polysaccharides were 0.024 and 0.103 mg/ml, respectively. Polysaccharides of these two fungi increased the expression of the P53 gene and decreased the expression of the HER-3 gene in a dose and time-dependent manner.

DISCUSSION

Natural biocompatible polysaccharides with anti-cancer properties that are native, are available, and inexpensive, so they can be used as dietary supplements to prevent and help treat cancer.

Phosphatase magnesium-dependent 1 δ (PPM1D), serine/threonine protein phosphatase and novel pharmacological target in cancer

Aberrations in DNA damage response genes are recognized mediators of tumorigenesis and resistance to chemo- and radiotherapy. While protein phosphatase magnesium-dependent 1 δ (PPM1D), located on the long arm of chromosome 17 at 17q22-23, is a key regulator of cellular responses to DNA damage, amplification, overexpression, or mutation of this gene is important in a wide range of pathologic processes. In this review, we describe the physiologic function of PPM1D, as well as its role in diverse processes, including fertility, development, stemness, immunity, tumorigenesis, and treatment responsiveness. We highlight both the advances and limitations of current approaches to targeting malignant processes mediated by pathogenic alterations in PPM1D with the goal of providing rationale for continued research and development of clinically viable treatment approaches for PPM1D-associated diseases.

Model-based optimization of combination protocols for irradiation-insensitive cancers

Alternations in the p53 regulatory network may render cancer cells resistant to the radiation-induced apoptosis. In this theoretical study we search for the best protocols combining targeted therapy with radiation to treat cancers with wild-type p53, but having downregulated expression of PTEN or overexpression of Wip1 resulting in resistance to radiation monotherapy. Instead of using the maximum tolerated dose paradigm, we exploit stochastic computational model of the p53 regulatory network to calculate apoptotic fractions for both normal and cancer cells. We consider combination protocols, with irradiations repeated every 12, 18, 24, or 36 h to find that timing between Mdm2 inhibitor delivery and irradiation significantly influences the apoptotic cell fractions. We assume that uptake of the inhibitor is higher by cancer than by normal cells and that cancer cells receive higher irradiation doses from intersecting beams. These two assumptions were found necessary for the existence of protocols inducing massive apoptosis in cancer cells without killing large fraction of normal cells neighboring tumor. The best found protocols have irradiations repeated every 24 or 36 h with two inhibitor doses per irradiation cycle, and allow to induce apoptosis in more than 95% of cancer cells, killing less than 10% of normal cells.

The role of PPM1D in cancer and advances in studies of its inhibitors

A greater understanding of factors causing cancer initiation, progression and evolution is of paramount importance. Among them, the serine/threonine phosphatase PPM1D, also referred to as wild-type p53-induced phosphatase 1 (Wip1) or protein phosphatase 2C delta (PP2Cδ), is emerging as an important oncoprotein due to its negative regulation on a number of crucial cancer suppressor pathways. Initially identified as a p53-regulated gene, PPM1D has been afterwards found amplified and more recently mutated in many human cancers such as breast cancer. The latest progress in this field further reveals that selective inhibition of PPM1D to delay tumor onset or reduce tumor burden represents a promising anti-cancer strategy. Here, we review the advances in the studies of the PPM1D activity and its relevance to various cancers, and recent progress in development of PPM1D inhibitors and discuss their potential application in cancer therapy. Consecutive research on PPM1D and its relationship with cancer is essential, as it ultimately contributes to the etiology and treatment of cancer.

Wip1 cooperates with KPNA2 to modulate the cell proliferation and migration of colorectal cancer via a p53-dependent manner

Due to the increasing incidence and mortality, the early diagnosis, specific targeted therapies, and prognosis for colorectal cancer (CRC) attract more and more attention. Wild-type p53-induced phosphatase 1 (Wip1) and karyopherin α2 (KPNA2) have been regarded as oncogenes in many cancers, including CRC. Wip1 dephosphorylates p53 to inactivate it. TP53 activator and Wip1 inhibitor downregulate KPNA2 expression. Therefore, we speculate that Wip1 may co-operate with KPNA2 to modulate CRC progression in a p53-dependent manner. Here, Wip1 and KPNA2 messenger RNA expression and protein levels are significantly increased in CRC tissues and cell lines and are positively correlated with each other. Wip1 silence increases p53 phosphorylation while decreases KPNA2 protein. Wip1 knockdown remarkably suppresses CRC cell proliferation and migration while KPNA2 overexpression exerts an opposing effect. KPNA2 overexpression could partially rescue Wip1 silence-inhibited CRC cell proliferation and migration. Finally, Wip1 interacts with KPNA2 to modulate the activation of AKT/GSK-3β signaling and metastasis-related factors. In summary, Wip1 could co-operate with KPNA2 to modulate CRC cell proliferation and migration, possibly via a p53-dependent manner, through downstream AKT/GSK-3β pathway. We provided a novel mechanism of Wip1 interacting with KPNA2, therefore modulating CRC cell proliferation and migration.