Epigenetic mechanisms of DNA methylation in the transgenerational effect of ethylhexyl salicylate on zebrafish

In this study, a 120-day whole-life cycle exposure and oviposition experiment on zebrafish with maternal and paternal mixed mating strategy was conducted to investigate the epigenetic mechanism of DNA methylation in ethylhexyl salicylate (EHS, 1, 10, 100 μg/L)-induced transgenerational effects. Results showed that EHS could induce the decrease of DNA methyltransferase 1 (DNMT1) activity and average global DNA methylation level in maternal parents and the increase of the above indexes in paternal parents, while the change of glycine N-methyltransferase activity was opposite to DNMT1. The average global DNA methylation levels were significantly increased in the offsprings of both parents exposed and father-only exposed to EHS, suggesting that EHS-induced epigenetic modifications may be stable and heritable. Hierarchical clustering analysis of promoter at different methylation sites showed that the DNA methylation pattern of offsprings were similar to that of the paternal parents, meaning that the offsprings may have inherited paternal DNA methylation pattern with eya2, pcdh2g5 and pcdh2g1 as key genes and lead to high locomotor activity in offsprings. KEGG pathway analysis showed that parental exposure to EHS may interfere with the central nervous system, insulin function system, melanogenesis system and the normal development of somatic axis of offsprings.

Cancer cell line microarray as a novel screening method for identification of radioresistance biomarkers in head and neck squamous cell carcinoma

Background

Currently, no clinically useful biomarkers for radioresistance are available in head and neck squamous cell carcinoma (HNSCC). This study assesses the usefulness of Cell Line Microarray (CMA) method to enhance immunohistochemical screening of potential immunohistochemical biomarkers for radioresistance in HNSCC cell lines.

Methods

Twenty-nine HNSCC cell lines were cultured, cell pellets formalin-fixed, paraffin-embedded, and arrayed. Radioresistance features of the cell lines were combined to immunohistochemical stains for p53, NDFIP1, EGFR, stem cell marker Oct4, and PP2A inhibitor CIP2A.

Results

Expression of p53, EGFR or CIP2A did not indicate intrinsic radioresistance in vitro. Stem cell marker Oct4 nuclear positivity and NDFIP1 nuclear positivity was correlated with increased intrinsic radioresistance.

Conclusion

The usefulness of CMA in analysis of HNSCC cell lines and discovery of biomarkers is demonstrated. CMA is very well adapted to both testing of antibodies in a large panel of cell lines as well as correlating staining results with other cell line characteristics. In addition, CMA-based antibody screening proved an efficient and relatively simple method to identify potential radioresistance biomarkers in HNSCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08618-6.

The interaction of SET and protein phosphatase 2A as target for cancer therapy

In cancer cells, tumor suppressor proteins loss-of-function are usually the result of genetic mutations. Protein Phosphatase 2A is a tumor suppressor that inactivates several signaling pathways through removal of phosphate residues important for other proteins stability and/or activation. Different from other tumor suppressors, PP2A is, in many cancer types, inactivated by endogenous inhibitors. In physiological conditions, these inhibitors are important to balance PP2A activity. However, in cancer cells, overexpression of these inhibitors can keep PP2A inactive, resulting in sustained activation of mitogenic signaling pathways and transcription factors, metabolic reprogramming, with the resulting cancer progression and the resistance to anti-cancer therapies. One of these endogenous inhibitors is the protein SET (SE Translocation). SET is a multifunctional protein, which high expression has been associated with several types of cancer, as well as other diseases such as Alzheimer's disease. Disruption of the interaction between SET and PP2A to rescue the activity of PP2A may represent a new therapeutic strategy and opportunity for cancer treatment. This review brings up-to-date advances on the interactions between SET and PP2A and their biological consequences. Moreover, we review reported inhibitors of SET-PP2A interaction under investigation as therapeutic opportunities for the treatment of cancers.

CIP2A silencing alleviates doxorubicin resistance in MCF7/ADR cells through activating PP2A and autophagy

Background

Cancerous inhibitor of protein phosphatase 2A (CIP2A) plays a critical role in the pathogenesis of various types of cancer. Here, we investigated whether manipulating CIP2A abundance could enhance the treatment effects of doxorubicin in MCF-7/ADR cells.

Methods

CIP2A silencing was achieved by specific siRNAs. Proliferation of breast cancer cell line MCF-7/ADR under effective doxorubicin concentrations after CIP2A silencing was examined by MTT assay. Wound healing assay was performed to quantify cell migration and caspase-3/-7 activities were measured for assessing the extent of apoptosis.

Results

First, our data confirmed that MCF-7/ADR cell proliferation was suppressed by doxorubicin in a dose-dependent manner. Additionally, knocking down of CIP2A could further decrease MCF-7 cell proliferation and migration, even in the presence of doxorubicin. Mechanistically, we have found that CIP2A silencing promoted cell apoptosis relative to doxorubicin alone or vehicle control groups. Lastly, phosphatase2A (PP2A) activity was potentiated and the autophagy markers, LC3B and Beclin1, were upregulated after knocking down CIP2A.

Conclusion

Our findings support the potential benefits of using CIP2A inhibitor as a therapeutic agent to treat doxorubicin-resistant breast cancer.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12094-021-02616-7.

PP2A inhibition is a druggable MEK inhibitor resistance mechanism in KRAS-mutant lung cancer cells

Kinase inhibitor resistance constitutes a major unresolved clinical challenge in cancer. Furthermore, the role of serine/threonine phosphatase deregulation as a potential cause for resistance to kinase inhibitors has not been thoroughly addressed. We characterize protein phosphatase 2A (PP2A) activity as a global determinant of KRAS-mutant lung cancer cell resistance across a library of >200 kinase inhibitors. The results show that PP2A activity modulation alters cancer cell sensitivities to a large number of kinase inhibitors. Specifically, PP2A inhibition ablated mitogen-activated protein kinase kinase (MEK) inhibitor response through the collateral activation of AKT/mammalian target of rapamycin (mTOR) signaling. Combination of mTOR and MEK inhibitors induced cytotoxicity in PP2A-inhibited cells, but even this drug combination could not abrogate MYC up-regulation in PP2A-inhibited cells. Treatment with an orally bioavailable small-molecule activator of PP2A DT-061, in combination with the MEK inhibitor AZD6244, resulted in suppression of both p-AKT and MYC, as well as tumor regression in two KRAS-driven lung cancer mouse models. DT-061 therapy also abrogated MYC-driven tumorigenesis. These data demonstrate that PP2A deregulation drives MEK inhibitor resistance in KRAS-mutant cells. These results emphasize the need for better understanding of phosphatases as key modulators of cancer therapy responses.

Potential anti-tumor effects of FTY720 associated with PP2A activation: a brief review

FTY720 (Fingolimod, Gilenya (†) ) is an FDA-approved immunosuppressant currently used in the treatment of multiple sclerosis. However, a large number of studies over the last few years have shown that FTY720 shows potent antitumor properties that suggest its potential usefulness as a novel anticancer agent. Interestingly, the restoration of protein phosphatase 2A (PP2A) activity mediated by FTY720 could play a key role in its antitumor effects. Taking into account that PP2A inactivation is a common event that determines poor outcome in several tumor types, FTY720 could serve as an alternative therapeutic strategy for cancer patients with such alterations.