Protein phosphatase 2A (PP2A) inhibitor CIP2A indicates resistance to radiotherapy in rectal cancer

From Basic Science to Clinical Practice: The Role of Cancerous Inhibitor of Protein Phosphatase 2A (CIP2A)/p90 in Cancer

Cancerous inhibitor of protein phosphatase 2A (CIP2A), initially reported as a tumor-associated antigen (known as p90), is highly expressed in most solid and hematological tumors. The interaction of CIP2A/p90, protein phosphatase 2A (PP2A), and c-Myc can hinder the function of PP2A toward c-Myc S62 induction, thus stabilizing c-Myc protein, which represents a potential role of CIP2A/p90 in tumorigeneses such as cell proliferation, invasion, and migration, as well as cancer drug resistance. The signaling pathways and regulation networks of CIP2A/p90 are complex and not yet fully understood. Many previous studies have also demonstrated that CIP2A/p90 can be used as a potential therapeutic cancer target. In addition, the autoantibody against CIP2A/p90 in sera may be used as a promising biomarker in the diagnosis of certain types of cancer. In this Review, we focus on recent advances relating to CIP2A/p90 and their implications for future research.

The Pivotal Role of Protein Phosphatase 2A (PP2A) in Brain Tumors

Protein phosphatase 2A (PP2A) is a highly complex heterotrimeric Ser/Thr phosphatase that regulates many cellular processes. PP2A is dysregulated in several human diseases, including oncological pathology; interestingly, PP2A appears to be essential for controlling cell growth and may be involved in cancer development. The role of PP2A as a tumor suppressor has been extensively studied and reviewed. To leverage the potential clinical utility of combination PP2A inhibition and radiotherapy treatment, it is vital that novel highly specific PP2A inhibitors be developed. In this review, the existing literature on the role of PP2A in brain tumors, especially in gliomas and glioblastoma (GBM), was analyzed. Interestingly, the review focused on the role of PP2A inhibitors, focusing on CIP2A inhibition, as CIP2A participated in tumor cell growth by stimulating cell-renewal survival, cellular proliferation, evasion of senescence and inhibition of apoptosis. This review suggested CIP2A inhibition as a promising strategy in oncology target therapy.

ceRNA Networks: The Backbone Role in Neoadjuvant Chemoradiotherapy Resistance/Sensitivity of Locally Advanced Rectal Cancer

Approximately 40% of rectal cancers during initial diagnosis are identified as locally advanced rectal cancers (LARCs), for which the standardized treatment scenario is total mesorectal excision following neoadjuvant chemoradiotherapy (nCRT). nCRT can lead to discernible reductions in local relapse rate and distant metastasis rate in LARC patients, in whom previously inoperable tumors may potentially be surgically removed. However, only 4% to 20% cases can attain pathological complete response, and the remaining patients who are unresponsive to nCRT have to suffer from the side effects plus toxicities and may encounter poor survival outcomes due to the late surgical intervention. As such, employing potential biomarkers to differentiate responders from nonresponders before nCRT implementation appears to be the overarching goal. Well-defined competing endogenous RNA (ceRNA) networks include long noncoding RNA (lncRNA)-microRNA (miRNA)-mRNA and circRNA-miRNA-mRNA networks. As ceRNAs, lncRNAs, and circRNAs sponge miRNAs to indirectly suppress miRNAs downstream of oncogenic mRNAs or tumor-suppressive mRNAs. The abnormal expression of mRNAs regulates the nCRT-induced DNA damage repair process through pluralistic carcinogenic signaling pathways, thereby bringing about alterations in the nCRT resistance/sensitivity of tumors. Moreover, many molecular mechanisms relevant to cell proliferation, metastasis, or apoptosis of cancers (eg, epithelial-mesenchymal transition and caspase-9-caspase-3 pathway) are influenced by ceRNA networks. Herein, we reviewed a large group of abnormally expressed mRNAs and noncoding RNAs that are associated with nCRT resistance/sensitivity in LARC patients and ultimately pinpointed the backbone role of ceRNA networks in the molecular mechanisms of nCRT resistance/sensitivity.

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.

2,5-Dimethyl Celecoxib Inhibits Proliferation and Cell Cycle and Induces Apoptosis in Glioblastoma by Suppressing CIP2A/PP2A/Akt Signaling Axis

2,5-Dimethyl-celecoxib (DMC) is a close structural analog of the selective COX-2 inhibitor celecoxib that lacks COX-2-inhibitory function. Thus, DMC is a promising drug for anti-tumor. In this study, we evaluated the efficacy and the molecular basis of DMC in the treatment of human glioblastoma multiforme (GBM). DMC inhibited the growth and proliferation of GBM cell lines (LN229, A172, U251, and U87MG) in a dose-dependent manner (P < 0.001). In GBM cells treated with DMC, detection by flow cytometry showed cell cycle arrest, and proteins involved in cell cycle such as P21 were increased. Compared with control group, Annexin-V/PI-staining in DMC-treatment group was increased, indicating that DMC could induce apoptosis in GBM cells. Also, associated proteins including cleaved caspase 3 and cleaved PARP-1 were increased. It was further explored whether DMC blocked cell cycle and induced apoptosis in GBM cells through CIP2A/PP2A/AKT signaling pathway. After treatment of DMC, the phosphorylation of Akt was reduced while the total Akt level was not affected. DMC suppressed the expression of CIP2A in a time-dependent manner, while the CIP2A overexpression group reversed cell cycle and apoptotic protein expression led by DMC. Finally, in a xenograft model in nude mice using LN229 cells, DMC suppressed tumor growth. These findings proved that DMC could block cell cycle and induce apoptosis in GBM cells by suppressing CIP2A/PP2A/Akt signaling axis, which indicated that DMC could be an effective option for GBM treatment.

CIP2A regulates MYC translation (via its 5'UTR) in colorectal cancer

BACKGROUND

Deregulated expression of MYC is a driver of colorectal carcinogenesis, suggesting that decreasing MYC expression may have significant therapeutic value. CIP2A is an oncogenic factor that regulates MYC expression. CIP2A is overexpressed in colorectal cancer (CRC), and its expression levels are an independent marker for long-term outcome of CRC. Previous studies suggested that CIP2A controls MYC protein expression on a post-transcriptional level.

METHODS

To determine the mechanism by which CIP2A regulates MYC in CRC, we dissected MYC translation and stability dependent on CIP2A in CRC cell lines.

RESULTS

Knockdown of CIP2A reduced MYC protein levels without influencing MYC stability in CRC cell lines. Interfering with proteasomal degradation of MYC by usage of FBXW7-deficient cells or treatment with the proteasome inhibitor MG132 did not rescue the effect of CIP2A depletion on MYC protein levels. Whereas CIP2A knockdown had marginal influence on global protein synthesis, we could demonstrate that, by using different reporter constructs and cells expressing MYC mRNA with or without flanking UTR, CIP2A regulates MYC translation. This interaction is mainly conducted by the MYC 5'UTR.

CONCLUSIONS

Thus, instead of targeting MYC protein stability as reported for other tissue types before, CIP2A specifically regulates MYC mRNA translation in CRC but has only slight effects on global mRNA translation. In conclusion, we propose as novel mechanism that CIP2A regulates MYC on a translational level rather than affecting MYC protein stability in CRC.

Prediction of Response to Neoadjuvant Chemoradiotherapy by MRI-Based Machine Learning Texture Analysis in Rectal Cancer Patients

INTRODUCTION

Neoadjuvant chemoradiotherapy (nCRT) followed by surgical resection is the standard treatment for locally advanced rectal cancer (LARC). Radiomics can be used as noninvasive biomarker for prediction of response to therapy. The main aim of this study was to evaluate the association of MRI texture features of LARC with nCRT response and the effect of Laplacian of Gaussian (LoG) filter and feature selection algorithm in prediction process improvement.

METHODS

All patients underwent MRI with a 3T clinical scanner, 1 week before nCRT. For each patient, intensity, shape, and texture-based features were derived from MRI images with LoG filter using the IBEX software and without preprocessing. We identified responder from a non-responder group using 9 machine learning classifiers. Then, the effect of preprocessing LoG filters with 0.5, 1 and 1.5 value on these classification algorithms' performance was investigated. Eventually, classification algorithm's results were compared in different feature selection methods.

RESULT

Sixty-seven patients with LARC were included in the study. Patients' nCRT responses included 11 patients with Grade 0, 19 with Grade 1, 26 with Grade 2, and 11 with Grade 3 according to AJCC/CAP pathologic grading. In MR Images which were not preprocessed, the best performance was for Ada boost classifier (AUC = 74.8) with T2W MR Images. In T1W MR Images, the best performance was for aba boost classifier (AUC = 78.1) with a σ = 1 preprocessing LoG filter. In T2W MR Images, the best performance was for naive Bayesian network classifier (AUC = 85.1) with a σ = 0.5 preprocessing LoG filter. Also, performance of machine learning models with CfsSubsetEval (CF SUB E) feature selection algorithm was better than others.

CONCLUSION

Machine learning can be used as a response predictor model in LARC patients, but its performance should be improved. A preprocessing LoG filter can improve the machine learning methods performance and at the end, the effect of feature selection algorithm on model's performance is clear.

Cancerous Inhibitor of Protein Phosphatase 2A as a Molecular Marker for Aggressiveness and Survival in Oral Squamous Cell Carcinoma

Cancerous inhibitor of protein phosphatase 2A (CIP2A) has been identified as one of the most commonly altered proteins in human cancers. It blocks the tumor-suppressive action of protein phosphatase 2A (PP2A) complex and enhances malignancy. Thirty-five patients with squamous cell carcinoma of the oral cavity underwent surgical resection of the tumor. CIP2A was assessed by quantitative real-time PCR in the resected tumor tissues and in their adjacent normal tissues. CIP2A was found to be overexpressed in all oral squamous cell carcinoma (OSCC) specimens in comparison to their surrounding normal tissue. CIP2A overexpression was statistically correlated with poor prognostic feature of the tumor. Thus, a high expression level of CIP2A was associated with shorter survival. In conclusion, CIP2A is upregulated in OSCC, and its overexpression is correlated with aggressiveness of the tumor and poor outcome and survival. It may serve as a prognostic marker of OSCC.

Mapping actionable pathways and mutations in brain tumours using targeted RNA next generation sequencing

Many biology-based precision drugs are available that neutralize aberrant molecular pathways in cancer. Molecular heterogeneity and the lack of reliable companion diagnostic biomarkers for many drugs makes targeted treatment of cancer inaccurate for many individuals. Identifying actionable hyperactive biological pathways in individual cancers may improve this situation.

To achieve this we applied a novel targeted RNA next generation sequencing (t/RNA-NGS) technique to surgically obtained glioma tissues. The test combines mutation detection with analysis of biological pathway activities that are involved in tumour behavior in many cancer types (e.g. tyrosine kinase signaling, angiogenesis signaling, immune response, metabolism), via quantitative measurement of transcript levels and splice variants of hundreds of genes. We here present proof of concept that the technique, which uses molecular inversion probes, generates a histology-independent molecular diagnosis and identifies classifiers that are strongly associated with conventional histopathology diagnoses and even with patient prognosis. The test not only confirmed known glioma-associated molecular aberrations but also identified aberrant expression levels of actionable genes and mutations that have so far been considered not to be associated with glioma, opening up the possibility of drug repurposing for individual patients. Its cost-effectiveness makes t/RNA-NGS to an attractive instrument to aid oncologists in therapy decision making.

Euxanthone suppresses tumor growth and metastasis in colorectal cancer via targeting CIP2A/PP2A pathway

AIM

Colorectal cancer (CRC) accounts for over 600,000 deaths annually worldwide. Euxanthone is a flavonoid compound extracted from Polygala caudata, with documented anti-neoplastic actions. The current study aimed to determine the therapeutic potential of euxanthone in CRC.

METHODS AND MATERIALS

Cell Counting Kit-8 (CCK-8) assay was used to analyze the effect of euxanthone on the cell viability, and apoptosis was detected by the TUNEL assay. The in vitro migratory capacity was determined by wound healing and the invasiveness was assessed by Transwell assay. Western blotting was used to determine the level of relevant proteins. Furthermore, a CRC xenograft murine model was used to analyze the therapeutic efficacy of euxanthone in vivo. Isobaric tags for relative and absolute quantification (iTRAQ) was then performed to identify the potential targets of euxanthone. To validate the role of cancerous inhibitor of PP2A (CIP2A) in the anti-cancer effects of euxanthone, plasmid overexpressing CIP2A and shRNA targeting CIP2A were used in in vitro assays.

KEY FINDINGS

Euxanthone decreased cell viability and increased apoptosis in CRC cells, in addition to restraining migration, invasion and EMT. Similarly, euxanthone also effectively suppressed tumor growth and pulmonary metastasis in vivo. iTRAQ analysis identified CIP2A as the primary target responsible for the anticancer effects of euxanthone. The mediatory role of CIP2A was validated when the anticancer activity of euxanthone was significantly blocked by CIP2A overexpression, while CIP2A knockdown sensitized the CRC cells to euxanthone.

SIGNIFICANCE

Euxanthone exerts anti-cancer effects in vitro and in vivo in CRC by targeting CIP2A/PP2A signaling.

ER stress-related ATF6 upregulates CIP2A and contributes to poor prognosis of colon cancer

Endoplasmic reticulum (ER) stress is an adaptive response to various stress conditions and plays emerging roles in cancer. Activating transcription factor 6 (ATF6), one of the three major ER stress transducers, has been shown to contribute to chemoresistance by altering cancer cell survival. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncogene, and its expression has been correlated with the prognosis of patients with cancer. In this study, we aimed to explore the relationship between ER stress‐related ATF signaling and CIP2A. We found that CIP2A expression was positively correlated with ATF6 expression by analyzing publicly available RNA sequence data of patients with colorectal cancer (The Cancer Genome Atlas, TCGA). In addition, we demonstrated that tunicamycin‐induced ER stress in vitro upregulated ATF6 and CIP2A. Mechanistically, we found that ATF6 directly bound to the CIP2A promoter and induced CIP2A gene expression, which contributed to colon cancer cell survival. Furthermore, knockdown of CIP2A reduced the viability of cells under ER stress. Most importantly, immunohistochemical analysis of a tissue microarray from a colon cancer patient cohort showed that higher expression levels of ATF6 and CIP2A were associated with a trend toward poor prognosis. Taken together, our results show that ER stress‐related ATF6 upregulates CIP2A and contributes to the prognosis of colon cancer. Targeting CIP2A may disrupt ER stress‐mediated colon cancer cell survival and thus improve the prognosis of patients with colon cancer.