Histone Chaperones and Digestive Cancer: A Review of the Literature

BACKGROUND

The global burden of digestive cancer is expected to increase. Therefore, crucial for the prognosis of patients with these tumors is to identify early diagnostic markers or novel therapeutic targets. There is accumulating evidence connecting histone chaperones to the pathogenesis of digestive cancer. Histone chaperones are now broadly defined as a class of proteins that bind histones and regulate nucleosome assembly. Recent studies have demonstrated that multiple histone chaperones are aberrantly expressed and have distinct roles in digestive cancers.

OBJECTIVE

The purpose of this review is to present the current evidence regarding the role of histone chaperones in digestive cancer, particularly their mechanism in the development and progression of esophageal, gastric, liver, pancreatic, and colorectal cancers. In addition, the prognostic significance of particular histone chaperones in patients with digestive cancer is discussed.

METHODS

According to PRISMA guidelines, we searched the PubMed, Embase, and MEDLINE databases to identify studies on histone chaperones and digestive cancer from inception until June 2022.

RESULTS

A total of 104 studies involving 21 histone chaperones were retrieved.

CONCLUSIONS

This review confirms the roles and mechanisms of selected histone chaperones in digestive cancer and suggests their significance as potential prognostic biomarkers and therapeutic targets. However, due to their non-specificity, more research on histone chaperones should be conducted in the future to elucidate novel strategies of histone chaperones for prognosis and treatment of digestive cancer.

NPM1 promotes cell proliferation by targeting PRDX6 in colorectal cancer

Colorectal cancer is a malignant tumor that begins in the colorectal mucosal epithelium. NPM1 is a nucleolar phosphoprotein that has been linked to tumor progression in humans. NPM1 is significantly overexpressed in a variety of tumors, including colorectal cancer, but its role and mechanism in colorectal cancer remain unknown. Therefore, the purpose of this study was to discover the role of NPM1 in promoting colorectal cancer proliferation via PRDX6 and its molecular mechanism. NPM1 knockdown or overexpression inhibited or promoted the proliferation and cell cycle progression of HCT-116 and HT-29 colorectal cancer cells, respectively, according to our findings. Furthermore, NPM1 knockdown or overexpression increased or decreased intracellular ROS levels. Animal experiments revealed that NPM1 knockdown or overexpression inhibited or promoted the growth of colorectal cancer cells transplanted subcutaneously. NPM1 knockdown or overexpression reduced or increased PRDX6 expression and related enzyme activities, respectively, according to our findings. NPM1 formed a complex with CBX3 as evidenced by immunoprecipitation, and the double luciferase reporter gene assay confirmed that the CBX3-NPM1 complex promoted PRDX6 transcription. Our data support the role of NPM1 in promoting the proliferation of colorectal cancer, which may be accomplished by CBX3 promoting the expression of the antioxidant protein PRDX6 and thus inhibiting intracellular ROS levels. NPM1 and PRDX6 are potential colorectal cancer therapeutic targets.

MYCT1 represses apoptosis of laryngeal cancerous cells through the MAX/miR-181a/NPM1 pathway

MYCT1 is an important gene known to regulate cell viability and apoptosis of laryngeal cancer cells. However, the underlying molecular mechanism remains unclear. Here, we show that MAX enhances the expression of miR-181a by directly binding to its promoter, whereas miR-181a targets NPM1 and suppresses its expression in laryngeal cancer cells. MYCT1 and miR-181a decrease cell viability and colony formation through enhanced apoptosis, whereas NPM1 displays opposite effects in laryngeal cancer cells. Their opposing functions are further supported by the findings (a) that miR-181a is down-regulated, while NPM1 is up-regulated in laryngeal cancer, and (b) that either inhibition of miR-181a or overexpression of NPM1 can revert the pro-apoptotic effects of MYCT1 on laryngeal cancer cells through extracellular and intracellular apoptotic pathways. Our data suggest that MYCT1 may synergistically interact with MAX as a co-transcription factor or a component of MAX transcriptional complex, to transcriptionally regulate the expression of miR-181a, which, in turn, decreases NPM1 expression at post-transcriptional levels, leading to enhanced apoptosis in laryngeal cancer cells. These factors may serve as potential targets for early diagnosis and treatment of laryngeal cancer.

Nucleophosmin/B23 contributes to hepatic insulin resistance through the modulation of NF-κB pathway

Nucleophosmin (NPM)/B23 is an important nucleolar phosphoprotein involved in the regulation of assorted cellular signaling pathways. In the present study, we revealed a critical role of NPM in liver insulin resistance. NPM is markedly upregulated in insulin-resistant liver tissues and palmitic acid (PA)-exposed HepG2 cells both at mRNA and protein levels. Ectopic expression of NPM in hepatocytes aggravated PA-induced insulin resistance, lipid droplet accumulation, glucose intake impairment as well as the expression of gluconeogenic genes. Coinciding with these results, interference of NPM using small interfering RNA (siRNA) oligos ameliorated PA-induced insulin resistance, as revealed by increased phosphorylation of AKT and GSK3β following insulin treatment. As predicted, PA-triggered alterations in glucose intake and the expression of gluconeogenic enzymes were attenuated following NPM depletion. Finally, we showed that NPM plays an indispensible role in PA-induced activation of NF-κB pathway. Both of NF-κB p65 phosphorylation and nuclear translocation were impeded by NPM interference in PA-treated HepG2 cells. Taken together, these findings explicitly demonstrate that NPM participates in the development of liver insulin resistance, suggesting that NPM may serve as a potential therapeutic target of type 2 diabetes.

Knockdown of nucleophosmin 1 suppresses proliferation of triple-negative breast cancer cells through activating CDH1/Skp2/p27kip1 pathway

Background

NPM1 is a multifunctional phosphoprotein that commutes between the cytoplasm and nucleus in cell cycle process, which appears to be actively involved in tumorigenesis. Herein, we sought to investigate the possible role and prognostic value of NPM1 in triple-negative breast cancer (TNBC).

Methods

An array of public databases, including bc-GenExMiner v4.0, GOBO, GEPIA, UAL-CAN, ONCOMINE database and Kaplan-Meier plotter, were used to investigate the expression feature and potential function of NPM1 in TNBC. Immunohistochemistry, immunofluorescence, proliferation and colony formation, flow cytometry and western-blotting assays were used to analyze and verify the function and relevant mechanism of NPM1 in TNBC tissues and cells.

Results

According to analysis from bc-GenExMiner, the expression level of NPM1 was significantly higher in basal-like subtypes than luminal-A, HER-2 or normal-like subtypes of breast cancer (P<0.0001). GOBO database analysis indicated that the expression of NPM1 in basal-A or basal-B was significantly higher than luminal-like breast cancer cells. Immunohistochemistry assay in 52 TNBC tissue samples showed that positive expression of Ki-67 was 93.5% in the high-NPM1-expression group and 66.7% in the low-NPM1-expression group, respectively (P=0.032). Proliferation and colony formation assays demonstrated that inhibition of NPM1 suppressed cell growth by approximately 2-fold and reduced the number of colonies by 3-4-fold in MDA-MB-231 and BT549 cells. Moreover, inhibition of NPM1 in MDA-MB-231 and BT549 cells increased the percentage of cells at G0/G1 phase and decreased the percentage of cells at both S and G2/M phase, as compared with control counterparts. Western-blotting results showed that down-regulation of NPM1 could elevate CDH1 and p27kip1 expression, while decrease Skp2 expression both in MDA-MB-231 and BT549 cells. In addition, high mRNA expression of NPM1 correlated with shorter RFS (HR=1.64, P=0.00013) and OS (HR=2.45, P=0.00034) in patients with TNBC.

Conclusions

NPM1 is significantly high expressed basal-like/triple-negative breast cancer and is correlated with shorter RFS and OS in this subset of patients. Knockdown of NPM1 impairs the proliferative capacity of TNBC cells via activation of the CDH1/Skp2/p27kip1 pathway. Targeting NPM1 is a potential therapeutic strategy against TNBC.

Phosphoproteome Profiling Reveals Multifunctional Protein NPM1 as part of the Irradiation Response of Tumor Cells

To fight resistances to radiotherapy, the understanding of escape mechanisms of tumor cells is crucial. The aim of this study was to identify phosphoproteins that are regulated upon irradiation. The comparative analysis of the phosphoproteome before and after irradiation brought nucleophosmin (NPM1) into focus as a versatile phosphoprotein that has already been associated with tumorigenesis. We could show that knockdown of NPM1 significantly reduces tumor cell survival after irradiation. NPM1 is dephosphorylated stepwise within 1 hour after irradiation at two of its major phosphorylation sites: threonine-199 and threonine-234/237. This dephosphorylation is not the result of a fast cell cycle arrest, and we found a heterogenous intracellular distribution of NPM1 between the nucleoli, the nucleoplasm, and the cytoplasm after irradiation. We hypothesize that the dephosphorylation of NPM1 at threonine-199 and threonine-234/237 is part of the immediate response to irradiation and of importance for tumor cell survival. These findings could make NPM1 an attractive pharmaceutical target to radiosensitize tumor cells and improve the outcome of radiotherapy by inhibiting the pathways that help tumor cells to escape cell death after gamma irradiation.

Poor prognosis of nucleophosmin overexpression in solid tumors: a meta-analysis

BACKGROUND

Nucleophosmin is a non-ribosomal nucleolar phosphoprotein that is found primarily in the nucleolus region of cell nucleus, plays multiple important roles in tumor processes. Accumulated previous studies have reported a potential value of NPM acted as a biomarker for prognosis in various solid tumors, but the results were more inconsistency. We performed this meta-analysis to precisely evaluate the prognostic significance of NPM in solid tumors.

METHODS

Clinical data were collected from a comprehensive literature search in PubMed, Web of Science, Embase, and China National Knowledge Infrastructure databases (up to October, 2017). A total of 11 studied with 997 patients were used to assess the association of NPM expression and patients' overall survival (OS). The hazard ratio (HR) or odds ratio (OR) with its 95% confidence intervals (CI) were calculated to estimate the effect.

RESULTS

The pooled results indicated that higher expression of NPM was observably correlated with poor OS in solid tumor (HR = 1.85, 95% CI: 1.44-2.38, P < 0.001). Furthermore, high expression of NPM was associated with some phenotypes of tumor aggressiveness, such as tumor stage (4 studies, III/IV vs. I/II, OR = 5.21, 95% CI: 2.72-9.56, P < 0.001), differentiation grade (poor vs. well/moderate, OR = 1.82, 95% CI: 1.01-3.27, P = 0.046).

CONCLUSION

This meta-analysis indicated that NPM may act as a valuable prognosis biomarker and a potential therapeutic target in human solid tumors.

Increased nucleophosmin expression is a strong predictor of recurrence and prognosis in patients with N0M0 upper tract urothelial carcinoma undergoing radical nephroureterectomy

PURPOSE

We aimed to evaluate whether increased nucleophosmin expression predicts recurrence and survival in upper tract urothelial carcinoma (UTUC).

METHODS

Specimens from 101 patients with N0M0 UTUC undergoing radical nephroureterectomy were evaluated. Nucleophosmin expression was determined immunohistochemically and categorized into two groups according to nucleophosmin staining intensity. The association between nucleophosmin expression and various clinicopathological factors including Ki-67 expression was analyzed. Multivariate analyses were performed to identify the independent predictors of extraurothelial recurrence and cancer-specific survival.

RESULTS

High nucleophosmin expression was significantly correlated with tumor location, pT ≥3, lymphovascular invasion, lymph node metastasis, and high Ki-67 expression. Patients whose tumors demonstrated high nucleophosmin expression had a significantly higher rate of extraurothelial recurrence and a lower survival rate than those with low nucleophosmin expression. Multivariate analysis showed that pT ≥3, lymph node metastasis, high nucleophosmin expression, and high Ki-67 expression were independent predictors of extraurothelial recurrence. When patients were stratified into three groups according to the number of risk factors, the 2-year extraurothelial recurrence-free survival rates were 92.9% in patients with 0 or 1 risk factor, 76.5% in patients with 2 risk factors, and 9.1% in patients with 3 or 4 risk factors. Regarding cancer-specific survival, lymphovascular invasion and high nucleophosmin expression were independent predictors.

CONCLUSIONS

Increased nucleophosmin expression was a strong predictor of extraurothelial recurrence and cancer-specific survival in patients with N0M0 UTUC undergoing radical nephroureterectomy. Our risk stratification models integrating nucleophosmin expression may provide valuable information on disease recurrence and prognosis.

Lack of prognostic significance of SOCS-1 expression in colorectal adenocarcinomas

INTRODUCTION

Recent studies have indicated that down-regulation of the suppressor of cytokine signaling-1 (SOCS-1) gene results in tumor formation and that SOCS-1 acts as a tumor suppressor gene. SOCS-1 has been also suggested to function as a tumor suppressor with colorectal cancer.

OBJECTIVES

In the present study, we aimed to determine the association of SOCS-1 expression in colorectal cancer tissues with clinicopathologic characteristics immunohistochemically and also to identify its prognostic significance.

MATERIALS AND METHODS

SOCS-1 expression was studied immunohistochemically in 67 patients diagnosed with resected colorectal carcinomas and 30 control subjects.

RESULTS

SOCS-1 expression was found in 46.3% of tumor tissues and 46.7% of the control group. Statistical analyses did not establish any significant association between SOCS-1 expression and clinicopathologic characteristics. Also, no significant association with SOCS-1 expression was found using progression-free survival and overall survival analyses (p=0.326 and p=0.360, respectively).

CONCLUSIONS

Our results show that SOCS-1 has no prognostic significance in colorectal cancer.

High SHIP2 expression indicates poor survival in colorectal cancer

SH2-containing inositol 5′-phosphatase 2 (SHIP2), which generally regulates insulin signaling, cytoskeleton remodeling, and receptor endocytosis, has been suggested to play a significant role in tumor development and progression. However, the associations between SHIP2 expression and the clinical features to evaluate its clinicopathologic significance in colorectal cancer (CRC) have not been determined yet. In the present study, one-step quantitative real-time polymerase chain reaction (qPCR) test and immunohistochemistry (IHC) analysis with CRC tissue microarrays (TMA) were employed to evaluate the mRNA and protein expression of SHIP2 in CRC. The results showed that SHIP2 expression in the mRNA and protein levels was significantly higher in CRC tissues than that in corresponding noncancerous tissues (both P < 0.05). The expression of SHIP2 protein in CRC was related to lymph node metastasis (P = 0.036), distant metastasis (P = 0.001), and overall survival (P = 0.009). Kaplan-Meier method and Cox multifactor analysis suggested that high SHIP2 protein level (P = 0.040) and positive distant metastasis (P = 0.048) were critically associated with the unfavorable survival of CRC patients. The findings suggested that SHIP2 may be identified as a useful prognostic marker in CRC and targeting CRC may provide novel strategy for CRC treatment.