ECRG2/SPINK7 Tumor Suppressor as Modulator of DNA Damage Response

Esophageal Cancer-Related Gene 2 (ECRG2), also known as Serine Peptidase Inhibitor Kazal type 7 (SPINK7), is a novel tumor suppressor gene from the SPINK family of genes that exhibits anticancer potential. ECRG2 was originally identified during efforts to discover genes involved in esophageal tumorigenesis. ECRG2 was one of those genes whose expression was absent or reduced in primary human esophageal cancers. Additionally, absent or reduced ECRG2 expression was also noted in several other types of human malignancies. ECRG2 missense mutations were identified in various primary human cancers. It was reported that a cancer-derived ECRG2 mutant (valine to glutamic acid at position 30) failed to induce cell death and caspase activation triggered by DNA-damaging anticancer drugs. Furthermore, ECRG2 suppressed cancer cell proliferation in cultured cells and grafted tumors in animals and inhibited cancer cell migration/invasion and metastasis. ECRG2 also was identified as a negative regulator of Hu-antigen R (HuR), an oncogenic RNA-binding protein that is known to regulate mRNA stability and the expression of transcripts corresponding to many cancer-related genes. ECRG2 function is important also for the regulation of inflammatory responses and the maintenance of epithelial barrier integrity in the esophagus. More recently, ECRG2 was discovered as one of the newest members of the pro-apoptotic transcriptional targets of p53. Two p53-binding sites (BS-1 and BS-2) were found within the proximal region of the ECRG2 gene promoter; the treatment of DNA-damaging agents in cancer cells significantly increased p53 binding to the ECRG2 promoter and triggered a strong ECRG2 promoter induction following DNA damage. Further, the genetic depletion of ECRG2 expression significantly impeded apoptotic cell death induced by DNA damage and wild-type p53 in cancer cells. These findings suggest that the loss of ECRG2 expression, commonly observed in human cancers, could play important roles in conferring anticancer drug resistance in human cancers. Thus, ECRG2 is a novel regulator in DNA damage-induced cell death that may also be a potential target for anticancer therapeutics.

Colon cancer transcriptome

Over the last four decades, methodological innovations have continuously changed transcriptome profiling. It is now feasible to sequence and quantify the transcriptional outputs of individual cells or thousands of samples using RNA sequencing (RNA-seq). These transcriptomes serve as a connection between cellular behaviors and their underlying molecular mechanisms, such as mutations. This relationship, in the context of cancer, provides a chance to unravel tumor complexity and heterogeneity and uncover novel biomarkers or treatment options. Since colon cancer is one of the most frequent malignancies, its prognosis and diagnosis seem to be critical. The transcriptome technology is developing for an earlier and more accurate diagnosis of cancer which can provide better protectivity and prognostic utility to medical teams and patients. A transcriptome is a whole set of expressed coding and non-coding RNAs in an individual or cell population. The cancer transcriptome includes RNA-based changes. The combined genome and transcriptome of a patient may provide a comprehensive picture of their cancer, and this information is beginning to affect treatment decision-making in real-time. A full assessment of the transcriptome of colon (colorectal) cancer has been assessed in this review paper based on risk factors such as age, obesity, gender, alcohol use, race, and also different stages of cancer, as well as non-coding RNAs like circRNAs, miRNAs, lncRNAs, and siRNAs. Similarly, they have been examined independently in the transcriptome study of colon cancer.

SPINKs in Tumors: Potential Therapeutic Targets

The serine protease inhibitor Kazal type (SPINK) family includes SPINK1-14 and is the largest branch in the serine protease inhibitor family. SPINKs play an important role in pancreatic physiology and disease, sperm maturation and capacitation, Nager syndrome, inflammation and the skin barrier. Evidence shows that the unregulated expression of SPINK1, 2, 4, 5, 6, 7, and 13 is closely related to human tumors. Different SPINKs exhibit various regulatory modes in different tumors and can be used as tumor prognostic markers. This article reviews the role of SPINK1, 2, 4, 5, 6, 7, and 13 in different human cancer processes and helps to identify new cancer treatment targets.

SPINK7 expression changes accompanied by HER2, P53 and RB1 can be relevant in predicting oral squamous cell carcinoma at a molecular level

The oral squamous cell carcinoma (OSCC), which has a high morbidity rate, affects patients worldwide. Changes in SPINK7 in precancerous lesions could promote oncogenesis. Our aim was to evaluate SPINK7 as a potential molecular biomarker which predicts OSCC stages, compared to: HER2, TP53, RB1, NFKB and CYP4B1. This study used oral biopsies from three patient groups: dysplasia (n = 33), less invasive (n = 28) and highly invasive OSCC (n = 18). The control group consisted of clinically suspicious cases later to be confirmed as normal mucosa (n = 20). Gene levels of SPINK7, P53, RB, NFKB and CYP4B1 were quantified by qPCR. SPINK7 levels were correlated with a cohort of 330 patients from the TCGA. Also, SPINK7, HER2, TP53, and RB1, were evaluated by immunohistofluorescence. One-way Kruskal–Wallis test and Dunn's post-hoc with a p < 0.05 significance was used to analyze data. In OSCC, the SPINK7 expression had down regulated while P53, RB, NFKB and CYP4B1 had up regulated (p < 0.001). SPINK7 had also diminished in TCGA patients (p = 2.10e-6). In less invasive OSCC, SPINK7 and HER2 proteins had decreased while TP53 and RB1 had increased with respect to the other groups (p < 0.05). The changes of SPINK7 accompanied by HER2, P53 and RB1 can be used to classify the molecular stage of OSCC lesions allowing a diagnosis at molecular and histopathological levels.

ECRG2, a novel transcriptional target of p53, modulates cancer cell sensitivity to DNA damage

Esophageal Cancer-Related Gene 2 (ECRG2) is a recently identified tumor suppressor, its regulation and involvement in DNA damage response are unknown. Here, we show that DNA damage-induced ECRG2 upregulation coincided with p53 activation and occurred in a p53-dependent manner. We identified two p53-binding sites within ECRG2 promoter and found the promoter activity, mRNA, and protein expression to be regulated by p53. We show that DNA damage significantly enhanced p53 binding to ECRG2 promoter at the anticipated p53-binding sites. We identified a novel natural ECRG2 promoter variant harboring a small deletion that exists in the genomes of ~38.5% of world population and showed this variant to be defective in responding to p53 and DNA-damage. ECRG2 overexpression induced cancer cell death; ECRG2 gene disruption enhanced cell survival following anticancer drug treatments even when p53 was induced. We showed that lower expression of ECRG2 in multiple human malignancies correlated with reduced disease-free survival in patients. Collectively, our novel findings indicate that ECRG2 is an important target of p53 during DNA damage-induced response and plays a critical role in influencing cancer cell sensitivity to DNA damage-inducing cancer therapeutics.

Chromosome Instability; Implications in Cancer Development, Progression, and Clinical Outcomes

Chromosome instability (CIN) refers to an ongoing rate of chromosomal changes and is a driver of genetic, cell-to-cell heterogeneity. It is an aberrant phenotype that is intimately associated with cancer development and progression. The presence, extent, and level of CIN has tremendous implications for the clinical management and outcomes of those living with cancer. Despite its relevance in cancer, there is still extensive misuse of the term CIN, and this has adversely impacted our ability to identify and characterize the molecular determinants of CIN. Though several decades of genetic research have provided insight into CIN, the molecular determinants remain largely unknown, which severely limits its clinical potential. In this review, we provide a definition of CIN, describe the two main types, and discuss how it differs from aneuploidy. We subsequently detail its impact on cancer development and progression, and describe how it influences metastatic potential with reference to cancer prognosis and outcomes. Finally, we end with a discussion of how CIN induces genetic heterogeneity to influence the use and efficacy of several precision medicine strategies, including patient and risk stratification, as well as its impact on the acquisition of drug resistance and disease recurrence.

The antiprotease SPINK7 serves as an inhibitory checkpoint for esophageal epithelial inflammatory responses

Loss of barrier integrity has an important role in eliciting type 2 immune responses, yet the molecular events that initiate and connect this with allergic inflammation remain unclear. We reveal an endogenous, homeostatic mechanism that controls barrier function and inflammatory responses in esophageal allergic inflammation. We show that a serine protease inhibitor, SPINK7 (serine peptidase inhibitor, kazal type 7), is part of the differentiation program of human esophageal epithelium and that SPINK7 depletion occurs in a human allergic, esophageal condition termed eosinophilic esophagitis. Experimental manipulation strategies reducing SPINK7 in an esophageal epithelial progenitor cell line and primary esophageal epithelial cells were sufficient to induce barrier dysfunction and transcriptional changes characterized by loss of cellular differentiation and altered gene expression known to stimulate allergic responses (for example, FLG and SPINK5). Epithelial silencing of SPINK7 promoted production of proinflammatory cytokines including thymic stromal lymphopoietin (TSLP). Loss of SPINK7 increased the activity of urokinase plasminogen-type activator (uPA), which in turn had the capacity to promote uPA receptor-dependent eosinophil activation. Treatment of epithelial cells with the broad-spectrum antiserine protease, α1 antitrypsin, reversed the pathologic features associated with SPINK7 silencing. The relevance of this pathway in vivo was supported by finding genetic epistasis between variants in TSLP and the uPA-encoding gene, PLAU We propose that the endogenous balance between SPINK7 and its target proteases is a key checkpoint in regulating mucosal differentiation, barrier function, and inflammatory responses and that protein replacement with antiproteases may be therapeutic for select allergic diseases.

Detecting Chromosome Instability in Cancer: Approaches to Resolve Cell-to-Cell Heterogeneity

Chromosome instability (CIN) is defined as an increased rate of chromosome gains and losses that manifests as cell-to-cell karyotypic heterogeneity and drives cancer initiation and evolution. Current research efforts are aimed at identifying the etiological origins of CIN, establishing its roles in cancer pathogenesis, understanding its implications for patient prognosis, and developing novel therapeutics that are capable of exploiting CIN. Thus, the ability to accurately identify and evaluate CIN is critical within both research and clinical settings. Here, we provide an overview of quantitative single cell approaches that evaluate and resolve cell-to-cell heterogeneity and CIN, and discuss considerations when selecting the most appropriate approach to suit both research and clinical contexts.

Proteomic Changes in the Plasma of Broiler Chickens with Femoral Head Necrosis

Femoral head necrosis (FHN) is a skeletal problem in broiler chickens, where the proximal femoral head cartilage shows susceptibility to separation from its growth plate. The selected birds with FHN showed higher body weights and reduced plasma cholesterol. The proteomic differences in the plasma of healthy and FHN-affected chickens were explored using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) and liquid chromatography/electrospray ionization-tandem mass spectrometry (LC-MS/MS) to prospect for protein biomarkers. We isolated two differentially expressed low molecular weight proteins and identified them by MALDI peptide mass fingerprinting as fibrinogen- and fetuin-derived peptides, respectively. These peptides were reduced in birds susceptible to femoral head problems. Quantitation of LC-MS/MS spectra showed elevated levels of gallinacin-9, apolipoprotein A1, and hemoglobin and reduced levels of alpha-1-acid glycoprotein, albumin, and SPINK7 proteins in FHN. These results suggest that the bodyweight and the lipid profiles along with the above proteins can be useful as noninvasive biomarkers of FHN.

Negative regulation of RNA-binding protein HuR by tumor-suppressor ECRG2

Esophageal cancer-related gene 2 (ECRG2) is a newer tumor suppressor whose function in the regulation of cell growth and apoptosis remains to be elucidated. Here we show that ECRG2 expression was upregulated in response to DNA damage, and increased ECRG2 expression induced growth suppression in cancer cells but not in non-cancerous epithelial cells. ECRG2-mediated growth suppression was associated with activation of caspases and marked reduction in the levels of apoptosis inhibitor, X chromosome-linked inhibitor of apoptosis protein (XIAP). ECRG2, via RNA-binding protein human antigen R (HuR), regulated XIAP mRNA stability and expression. Furthermore, ECRG2 increased HuR ubiquitination and degradation but was unable to modulate the non-ubiquitinable mutant form of HuR. We also identified missense and frame-shift ECRG2 mutations in various human malignancies and noted that, unlike wild-type ECRG2, one cancer-derived ECRG2 mutant harboring glutamic acid instead of valine at position 30 (V30E) failed to induce cell death and activation of caspases. This naturally occurring V30E mutant also did not suppress XIAP and HuR. Importantly, the V30E mutant overexpressing cancer cells acquired resistance against multiple anticancer drugs, thus suggesting that ECRG2 mutations appear to have an important role in the acquisition of anticancer drug resistance in a subset of human malignancies.

Expression of bcl-2 and p53 in induction of esophageal cancer cell apoptosis by ECRG2 in combination with cisplatin

AIM

To investigate the mechanisms of induction of apoptosis of esophageal cancer cells by esophageal cancer-related gene 2 (ECRG2) in combination with cisplatin (DDP).

METHODS

Hoechest staining was performed to analyze the effects of single ECRG2 and ECRG2 in combination with DDP on apoptosis of EC9706 cells. The expression levels of p53 and bcl-2 mRNA and protein were determined by RT-PCR and Western blotting, respectively.

RESULTS

The number of apoptotic cells after the treatment with ECRG2 in combination with DDP for 24 hours was more than that after the treatment with single ECRG2. RT-PCR and Western blotting showed that the expression levels of bcl-2 mRNA and protein were both down-regulated, while p53 mRNA and protein were both up-regulated in the cells treated with ECRG2 in combination with DDP compared with those given ECRG2 alone.

CONCLUSION

ECRG2 in combination with DDP can enhance the apoptosis of EC9706 cells, possibly by down-regulating bcl-2 expression and up-regulating p53.

RABL6A, a novel RAB-like protein, controls centrosome amplification and chromosome instability in primary fibroblasts

RABL6A (RAB-like 6 isoform A) is a novel protein that was originally identified based on its association with the Alternative Reading Frame (ARF) tumor suppressor. ARF acts through multiple p53-dependent and p53-independent pathways to prevent cancer. How RABL6A functions, to what extent it depends on ARF and p53 activity, and its importance in normal cell biology are entirely unknown. We examined the biological consequences of RABL6A silencing in primary mouse embryo fibroblasts (MEFs) that express or lack ARF, p53 or both proteins. We found that RABL6A depletion caused centrosome amplification, aneuploidy and multinucleation in MEFs regardless of ARF and p53 status. The centrosome amplification in RABL6A depleted p53−/− MEFs resulted from centrosome reduplication via Cdk2-mediated hyperphosphorylation of nucleophosmin (NPM) at threonine-199. Thus, RABL6A prevents centrosome amplification through an ARF/p53-independent mechanism that restricts NPM-T199 phosphorylation. These findings demonstrate an essential role for RABL6A in centrosome regulation and maintenance of chromosome stability in non-transformed cells, key processes that ensure genomic integrity and prevent tumorigenesis.

Suppression of hepatocarcinoma model in vitro and in vivo by ECRG2 delivery using adenoviral vector

Hepatocarcinoma represents one of the most malignant cancer types. Esophageal cancer-related gene 2 (ECRG2) is found to be critical in the process of carcinogenesis. It regulates urokinase-type plasmin activator receptor and extracellular matrix function and its polymorphism in exon 4 is associated with cancer relapse. To explore new strategies to fight against cancer, here we first systematically evaluated the therapeutic potential as a biological tool using adenoviral vector (Ad-ECRG2). Ad-ECRG2 is exogenously expressed in cytoplasm and is potent to suppress the growth of cancer cell by inducing apoptosis as effective as Ad-p53. Ad-ECRG2 is able to suppress the invasion and adhesion of cancer cells at low titers. It alters the expression of a panel of cancer-related molecules, including nuclear factor-kB, matrix metalloproteinase 2 and E-cadherin, contributing to reverse malignancy phenotype of cancer cells. In vivo experiments show a significant inhibition of cancer growth by intratumoral Ad-ECRG2 administration. No evident toxicity was observed in the model animal during the study. We concluded that ECRG2 is a potential molecular target in biological therapy strategies for cancer treatment.

MicroRNA-1322 regulates ECRG2 allele specifically and acts as a potential biomarker in patients with esophageal squamous cell carcinoma

A short tandem repeat (STR) polymorphism in the 3'UTR region of esophageal cancer-related gene 2 (ECRG2, also known as SPINK7) has been widely reported to be associated with the incidence and the prognosis of esophageal squamous cell carcinoma (ESCC). This study explores how the microRNA binding to the STR region affects ECRG2 expression in ESCC. Dual-luciferase reporter assays were used to verify the effects of the four microRNAs (miR-580, miR-1182, miR-1272, and miR-1322) predicted to bind the STR region of the ECRG2 3' untranslated region (UTR). The expression of identified effective microRNA was then analyzed in 44 paired ESCC and adjacent normal tissues and 402 case-controlled serum samples (divided into a discovery group and an independent validation group) by real-time RT-PCR assay. We found that only miR-1322 could significantly down-regulate the ECRG2 with TCA3 allele (P < 0.01), but it could not down-regulate the ECRG2 with TCA4 allele significantly (P > 0.05). MiR-1322 was also expressed significantly higher in ESCC tissue and serum samples than in controls (both P < 0.01). Additionally, serum levels of miR-1322 yielded an under receiver operating characteristic (ROC) curve area of 0.847 (95% CI, 0.795-0.890) for discriminating ESCCs from healthy controls in the discovery group and a similar result was obtained in the validation group (under ROC area is 0.845; 95%CI, 0.780-0.897). We conclude that miR-1322 can regulate ECRG2 in an allele-specific manner and that serum levels of miR-1322 can serve as a potential diagnostic biomarker for patients with ESCC.

The G1 phase Cdks regulate the centrosome cycle and mediate oncogene-dependent centrosome amplification

Because centrosome amplification generates aneuploidy and since centrosome amplification is ubiquitous in human tumors, a strong case is made for centrosome amplification being a major force in tumor biogenesis. Various evidence showing that oncogenes and altered tumor suppressors lead to centrosome amplification and aneuploidy suggests that oncogenes and altered tumor suppressors are a major source of genomic instability in tumors, and that they generate those abnormal processes to initiate and sustain tumorigenesis. We discuss how altered tumor suppressors and oncogenes utilize the cell cycle regulatory machinery to signal centrosome amplification and aneuploidy.

Mechanisms of chromosomal instability

Most solid tumors are aneuploid, having a chromosome number that is not a multiple of the haploid number, and many frequently mis-segregate whole chromosomes in a phenomenon called chromosomal instability (CIN). CIN positively correlates with poor patient prognosis, indicating that reduced mitotic fidelity contributes to cancer progression by increasing genetic diversity among tumor cells. Here, we review the mechanisms underlying CIN, which include defects in chromosome cohesion, mitotic checkpoint function, centrosome copy number, kinetochore-microtubule attachment dynamics, and cell-cycle regulation. Understanding these mechanisms provides insight into the cellular consequences of CIN and reveals the possibility of exploiting CIN in cancer therapy.

ECRG2 regulates ECM degradation and uPAR/FPRL1 pathway contributing cell invasion/migration

ECRG2 is a novel tumor suppressor gene that shows sequence similarity to KAZAL-type serine protease inhibitor. We have previously demonstrated ECRG2 inhibits migration/invasion of lung cancer PG cells. However, the mechanism by which ECRG2 performs these activities remains unknown. In this study, we found that ECRG2 inhibits proteolysis activity of uPA/plasmin and MMP2, and substantially reduces the ability of HT1080 and HCT-116 cells to invade ECM. Moreover, we demonstrated ECRG2 prevents the cleavage of uPAR, disrupts the association of sD2D3 with FPRL1, and that disruption impairs FPRL1 function. Conversely, depletion of ECRG2 not only markedly increased proteolysis activity of uPA/plasmin and MMP2 but also enhanced the association of uPAR with FPRL1, stimulated cell migration/invasion. Together, our results provide evidence that ECRG2 regulates invasion/migration partly through ECM degradation and uPA/uPAR/FPRL1 pathway, and may represent a novel therapeutic target for cancer.

ECRG2 regulates cell migration/invasion through urokinase-type plasmin activator receptor (uPAR)/beta1 integrin pathway

ECRG2 is a novel gene that shows sequence similarity to KAZAL-type serine protease inhibitor. We have previously demonstrated that ECRG2 inhibits migration/invasion of lung cancer PG cells. However, the mechanism by which ECRG2 performs these activities is a compelling question. Urokinase-type plasmin activator (uPA) binding to uPAR induces migration/invasion through multiple interactors including integrins. In this study, we found that ECRG2 binds specifically to the kringle domain of uPA. Moreover, we demonstrated that ECRG2 forms a complex with uPA.uPAR, that such a complex modifies the dynamical association of uPAR with beta1 integrins, and that disruption inhibits Src/MAP (mitogen-activated protein) kinase pathway, resulting in suppression of cell migration/invasion in an in vitro Matrigel migration/invasion assay. Conversely, depletion of ECRG2 markedly enhanced the association of uPAR with beta1 integrins, elevated basal Src/MAP kinase activation, and stimulated HT1080, MDA-MB-231, and MCF-7 cell migration/invasion. Together, our results provide evidence that ECRG2 is involved in the regulation of migration/invasion through uPA/uPAR/beta1 integrins/Src/MAP kinase pathway and may represent a novel therapeutic target for cancer.