Inhibition of CCN6 (WISP3) expression promotes neoplastic progression and enhances the effects of insulin-like growth factor-1 on breast epithelial cells

Structural insights into regulation of CCN protein activities and functions

CCN proteins play important functions during development, in repair mechanisms following tissue injury, as well as in pathophysiologic mechanisms of metastasis of cancer. CCNs are secreted proteins that have a multimodular structure and are categorized as matricellular proteins. Although the prevailing view is that CCN proteins regulate biologic processes by interacting with a wide array of other proteins in the microenvironment of the extracellular matrix, the molecular mechanisms of action of CCN proteins are still poorly understood. Not dissuading the current view, however, the recent appreciation that these proteins are signaling proteins in their own right and may even be considered preproproteins controlled by endopeptidases to release a C-terminal bioactive peptide has opened new avenues of research. Also, the recent resolution of the crystal structure of two of the domains of CCN3 have provided new knowledge with implications for the entire CCN family. These resolved structures in combination with structural predictions based upon the AlphaFold artificial intelligence tool provide means to shed new light on CCN functions in context of the notable literature in the field. CCN proteins have emerged as important therapeutic targets in several disease conditions, and clinical trials are currently ongoing. Thus, a review that critically discusses structure - function relationship of CCN proteins, in particular as it relates to interactions with other proteins in the extracellular milieu and on the cell surface, as well as to cell signaling activities of these proteins, is very timely. Suggested mechanism for activation and inhibition of signaling by the CCN protein family (graphics generated with BioRender.com ).

WISP3 suppresses ESCC progression by inhibiting the IGF-2-IGF1R-AKT signaling cascade

Esophageal squamous cell carcinoma (ESCC) is a major health problem worldwide, especially in the Chinese population. However, the intrinsic molecular mechanisms of ESCC progression are largely unclear, thus there is an unmet need to identify essential genes governing this disease. Here, we discovered WISP3, an important member of the CCN family, is markedly downregulated in ESCC tissues compared to the normal esophageal epithelium. Downregulation of WISP3 in cancer tissue correlates with worse overall survival of ESCC patients. Using ESCC cell lines as models, we found that forced expression of WISP3 not only suppressed proliferation and migration of cancer cells in vitro, but also inhibited ESCC tumor growth and metastasis in vivo. On the contrary, WISP3 depletion strongly promoted the tumorigenicity of ESCC cells. Mechanistically, we found that WISP3 negates the activity of AKT via inhibiting the IGF-2-IGF1R signaling cascade, which mediates the tumor-suppressive function of WISP3 in esophageal cancers. Together, we identified a novel factor driving the development of ESCC, and revealed a potential therapeutic target for ESCC treatment.

CCN Family Proteins in Cancer: Insight Into Their Structures and Coordination Role in Tumor Microenvironment

The crosstalk between tumor cells and the tumor microenvironment (TME), triggers a variety of critical signaling pathways and promotes the malignant progression of cancer. The success rate of cancer therapy through targeting single molecule of this crosstalk may be extremely low, whereas co-targeting multiple components could be complicated design and likely to have more side effects. The six members of cellular communication network (CCN) family proteins are scaffolding proteins that may govern the TME, and several studies have shown targeted therapy of CCN family proteins may be effective for the treatment of cancer. CCN protein family shares similar structures, and they mutually reinforce and neutralize each other to serve various roles that are tightly regulated in a spatiotemporal manner by the TME. Here, we review the current knowledge on the structures and roles of CCN proteins in different types of cancer. We also analyze CCN mRNA expression, and reasons for its diverse relationship to prognosis in different cancers. In this review, we conclude that the discrepant functions of CCN proteins in different types of cancer are attributed to diverse TME and CCN truncated isoforms, and speculate that targeting CCN proteins to rebalance the TME could be a potent anti-cancer strategy.

A Comparative Genomic and Phylogenetic Analysis of the Origin and Evolution of the CCN Gene Family

CCN gene family members have recently been identified as multifunctional regulators involved in diverse biological functions, especially in vascular and skeletal development. In the present study, a comparative genomic and phylogenetic analysis was performed to show the similarities and differences in structure and function of CCNs from different organisms and to reveal their potential evolutionary relationship. First, CCN homologs of metazoans from different species were identified. Then we made multiple sequence alignments, MEME analysis, and functional sites prediction, which show the highly conserved structural features among CCN metazoans. The phylogenetic tree was further established, and thus CCNs were found undergoing extensive lineage-specific duplication events and lineage-specific expansion during the evolutionary process. Besides, comparative analysis about the genomic organization and chromosomal CCN gene surrounding indicated a clear orthologous relationship among these species counterparts. At last, based on these research results above, a potential evolutionary scenario was generated to overview the origin and evolution of the CCN gene family.

The emerging role of WISP proteins in tumorigenesis and cancer therapy

Accumulated evidence has demonstrated that WNT1 inducible signaling pathway protein (WISP) genes, which belong to members of the CCN growth factor family, play a pivotal role in tumorigenesis and progression of a broad spectrum of human cancers. Mounting studies have identified that WISP proteins (WISP1-3) exert different biological functions in various human malignancies. Emerging evidence indicates that WISP proteins are critically involved in cell proliferation, apoptosis, invasion and metastasis in cancers. Because the understanding of a direct function of WISP proteins in cancer development and progression has begun to emerge, in this review article, we describe the physiological function of WISP proteins in a variety of human cancers. Moreover, we highlight the current understanding of how the WISP protein is involved in tumorigenesis and cancer progression. Furthermore, we discuss that targeting WISP proteins could be a promising strategy for the treatment of human cancers. Hence, the regulation of WISP proteins could improve treatments for cancer patients.

CCN6 regulates IGF2BP2 and HMGA2 signaling in metaplastic carcinomas of the breast

PURPOSE

Metaplastic breast carcinomas are an aggressive subtype of triple-negative breast cancer (TNBC) in which part or all of the adenocarcinoma transforms into a non-glandular component (e.g., spindled, squamous, or heterologous). We discovered that mammary-specific Ccn6/Wisp3 knockout mice develop mammary carcinomas with spindle and squamous differentiation that share upregulation of the oncofetal proteins IGF2BP2 (IMP2) and HMGA2 with human metaplastic carcinomas. Here, we investigated the functional relationship between CCN6, IGF2BP2, and HMGA2 proteins in vitro and in vivo, and their expression in human tissue samples.

METHODS

MMTV-cre;Ccn6^fl/fl tumors and spindle TNBC cell lines were treated with recombinant CCN6 protein or vehicle. IGF2BP2 was downregulated using shRNAs in HME cells with stable CCN6 shRNA knockdown, and subjected to invasion and adhesion assays. Thirty-one human metaplastic carcinomas were arrayed in a tissue microarray (TMA) and immunostained for CCN6, IGF2BP2, and HMGA2.

RESULTS

CCN6 regulates IGF2BP2 and HMGA2 protein expression in MMTV-cre;Ccn6^fl/fl tumors, in MDA-MB-231 and - 468, and in HME cells. CCN6 recombinant protein reduced IGF2BP2 and HMGA2 protein expression, and decreased growth of MMTV-cre;Ccn6^fl/fl tumors in vivo. IGF2BP2 shRNA knockdown was sufficient to reverse the invasive abilities conferred by CCN6 knockdown in HME cells. Analyses of the TCGA Breast Cancer Cohort (n = 1238) showed that IGF2BP2 and HMGA2 are significantly upregulated in metaplastic carcinoma compared to other breast cancer subtypes. In clinical samples, low CCN6 is frequent in tumors with high IGF2BP2/HMGA2 with spindle and squamous differentiation.

CONCLUSIONS

These data shed light into the pathogenesis of metaplastic carcinoma and demonstrate a novel CCN6/IGF2BP2/HMGA2 oncogenic pathway with biomarker and therapeutic implications.

Matricellular CCN6 (WISP3) protein: a tumor suppressor for mammary metaplastic carcinomas

Located at 6q22-23, Ccn6 (WISP3) encodes for a matrix-associated protein of the CCN family, characterized by regulatory, rather than structural, roles in development and cancer. CCN6, the least studied member of the CCN family, shares the conserved multimodular structure of CCN proteins, as well as their tissue and cell-type specific functions. In the breast, CCN6 is a critical regulator of epithelial-to-mesenchymal transitions (EMT) and tumor initiating cells. Studies using human breast cancer tissue samples demonstrated that CCN6 messenger RNA and protein are expressed in normal breast epithelia but reduced or lost in aggressive breast cancer phenotypes, especially inflammatory breast cancer and metaplastic carcinomas. Metaplastic carcinomas are mesenchymal-like triple negative breast carcinomas, enriched for markers of EMT and stemness. RNAseq analyses of the TCGA Breast Cancer cohort show reduced CCN6 expression in approximately 50% of metaplastic carcinomas compared to normal breast. Our group identified frameshift mutations of Ccn6 in a subset of human metaplastic breast carcinoma. Importantly, conditional, mammary epithelial-cell specific ccn6 (wisp3) knockout mice develop invasive high-grade mammary carcinomas that recapitulate human spindle cell metaplastic carcinomas, demonstrating a tumor suppressor function for ccn6. Our studies on CCN6 functions in metaplastic carcinoma highlight the potential of CCN6 as a novel therapeutic approach for this specific type of breast cancer.

IGF-IR signaling in epithelial to mesenchymal transition and targeting IGF-IR therapy: overview and new insights

The insulin-like growth factor-I (IGF-I) signaling induces epithelial to mesenchymal transition (EMT) program and contributes to metastasis and drug resistance in several subtypes of tumors. In preclinical studies, targeting of the insulin-like growth factor-I receptor (IGF-IR) showed promising anti-tumor effects. Unfortunately, high expectations for anti-IGF-IR therapy encountered challenge and disappointment in numerous clinical trials. This review summarizes the regulation of EMT by IGF-I/IGF-IR signaling pathway and drug resistance mechanisms of targeting IGF-IR therapy. Most importantly, we address several factors in the regulation of IGF-I/IGF-IR-associated EMT progression that may be potential predictive biomarkers in targeted therapy.

MMTV-cre;Ccn6 knockout mice develop tumors recapitulating human metaplastic breast carcinomas

Metaplastic breast carcinoma is an aggressive form of invasive breast cancer with histological evidence of epithelial to mesenchymal transition (EMT). However, the defining molecular events are unknown. Here we show that CCN6 (WISP3), a secreted matricellular protein of the CCN (CYR61/CTGF/NOV) family, is significantly down regulated in clinical samples of human spindle cell metaplastic breast carcinoma. We generated a mouse model of mammary epithelial-specific Ccn6 deletion by developing a floxed Ccn6 mouse which was bred with an MMTV-Cre mouse. Ccn6^fl/fl; MMTV-Cre mice displayed severe defects in ductal branching and abnormal age-related involution compared to littermate controls. Ccn6^fl/fl ;MMTV-Cre mice developed invasive high grade mammary carcinomas with bona fide EMT, histologically similar to human metaplastic breast carcinomas. Global gene expression profiling of Ccn6^fl/fl mammary carcinomas and comparison of orthologous genes with a human metaplastic carcinoma signature revealed a significant overlap of 87 genes (p=5×10⁻¹¹). Among the shared deregulated genes between mouse and human are important regulators of epithelial morphogenesis including Cdh1, Ck19, Cldn3 and 4, Ddr1, and Wnt10a. These results document a causal role for Ccn6 deletion in the pathogenesis of metaplastic carcinomas with histological and molecular similarities with human disease. We provide a platform to study new targets in the diagnosis and treatment of human metaplastic carcinomas, and a new disease relevant model in which to test new treatment strategies.

Association and multiple interaction analysis among five XRCC1 polymorphic variants in modulating lung cancer risk in North Indian population

XRCC1 is a scaffold protein that provides for interaction of DNA polymerase, DNA ligase and damaged DNA. Genotyping was done for the five non-synonymous and synonymous variants of XRCC1 i.e. XRCC1, Arg¹⁹⁴Trp, Pro²⁰⁶Pro, Arg²⁸⁰His, Arg³⁹⁹Gln, Gln⁶³²Gln. Logistic regression analysis was used to analyze the association of XRCC1 with lung cancer, followed by data mining analysis which included both Multi-dimensionality reduction (MDR) and Classification and Regression tree (CART) analysis so as to find possible interaction between SNPs on XRCC1 gene. Statistical analysis revealed XRCC1 Gln⁶³²Gln (OR=2.67, p=<0.001) depicted an overall high risk towards lung cancer. Histological subdivision revealed carriers of mutant genotype in case of XRCC1 Arg³⁹⁹Gln imposed a protective effect towards SQCC subtype. Likewise, mutant genotype in XRCC1 Pro²⁰⁶Pro implied a protective effect for SCLC subtype (OR=0.29, p=0.0017) on the contrary XRCC1 Gln⁶³²Gln showed a high risk in SQCC diseased group (OR=4.16, p=<0.0001). Combination of XRCC1 Gln⁶³²Gln with other SNPs revealed XRCC1 Gln⁶³²Gln with Arg¹⁹⁴Trp (OR=2.10, p=0.03) and Pro²⁰⁶Pro (OR=5.6, p<0.0004) increased an overall risk towards lung cancer. Haplotype analysis illustrated haplotype block 11 (CGAGG) carrying minor allele for XRCC1 206 was associated with the highest risk towards lung cancer on the contrary block 4 (CAGAG) carrying mutant allele for XRCC1 399 significantly decreased the risk. Multi-dimensionality reduction (MDR) results showed the three factor model comprising XRCC1 206, 632, 280 as the best model (CVC=10, prediction error=0.34). Further Classification and Regression tree (CART) analysis revealed terminal node 1 carrying mutant of XRCC1 632 and wild type of XRCC1 280 represented the highest risk group. Our results demonstrated high order interaction between SNPs of XRCC1 gene. This study depicted a positive association of XRCC1 Gln⁶³²Gln towards lung cancer, however XRCC1 Arg³⁹⁹Gln, Arg¹⁹⁴Trp showed an overall no effect or protective effect.

Dual roles of CCN proteins in breast cancer progression

The tumor microenvironment has a powerful effect on the development and progression of human breast cancer, which may be used therapeutically. Despite efforts to understand the complex role of the tumor microenvironment in breast cancer development, the specific players and their contributions to tumorigenesis need further investigation. The CCN family of matricellular proteins comprises six members (CCN1-6; CYR61, CTGF, NOV, WISP1-3) with central roles in development, inflammation, and tissue repair. CCN proteins also exert functions during pathological processes including fibrosis and cancer by regulating extracellular signals in the cellular environment. Studies have demonstrated that all six CCN proteins exert functions in breast tumorigenesis. Although CCN proteins share a multimodular structure in which most cysteine residues are conserved within structural motifs, they may have opposing functions in breast cancer progression. A better understanding of the functions of each CCN member will assist in the development of specific therapeutic approaches for breast cancer.

Emerging role of CCN family proteins in tumorigenesis and cancer metastasis (Review)

The CCN family of proteins comprises the members CCN1, CCN2, CCN3, CCN4, CCN5 and CCN6. They share four evolutionarily conserved functional domains, and usually interact with various cytokines to elicit different biological functions including cell proliferation, adhesion, invasion, migration, embryonic development, angiogenesis, wound healing, fibrosis and inflammation through a variety of signalling pathways. In the past two decades, emerging functions for the CCN proteins (CCNs) have been identified in various types of cancer. Perturbed expression of CCNs has been observed in a variety of malignancies. The aberrant expression of certain CCNs is associated with disease progression and poor prognosis. Insight into the detailed mechanisms involved in CCN-mediated regulation may be useful in understanding their roles and functions in tumorigenesis and cancer metastasis. In this review, we briefly introduced the functions of CCNs, especially in cancer.

Role of WISP3 siRNA in proliferation, apoptosis and invasion of bladder cancer cells

Bladder cancer (BC) is the most common cancers of the urinary tract worldwide, killing thousands of people a year. WISP3 is a cysteine-rich protein that belongs to the CCN (Cyr61, CTGF, Nov) family of proteins. Increasing evidences have linked abnormal levels of CCN family members to tumorigenic effects. In the present study, we found that WISP3 was overexpressed in BC. Knockdown of WISP3by RNA interference in two BC cell lines (5367 and SCaBER cells) significantly inhibited cell proliferation, which may be mediated by cell cycle arrest in G1 phase. Moreover, silencing of WISP3 also induced cell apoptosis via increasing the expression of caspase 3 and caspase 9. Depletion of WISP3 notably inhibited the invasion of BC cells. Our data suggests that inhibition of WISP3 may be a therapeutic strategy for BC.

Epithelial Mesenchymal Transition: a double-edged sword

Epithelial mesenchymal transition (EMT) is a physiological process necessary to normal embryologic development. However in genesis of pathological situations, this transition can be perverted and signaling pathways have different regulations from those of normal physiology. In cancer invasion, such a mechanism leads to generation of circulating tumor cells. Epithelial cancer cells become motile mesenchymal cells able to shed from the primary tumor and enter in the blood circulation. This is the major part of the invasive way of cancer. EMT is also implicated in chronic diseases like fibrosis and particularly renal fibrosis. In adult organisms, healing is based on EMT which is beneficial to repair wounds even if it can sometimes exceed its goal and elicit fibrosis. In this review, we delineate the clinical significance of EMT in both physiological and pathological circumstances.

Extracellular matrix in obesity – cancer interactions

Obesity or overweight is a risk factor for several health disorders such as type 2 diabetes, hypertension, and certain cancers. Furthermore, obesity affects almost all body systems including the extracellular matrix (ECM) by generating a pro-inflammatory environment, which are associated with abnormal secretions of several cytokines or hormonal substances, for example, insulin-like growth factors (IGFs), leptin, and sex hormones. These chemical mediators most likely have a great impact on the ECM. Accumulating evidence suggests that both obesity and ECM can influence tumor growth and progression through a number of chemical mediators. Conversely, cells in the connective tissue, namely fibroblasts and macrophages, support and aggravate the inflammatory situation in obesity by releasing several cytokines or growth factors such as vascular endothelial growth factor, epidermal growth factor, and transforming growth factor-beta (TGF-β). A wide range of functions are performed by TGF-β in normal health and pathological conditions including tumorigenesis. Breast cancer in postmenopausal women is a classic example of obesity-related cancer wherein several of these conditions, for example, higher levels of pro-inflammatory cytokines, impairment in the regulation of estrogen and growth factors, and dysregulation of different ECM components may favor the neoplastic process. Aberrant expressions of ECM components such as matrix metalloproteinases or matricellular proteins in both obesity and cancer have been reported by many studies. Nonstructural matricellular proteins, viz., thrombospondins, secreted protein acidic and rich in cysteine (SPARC), and Cyr61-CTGF-Nov (CCN), which function as modulators of cell-ECM interactions, exhibit protean behavior in cancer. Precise understanding of ECM biology can provide potential therapeutic targets to combat obesity-related pathologies.

WISP 1 is an important survival factor in human mesenchymal stromal cells

WNT-induced secreted protein 1 (WISP1/CCN4), a member of the CCN protein family, acts as a downstream factor of the canonical WNT signaling pathway. Its expression is known to affect proliferation and differentiation of human mesenchymal stromal cells (hMSCs), which are fundamental for the development and maintenance of the musculoskeletal system. Whereas a dysregulated, excessive expression of WISP1 often reflects its oncogenic potential via the inhibition of apoptosis, our study emphasizes the importance of WISP1 signaling for the survival of primary human cells. We have established the efficient and specific down-regulation of endogenous WISP1 transcripts by gene silencing in hMSCs and observed cell death as a consequence of WISP1 deficiency. This was confirmed by Annexin V staining for apoptotic cells. DNA microarray analyses of WISP1 down-regulated versus control samples revealed several clusters of differentially expressed genes important for apoptosis induction such as TNF-related apoptosis-inducing ligand 1 (TRAIL) and the corresponding apoptosis-inducing receptors TRAIL-R1 and -R2. An increased expression of TRAIL and its receptors TRAIL-R1 and -R2 in WISP1-deficient hMSCs was confirmed by immunocytofluorescence. Accordingly, WISP1 deficiency is likely to cause TRAIL-induced apoptosis. This is an important novel finding, which suggests that WISP1 is indispensable for the protection of healthy hMSCs against TRAIL-induced apoptosis.

The role of the CCN family of proteins in female reproduction

The CCN family of proteins consists of six high homologous matricellular proteins which act predominantly by binding to heparin sulphate proteoglycan and a variety of integrins. Interestingly, CCN proteins are regulated by ovarian steroid hormones and are able to adapt to changes in oxygen concentration, which is a necessary condition for successful implantation. CCN1 is involved in processes of angiogenesis within reproductive systems, thereby potentially contributing to diseases such as endometriosis and disturbed angiogenesis in the placenta and fetus. In the ovary, CCN2 is the key factor for follicular development, ovulation and corpora luteal luteolysis, and its deletion leads to fertility defects. CCN1, CCN2 and CCN3 seem to be regulators for human trophoblast proliferation and migration, but with CCN2 acting as a counterweight. Alterations in the expression of these three proteins could contribute to the shallow invasion properties observed in preeclampsia. Little is known about the role of CCN4-6 in the reproductive organs. The ability of CCN1, CCN2 and CCN3 to interact with numerous receptors enables them to adapt their biological function rapidly to the continuous remodelling of the reproductive organs and in the development of the placenta. The CCN proteins mediate their specific cell physiological function through the receptor type of their binding partner followed by a defined signalling cascade. Because of their partly overlapping expression patterns, they could act in a concert synergistically or in an opposite way within the reproductive organs. Imbalances in their expression levels are correlated to different human reproductive diseases, such as endometriosis and preeclampsia.

CCN6 knockdown disrupts acinar organization of breast cells in three-dimensional cultures through up-regulation of type III TGF-β receptor

While normal cells in the human breast are organized into acinar structures, disruption of the acinar architecture is a hallmark of cancer. In a three-dimensional model of morphogenesis, we show that down-regulation of the matrix-associated tumor suppressor protein CCN6 (WNT1-inducible-signaling pathway protein 3) disrupts breast epithelial cell polarity and organization into acini through up-regulation of the type III transforming growth factor-β receptor (TβRIII or betaglycan). Down-regulation of CCN6 in benign breast cells led to loss of tissue polarity and resulted in cellular disorganization with loss of α6 integrin-rich basement membrane and the basolateral polarity protein E-cadherin. Silencing of TβRIII with shRNA and siRNA rescued the ability of breast epithelial cells to form polarized acinar structures with reduced matrix invasion and restored the correct expression of α6 integrin and E-cadherin. Conversely, CCN6 overexpression in aggressive breast cancer cells reduced TβRIII in vitro and in a xenograft model of CCN6 overexpression. The relevance of our studies to human breast cancer is highlighted by the finding that CCN6 protein levels are inversely associated with TβRIII protein in 64%of invasive breast carcinomas. These results reveal a novel function of the matricellular protein CCN6 and establish a mechanistic link between CCN6 and TβRIII in maintaining acinar organization in the breast.

Tissue-based identification of stem cells and epithelial-to-mesenchymal transition in breast cancer

Pathologists have recognized breast cancer heterogeneity for decades, but its causes were unknown. In recent years, basic science and translational studies have demonstrated that cancer stem cells contribute to the heterogeneous histologic and functional characteristics of breast cancer. Even more recently, the ability of breast epithelial cells to undergo an epithelial-to-mesenchymal transition has been linked to the acquisition of stem cells properties and enhanced tumor invasion, metastasis, and resistance to available treatments. The stem cells and cells undergoing epithelial-to-mesenchymal transition are attractive targets for therapy and breast cancer prevention. Despite current challenges, their identification in breast tissue samples would enable pathologists to discover and validate prognostic and predictive markers as well as identify markers of increased risk for breast cancer.

Molecular alterations in metaplastic breast carcinoma

Metaplastic carcinoma of the breast is a rare and heterogeneous subtype of breast carcinoma with a generally poor outcome, and few therapeutic options once disease recurs or progresses. Metaplastic carcinomas of the breast are usually of a larger size at diagnosis, with less frequent nodal metastasis compared with invasive ductal carcinoma no special type, and lack hormone and HER2 receptor expression. Recent research has revealed some potentially actionable genetic changes in a subset of these rare tumours. However, ongoing efforts to further characterise the genetic basis and the molecular alterations underlying the distinctive morphological and clinical characteristics of these tumours are needed in order to identify new targets for treatment. This review will describe the theories of pathogenesis of metaplastic breast carcinoma, and highlight genetic changes and potential therapeutic targets in this generally poor prognosis malignancy.

A comparison of epithelial-to-mesenchymal transition and re-epithelialization

Wound healing and cancer metastasis share a common starting point, namely, a change in the phenotype of some cells from stationary to motile. The term, epithelial-to-mesenchymal transition (EMT) describes the changes in molecular biology and cellular physiology that allow a cell to transition from a sedentary cell to a motile cell, a process that is relevant not only for cancer and regeneration, but also for normal development of multicellular organisms. The present review compares the similarities and differences in cellular response at the molecular level as tumor cells enter EMT or as keratinocytes begin the process of re-epithelialization of a wound. Looking toward clinical interventions that might modulate these processes, the mechanisms and outcomes of current and potential therapies are reviewed for both anti-cancer and pro-wound healing treatments related to the pathways that are central to EMT. Taken together, the comparison of re-epithelialization and tumor EMT serves as a starting point for the development of therapies that can selectively modulate different forms of EMT.

Matricellular proteins: a sticky affair with cancers

The multistep process of metastasis is a major hallmark of cancer progression involving the cointeraction and coevolution of the tumor and its microenvironment. In the tumor microenvironment, tumor cells and the surrounding stromal cells aberrantly secrete matricellular proteins, which are a family of nonstructural proteins in the extracellular matrix (ECM) that exert regulatory roles via a variety of molecular mechanisms. Matricellular proteins provide signals that support tumorigenic activities characteristic of the metastastic cascade such as epithelial-to-mesenchymal (EMT) transition, angiogenesis, tumor cell motility, proliferation, invasion, evasion from immune surveillance, and survival of anoikis. Herein, we review the current understanding of the following matricellular proteins and highlight their pivotal and multifacted roles in metastatic progression: angiopoietin-like protein 4 (ANGPTL4), CCN family members cysteine-rich angiogenic inducer 61 (Cyr61/CCN1) and CCN6, osteopontin (OPN), secreted protein acidic and rich in cysteine (SPARC), tenascin C (TNC), and thrombospondin-1 and -2 (TSP1, TSP2). Insights into the signaling mechanisms resulting from the interaction of these matricellular proteins and their respective molecular partner(s), as well as their subsequent contribution to tumor metastasis, are discussed. In addition, emerging evidences of their promising potential as therapeutic options and/or targets in the treatment of cancer are also highlighted.

On how CCN6 suppresses breast cancer growth and invasion

Living cells communicate with their microenvironment and exchange information through signaling pathways in order to carry out most biological processes. The CCN family of proteins has the ability to coordinate the extracellular and intracellular signaling pathways and epithelial-stromal cross-talks. CCN proteins have been shown to play roles in multiple processes including cancer, either as tumor suppressors or oncogenes. Particularly, loss of CCN6 expression has been reported in highly aggressive breast cancer types, especially in inflammatory breast cancer and breast cancer with axillary lymph node metastasis. Recent findings can better explain the biological relevance of CCN6 as a tumor suppressor protein in breast tumorigenesis. CCN6 loss triggers the process of epithelial to mesenchymal transition (EMT), which converts epithelial cells into migratory and invasive mesenchymal-like cells at least in part through modulation of IGF-1 receptor signaling pathway. Emerging data support the hypothesis that CCN6 also exerts growth factor independent functions, especially related to cell survival and anoikis resistance. Thus, our work provides new insights into the functions and mechanisms of tumor suppression exerted by CCN6 in the breast.

CCN6 (WISP3) decreases ZEB1-mediated EMT and invasion by attenuation of IGF-1 receptor signaling in breast cancer

During progression of breast cancer, CCN6 protein exerts tumor inhibitory functions. CCN6 is a secreted protein that modulates the insulin-like growth factor-1 (IGF-1) signaling pathway. Knockdown of CCN6 in benign mammary epithelial cells triggers an epithelial to mesenchymal transition (EMT), with upregulation of the transcription factor ZEB1/δEF1. How CCN6 regulates ZEB1 expression is unknown. We hypothesized that CCN6 might regulate ZEB1, EMT and breast cancer invasion by modulating IGF-1 signaling. Exogenously added human recombinant CCN6 protein was sufficient to downregulate ZEB1 mRNA and protein levels in CCN6-deficient (CCN6 KD) HME cells and MDA-MB-231 breast cancer cells. Recombinant CCN6 protein decreased invasion of CCN6 KD cells compared with controls. We discovered that knockdown of CCN6 induced IGF-1 secretion in HME cells cultivated in serum-free medium to higher concentrations than found in MDA-MB-231 cells. Treatment with recombinant CCN6 protein was sufficient to decrease IGF-1 protein and mRNA to control levels, rescuing the effect of CCN6 knockdown. Specific inhibition of IGF-1 receptors using the pharmacological inhibitor NVP-AE541 or short hairpin shRNAs revealed that ZEB1 upregulation due to knockdown of CCN6 requires activation of IGF-1 receptor signaling. Recombinant CCN6 blunted IGF-1-induced ZEB1 upregulation in MDA-MB-231 cells. Our data define a pathway in which CCN6 attenuates IGF-1 signaling to decrease ZEB1 expression and invasion in breast cancer. These results suggest that CCN6 could be a target to prevent or halt breast cancer invasion.

High-resolution comparative genomic hybridization of inflammatory breast cancer and identification of candidate genes

BACKGROUND

Inflammatory breast cancer (IBC) is an aggressive form of BC poorly defined at the molecular level. We compared the molecular portraits of 63 IBC and 134 non-IBC (nIBC) clinical samples.

METHODOLOGY/FINDINGS

Genomic imbalances of 49 IBCs and 124 nIBCs were determined using high-resolution array-comparative genomic hybridization, and mRNA expression profiles of 197 samples using whole-genome microarrays. Genomic profiles of IBCs were as heterogeneous as those of nIBCs, and globally relatively close. However, IBCs showed more frequent "complex" patterns and a higher percentage of genes with CNAs per sample. The number of altered regions was similar in both types, although some regions were altered more frequently and/or with higher amplitude in IBCs. Many genes were similarly altered in both types; however, more genes displayed recurrent amplifications in IBCs. The percentage of genes whose mRNA expression correlated with CNAs was similar in both types for the gained genes, but ∼7-fold lower in IBCs for the lost genes. Integrated analysis identified 24 potential candidate IBC-specific genes. Their combined expression accurately distinguished IBCs and nIBCS in an independent validation set, and retained an independent prognostic value in a series of 1,781 nIBCs, reinforcing the hypothesis for a link with IBC aggressiveness. Consistent with the hyperproliferative and invasive phenotype of IBC these genes are notably involved in protein translation, cell cycle, RNA processing and transcription, metabolism, and cell migration.

CONCLUSIONS

Our results suggest a higher genomic instability of IBC. We established the first repertory of DNA copy number alterations in this tumor, and provided a list of genes that may contribute to its aggressiveness and represent novel therapeutic targets.

A homozygous recurring mutation in WISP3 causing progressive pseudorheumatoid arthropathy

WISP3 is a member of the CCN (for CTGF, CYR61, and NOV) gene family, which encodes cysteine-rich secreted proteins with roles in cell growth and differentiation. Mutations in the WISP3 gene are associated with the autosomal recessive skeletal disorder, also known as progressive pseudorheumatoid arthropathy of childhood (PPAC). We diagnosed three siblings from a non-consanguineous family with PPAC. The patients were asymptomatic in early childhood. Signs and symptoms of disease that include progressive joint stiffness, swelling of the finger joints, and osteopenia, and slow linear growth developed between 2 and 8 years of age. PCR amplification and direct sequencing of the WISP3 gene revealed a homozygous mutation at nucleotide 156 of the WISP3 gene, resulting in a Cys52-to-ter substitution. This mutation has previously been reported in French, Italian, and Arab families. Interestingly, the C52X mutation was found to be associated with a c.248G-->A (G83E) variation, suggesting the existence of a founder effect. By contrast, the presence of the same aberration in three different ethnic groups could imply that this particular site is prone to mutation. Basal fasting concentrations of growth hormone, insulin-like growth factor-1, and insulin-like growth factor binding protein-3, as well as glucose and insulin levels revealed no aberrations. In conclusion, consideration of this rare disease that causes significant morbidity with short stature, osteopenia and arthritic complaints would prevent unnecessary examinations and treatment attempts. Testing for this specific mutation in suspected cases could provide a rapid and definitive diagnosis.

Blockade of CCN6 (WISP3) activates growth factor-independent survival and resistance to anoikis in human mammary epithelial cells

CCN6 is a secreted cysteine-rich matricellular protein (36.9 kDa) that exerts growth-inhibitory functions in breast cancer. Reduction or loss of CCN6 protein has been reported in invasive carcinomas of the breast with lymph node metastasis and in inflammatory breast cancer. However, the mechanism by which CCN6 loss promotes breast cancer growth remains to be defined. In the present study, we developed lentiviral-mediated short hairpin RNA CCN6 knockdown (KD) in nontumorigenic mammary epithelial cells MCF10A and HME. We discovered that CCN6 KD protects mammary epithelial cells from apoptosis and activates growth factor-independent survival. In the absence of exogenous growth factors, CCN6 KD was able to promote growth under anchorage-independent conditions and triggered resistance to detachment-induced cell death (anoikis). On serum starvation, CCN6 KD was sufficient for activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Growth factor-independent cell survival was stunted in CCN6 KD cells when treated with either human recombinant CCN6 protein or the PI3K inhibitor LY294002. Targeted inhibition of Akt isoforms revealed that the survival advantage rendered by CCN6 KD requires specific activation of Akt-1. The relevance of our studies to human breast cancer is highlighted by the finding that low CCN6 protein levels are associated with upregulated expression of phospho-Akt-1 (Ser(473)) in 21% of invasive breast carcinomas. These results enable us to pinpoint one mechanism by which CCN6 controls survival of breast cells mediated by the PI3K/Akt-1 pathway.

Human embryonic stem cell-derived mesoderm-like epithelium transitions to mesenchymal progenitor cells

Human embryonic stem cells (hESC) have the potential to produce all of the cells in the body. They are able to self-renew indefinitely, potentially making them a source for large-scale production of therapeutic cell lines. Here, we developed a monolayer differentiation culture that induces hESC (WA09 and BG01) to form epithelial sheets with mesodermal gene expression patterns (BMP4, RUNX1, and GATA4). These E-cadherin+ CD90low cells then undergo apparent epithelial-mesenchymal transition for the derivation of mesenchymal progenitor cells (hESC-derived mesenchymal cells [hES-MC]) that by flow cytometry are negative for hematopoietic (CD34, CD45, and CD133) and endothelial (CD31 and CD146) markers, but positive for markers associated with mesenchymal stem cells (CD73, CD90, CD105, and CD166). To determine their functionality, we tested their capacity to produce the three lineages associated with mesenchymal stem cells and found they could form osteogenic and chondrogenic, but not adipogenic lineages. The derived hES-MC were able to remodel and contract collagen I lattice constructs to an equivalent degree as keloid fibroblasts and were induced to express alpha-smooth muscle actin when exposed to transforming growth factor (TGF)-beta1, but not platelet derived growth factor-B (PDGF-B). These data suggest that the derived hES-MC are multipotent cells with potential uses in tissue engineering and regenerative medicine and for providing a highly reproducible cell source for adult-like progenitor cells.

The emerging role of CCN6 in breast cancer invasion

The CCN family of matricellular proteins is essential for cell communication and mediation of epithelial stromal cross-talks with roles in development and cancer. In particular, loss of CCN6 messenger RNA expression has been recognized in highly aggressive breast cancers, especially in inflammatory breast cancer and breast cancers with axillary lymph node metastasis. Recent findings can better explain the relevance of CCN6's reduced expression on human invasive breast carcinomas. CCN6 has been shown to play a role in the process of epithelial to mesenchymal transition (EMT), which converts epithelial cells into migratory mesenchymal-like cells with invasive abilities. Although the mechanism by which CCN6 promotes EMT and invasion has not been fully elucidated, current data suggest that it involves the recruitment of the transcriptional regulators Snai1 and ZEB1 to the E-cadherin promoter.

E-cadherin, beta-catenin, and ZEB1 in malignant progression of cancer

The embryonic program 'epithelial-mesenchymal transition' (EMT) is activated during tumor invasion in disseminating cancer cells. Characteristic to these cells is a loss of E-cadherin expression, which can be mediated by EMT-inducing transcriptional repressors, e.g. ZEB1. Consequences of a loss of E-cadherin are an impairment of cell-cell adhesion, which allows detachment of cells, and nuclear localization of beta-catenin. In addition to an accumulation of cancer stem cells, nuclear beta-catenin induces a gene expression pattern favoring tumor invasion, and mounting evidence indicates multiple reciprocal interactions of E-cadherin and beta-catenin with EMT-inducing transcriptional repressors to stabilize an invasive mesenchymal phenotype of epithelial tumor cells.

Proteins on the catwalk: modelling the structural domains of the CCN family of proteins

The CCN family of proteins (CCN1, CCN2, CCN3, CCN4, CCN5 and CCN6) are multifunctional mosaic proteins that play keys roles in crucial areas of physiology such as angiogenesis, skeletal development tumourigenesis, cell proliferation, adhesion and survival. This expansive repertoire of functions comes through a modular structure of 4 discrete domains that act both independently and in concert. How these interactions with ligands and with neighbouring domains lead to the biological effects is still to be explored but the molecular structure of the domains is likely to play an important role in this. In this review we have highlighted some of the key features of the individual domains of CCN family of proteins based on their biological effects using a homology modelling approach.

Expression of CCN family of genes in human skin in vivo and alterations by solar-simulated ultraviolet irradiation

The CCN family of proteins is involved in diverse biological functions such as cell growth, adhesion, migration, angiogenesis, and regulation of extracellular matrix. We have investigated expression of CCN family genes and alternations induced by solar-simulated ultraviolet irradiation in human skin in vivo. Transcripts of all six CCN genes were expressed in human skin in vivo. CCN5 was most abundantly expressed followed by CCN2>CCN3>CCN1>CCN4>CCN6. Solar-simulated ultraviolet irradiation increased mRNA expression of CCN1 and CCN2. In contrast, mRNA levels of CCN3, CCN4, CCN5, and CCN6, were reduced. Knowledge gained from this study provides the foundation to explore the functional roles of CCN gene products in cutaneous biology and responses to solar ultraviolet irradiation.

The epithelial-to-mesenchymal transition and cancer stem cells: a coalition against cancer therapies

During cancer progression, some cells within the primary tumor may reactivate a latent embryonic program known as epithelial-to-mesenchymal transition (EMT). Through EMT, transformed epithelial cells can acquire the mesenchymal traits that seem to facilitate metastasis. Indeed, there is accumulating evidence that EMT and mesenchymal-related gene expression are associated with aggressive breast cancer subtypes and poor clinical outcome in breast cancer patients. More recently, the EMT program was shown to endow normal and transformed mammary epithelial cells with stem cell properties, including the ability to self-renew and efficiently initiate tumors. This link between EMT and stem cells may have numerous implications in the progression of breast tumors. The EMT process may facilitate the generation of cancer cells with the mesenchymal traits needed for dissemination as well as the self-renewal properties needed for initiation of secondary tumors. Breast cancer stem cells are resistant to many conventional cancer therapies, which can promote tumor relapse. Therefore, the generation of cancer stem cells by EMT may promote the development of refractory and resistant breast tumors. The purpose of this review is to summarize the findings related to EMT and stem cells in cancer progression and therapy resistance.

The CCN family of proteins: structure-function relationships

The CCN proteins are key signalling and regulatory molecules involved in many vital biological functions, including cell proliferation, angiogenesis, tumourigenesis and wound healing. How these proteins influence such a range of functions remains incompletely understood but is probably related to their discrete modular nature and a complex array of intra- and inter-molecular interactions with a variety of regulatory proteins and ligands. Although certain aspects of their biology can be attributed to the four individual modules that constitute the CCN proteins, recent results suggest that some of their biological functions require cooperation between modules. Indeed, the modular structure of CCN proteins provides important insight into their structure-function relationships.

The CCN family of proteins: structure-function relationships

The CCN proteins are key signalling and regulatory molecules involved in many vital biological functions, including cell proliferation, angiogenesis, tumourigenesis and wound healing. How these proteins influence such a range of functions remains incompletely understood but is probably related to their discrete modular nature and a complex array of intra- and inter-molecular interactions with a variety of regulatory proteins and ligands. Although certain aspects of their biology can be attributed to the four individual modules that constitute the CCN proteins, recent results suggest that some of their biological functions require cooperation between modules. Indeed, the modular structure of CCN proteins provides important insight into their structure-function relationships.

Detection of copy number alterations in metastatic melanoma by a DNA fluorescence in situ hybridization probe panel and array comparative genomic hybridization: a southwest oncology group study (S9431)

PURPOSE

Gene copy number alteration (CNA) is common in malignant melanoma and is associated with tumor development and progression. The concordance between molecular cytogenetic techniques used to determine CNA has not been evaluated on a large set of loci in malignant melanoma.

EXPERIMENTAL DESIGN

A panel of 16 locus-specific fluorescence in situ hybridization (FISH) probes located on eight chromosomes was used to identify CNA in touch preparations of frozen tissue samples from 19 patients with metastatic melanoma (SWOG-9431). A subset (n = 11) was analyzed using bacterial artificial chromosome (BAC) array comparative genomic hybridization (aCGH) of DNA isolated directly from touch-preparation slides.

RESULTS

By FISH, most samples showed loss near or at WISP3/6p21, CCND3/6q22, and CDKN2A/9p21 (>75% of samples tested). More than one third of CDKN2A/9p21 losses were biallelic. Gains of NEDD9/6p24, MET/7q31, and MYC/8q24 were common (57%, 47%, and 41%, respectively) and CNA events involving 9p21/7p12.3 and MET were frequently coincident, suggesting gain of the whole chromosome 7. Changes were confirmed by aCGH, which also uncovered many discreet regions of change, larger than a single BAC. Overlapping segments observed in >45% of samples included many of the loci analyzed in the FISH study, in addition to other WNT pathway members, and genes associated with TP53 pathways and DNA damage response, repair, and stability.

CONCLUSIONS

This study outlines a set of CNAs at the gene and regional level, using FISH and aCGH, which may provide a benchmark for future studies and may be important in selection of individual therapy for patients with metastatic malignant melanoma.

Genetic changes of Wnt pathway genes are common events in metaplastic carcinomas of the breast

PURPOSE

Metaplastic carcinomas are distinct invasive breast carcinomas with aberrant nonglandular differentiation, which may be spindle, squamous, or chondroid. The limited effective treatments result from the lack of knowledge of its molecular etiology. Given the role of the Wnt pathway in cell fate and in the development of breast cancer, we hypothesized that defects in this pathway may contribute to the development of metaplastic carcinomas.

DESIGN

In 36 primary metaplastic carcinomas, we comprehensively determined the prevalence of and mechanism underlying beta-catenin and Wnt pathway deregulation using immunohistochemistry for beta-catenin expression and localization and mutational analysis for CTNNB1 (encoding beta-catenin), APC, WISP3, AXIN1, and AXIN2 genes. By immunohistochemistry, normal beta-catenin was seen as membrane staining, and it was aberrant when >5% of tumor cells had nuclear or cytoplasmic accumulation or reduced membrane staining.

RESULTS

By immunohistochemistry, aberrant beta-catenin was present in 33 of 36 (92%) cases, revealing deregulation of the Wnt pathway. CTNNB1 missense mutations were detected in 7 of 27 (25.9%) tumors available for mutation analyses. All mutations affected the NH(2)-terminal domain of beta-catenin, presumably rendering the mutant protein resistant to degradation. Two of 27 (7.4%) tumors had mutations of APC, and 5 (18.5%) carried a frame shift mutation of WISP3. No AXIN1 or AXIN2 mutations were found.

CONCLUSIONS

Activation of the Wnt signaling pathway is common in this specific subtype of breast carcinoma. The discovery of CTNNB1, APC, and WISP3 mutations may result in new treatments for patients with metaplastic carcinomas of the breast.

Mesenchymal transition in kidney collecting duct epithelial cells

Progressive organ damage due to tissue scarring and fibrosis is a paradigm shared by numerous human diseases including chronic kidney disease. The purpose of this study was to confirm the hypothesis that collecting duct (CD) epithelial cells can undergo mesenchymal transition (EMT) in vitro. The mechanism by which CDs undergo EMT is complex and involves both early and late cellular events. Early events include rapid insulin-like growth factor (IGF)-induced Akt and GSK-3beta phosphorylation, associated with early disruption of E-cadherin-beta-catenin membrane colocalization, with translocation of E-cadherin to endosomes, with translocation of beta-catenin to the nucleus, and with an increase in Snail expression. Transforming growth factor-beta1, on the other hand, induced early activation of Smad3 and its translocation to the nucleus, Erk1/2 phosphorylation, and early disruption of membrane E-cadherin localization. The late consequences of these events included a phenotypic transformation of the cells to a mesenchymal morphology with associated increase in vimentin and alpha-smooth muscle actin protein expression and a decrease in total cellular E-cadherin expression, detectable as early as 24 h after stimulation.

Inhibition of CCN6 (Wnt-1-induced signaling protein 3) down-regulates E-cadherin in the breast epithelium through induction of snail and ZEB1

The cysteine-rich protein CCN6 [or Wnt-1-induced signaling protein 3 (WISP3)] exerts tumor-suppressive effects in aggressive inflammatory breast cancer. Loss of CCN6 is associated with poorly differentiated phenotypes and increased invasion. Here, we show that reduction of CCN6 expression occurs in 60% of invasive breast carcinomas and is associated with axillary lymph node metastases. Furthermore, low CCN6 expression in invasive carcinoma tissue samples correlates with reduced expression of E-cadherin. In vitro, RNA interference knockdown of CCN6 in two benign human mammary epithelial cell lines (HME and MCF10A) decreased expression of E-cadherin protein and mRNA and reduced activity of the E-cadherin promoter; this reduction was dependent on intact E-box elements. CCN6 knockdown in HME cells resulted in up-regulation of the E-cadherin transcriptional repressors Snail and ZEB1 and enhanced their recruitment and binding to the E-cadherin promoter as analyzed by chromatin immunoprecipitation assays. Small interfering RNA-mediated knockdown of ZEB1 or Snail blocked the down-regulation of E-cadherin caused by CCN6 inhibition. These data show, for the first time, that CCN6 expression is reduced or lost in a substantial number of invasive breast carcinomas and that CCN6 modulates transcriptional repressors of E-cadherin. Together, our results lead to a new hypothesis that Snail and ZEB1 are downstream of CCN6 and play a critical role in CCN6-mediated regulation of E-cadherin in breast cancer.

Genetic Determinants of Aggressive Breast Cancer

The development and spread of breast and other human cancers are caused by the overexpression, mutation, and/or deletion of specific genes that drive these events. Finding genetic and molecular differences between cancerous and healthy cells can reveal the genetic determinants of cancer. This knowledge results in a better understanding of the carcinogenic process and improved predictive power, with implications for identifying new drug targets, designing novel therapies, and improving preclinical and clinical studies. We review the concepts of biomarker, genetic marker, and genetic determinant in cancer, with particular focus on the most aggressive and lethal form of breast cancer, termed inflammatory breast cancer (IBC). Using IBC as an example, we describe in detail the approaches to identify the genes that are responsible for-and not merely associated with-this disease.

The CCN family member Wisp3, mutant in progressive pseudorheumatoid dysplasia, modulates BMP and Wnt signaling

In humans, loss-of-function mutations in the gene encoding Wnt1 inducible signaling pathway protein 3 (WISP3) cause the autosomal-recessive skeletal disorder progressive pseudorheumatoid dysplasia (PPD). However, in mice there is no apparent phenotype caused by Wisp3 deficiency or overexpression. Consequently, the in vivo activities of Wisp3 have remained elusive. We cloned the zebrafish ortholog of Wisp3 and investigated its biologic activity in vivo using gain-of-function and loss-of-function approaches. Overexpression of zebrafish Wisp3 protein inhibited bone morphogenetic protein (BMP) and Wnt signaling in developing zebrafish. Conditioned medium-containing zebrafish and human Wisp3 also inhibited BMP and Wnt signaling in mammalian cells by binding to BMP ligand and to the Wnt coreceptors low-density lipoprotein receptor-related protein 6 (LRP6) and Frizzled, respectively. Wisp3 proteins containing disease-causing amino acid substitutions found in patients with PPD had reduced activity in these assays. Morpholino-mediated inhibition of zebrafish Wisp3 protein expression in developing zebrafish affected pharyngeal cartilage size and shape. These data provide a biologic assay for Wisp3, reveal a role for Wisp3 during zebrafish cartilage development, and suggest that dysregulation of BMP and/or Wnt signaling contributes to cartilage failure in humans with PPD.

CCN6 (WISP3) as a new regulator of the epithelial phenotype in breast cancer

CCN6 (WISP3) is a cysteine-rich secreted protein that belongs to the CCN (Cyr61, CTGF, Nov) family of genes. We found that CCN6 mRNA is reduced in 80% of cases of the most lethal form of locally advanced breast cancer, inflammatory breast cancer. CCN6 contains four highly conserved motifs with sequence similarities to insulin-like growth factor binding proteins, von Willebrand type C, thrombospondin 1, and a carboxyl-terminal domain putatively involved in dimerization. CCN6 has tumor growth-, proliferation-, and invasion-inhibitory functions in breast cancer. Recently, by using a small infering RNA to downregulate CCN6 in immortalized human mammary epithelial cells, CCN6 was found to be essential to induce the process of epithelial-mesenchymal transition (EMT) with repression of E-cadherin gene expression and induction of a protein expression program characteristic of EMT. This review will focus on the current knowledge regarding the function of CCN6 in breast cancer with special emphasis on the emerging role of CCN6 as a regulator of the epithelial phenotype and E-cadherin expression in the breast.

Differential Expression and Prognostic Implications of the CCN Family Members WISP-1, WISP-2, and WISP-3 in Human Breast Cancer

BACKGROUND

The CCN family has three Wnt-inducted secreted proteins named WISP-1, WISP-2 and WISP-3. These molecules are known to play a diverse role in cells, but their role in cancer cells remains controversial.

METHODS

In this study, we analyzed the expression of the three WISP molecules at the mRNA and protein levels in a cohort of 122 human breast tumors and 32 normal breast tissues, and we correlated these findings with patients' clinical outcomes.

RESULTS

WISP-1 transcripts were found in lower levels in node-positive tumors compared with node-negative tumors (P < .05); were lower in patients with a moderate (P = .01) and poor Nottingham Prognostic Index prognosis (P < .05) compared with good prognostic groups; were of significantly lower level in grade 3 differentiated tumors (P < .05) compared with grade 1; and were of lower levels in patients who developed metastasis and died from breast cancer-related causes (P < .05 in both comparisons). Almost the reverse was found to be true for WISP-2, which had greater levels of expression in node-positive tumors (P = .0043); higher levels in both moderate and poor prognostic groups compared with the good prognostic group (both P < .05); greater level in both grade 2 and 3 when compared with grade 1 (both P < .05); and higher levels in patients who went on to develop metastases (P < .01). WISP-3 transcript levels showed no statistically significant differences between groups.

CONCLUSIONS

WISPs may play important but contrasting roles in breast cancer. WISP-1 seems to act as a tumor suppressor and WISP-2 as a factor that stimulates aggressiveness; WISP-3 has no definable beneficial or detrimental role.

Expression and physiological role of CCN4/Wnt-induced secreted protein 1 mRNA splicing variants in chondrocytes

CCN4/Wnt-induced secreted protein 1 (WISP1) is one of the CCN (CTGF/Cyr61/Nov) family proteins. CCN members have typical structures composed of four conserved cysteine-rich modules and their variants lacking certain modules, generated by alternative splicing or gene mutations, have been described in various pathological conditions. Several previous reports described a CCN4/WISP1 variant (WISP1v) lacking the second module in a few malignancies, but no information concerning the production of WISP1 variants in normal tissue is currently available. The expression of CCN4/WISP1 mRNA and its variants were analyzed in a human chondrosarcoma-derived chondrocytic cell line, HCS-2/8, and primary rabbit growth cartilage (RGC) chondrocytes. First, we found WISP1v and a novel variant of WISP1 (WISP1vx) to be expressed in HCS-2/8, as well as full-length WISP1 mRNA. This new variant was lacking the coding regions for the second and third modules and a small part of the first module. To monitor the expression of CCN4/WISP1 mRNA along chondrocyte differentiation, RGC cells were cultured and sampled until they were mineralized. As a result, we identified a WISP1v ortholog in normal RGC cells. Interestingly, the WISP1v mRNA level increased dramatically along with terminal differentiation. Furthermore, overexpression of WISP1v provoked expression of an alkaline phosphatase gene that is a marker of terminal differentiation in HCS-2/8 cells. These findings indicate that WISP1v thus plays a critical role in chondrocyte differentiation toward endochondral ossification, whereas HCS-2/8-specific WISP1vx may be associated with the transformed phenotypes of chondrosarcomas.

Mutant WISP3 triggers the phenotype shift of articular chondrocytes by promoting sensitivity to IGF-1 hypothesis of spondyloepiphyseal dysplasia tarda with progressive arthropathy (SEDT-PA)

This article introduces the hypothesis that mutant WISP3 (Wnt1 inducible secreted protein-3) triggers the phenotype shift of the chondrocytes, especially in the articular chondrocytes, by promoting sensitivity to IGF-1 (insulin-like growth factor 1), and results in chondrocytes apoptosis in SEDT-PA. SEDT-PA is also referred to as progressive pseudorheumatoid dysplasia (PPD), arthropathy progressive pseudorheumatoid of childhood (APPRC). Evidence for the hypothesis is based on the following indications: (1) SEDT-PA is caused by mutations of the WISP3 gene. WISP3 encodes a domain that bears homology to the amino-terminal domain of the insulin-like growth factor binding proteins (IGFBPs). (2) IGF-1 enhances chondrocyte hypertrophy by insulin-like actions. WISP3 can up-regulate the expression of type II collagen. When chondrocytes become hypertrophic, they reduce the expression of types II and IX collagen. (3) The chondrocytes in the normal articular cartilage maintain a stable phenotype. These cells exhibit no mitotic activity, low matrix synthesis and low degradation. But articular chondrocytes could react to certain stimuli such as IGF-1. (4) The loss of WISP3 expression alters the phenotype of the breast epithelium and promotes motility and invasion. The WISP3-deficient cells are extremely sensitive to the growth stimulatory effects of IGF-1. (5) The action of IGF-I is inhibited by IGFBPs, both in articular chondrocytes and in the normal breast epithelium. In conclusion, the mutant WISP3 lose is the function of inhibiting IGF-1 and disturbs the maintenance of a stable phenotype in articular chondrocytes. So, the articular chondrocytes undergo hypertrophic and terminal differentiation apoptosis. The precise mechanism of WISP3 function during postnatal cartilage growth and homeostasis is not clear yet. This hypothesis provides a new clue on the present mechanism study on SEDT-PA. If verified, this new concept may lead to a novel pathogenesis of SEDT-PA.