Connective tissue growth factor confers drug resistance in breast cancer through concomitant up-regulation of Bcl-xL and cIAP1

Deregulated expression of connective tissue growth factor (CTGF/CCN2) is linked to poor outcome in human cancer

Connective tissue growth factor (CTGF/CCN2) has long been associated with human cancers. The role it plays in these neoplasms is diverse and tumour specific. Recurring patterns in clinical outcome, histological desmoplasia and mechanisms of action have been found. When CTGF is overexpressed compared to low-expressing normal tissue or is underexpressed compared to high-expressing normal tissue, the functional outcome favours tumour survival and disease progression. CTGF acts by altering proliferation, drug resistance, angiogenesis, adhesion and migration contributing to metastasis. The pattern of CTGF expression and tumour response helps to clarify the role of this matricellular protein across a multitude of human cancers.

CCN2 enhances resistance to cisplatin-mediating cell apoptosis in human osteosarcoma

Osteosarcoma (OS) is the most common form of malignant bone tumor and is an aggressive malignant neoplasm exhibiting osteoblastic differentiation. Cisplatin is one of the most efficacious antitumor drugs for osteosarcoma patients. However, treatment failures are common due to the development of chemoresistance. CCN2 (also known as CTGF), is a secreted protein that binds to integrins, modulates the invasive behavior of certain human cancer cells. However, the effect of CCN2 in cisplatin-mediated chemotherapy is still unknown. Here, we found that CCN2 was upregulated in human osteosarcoma cells after treatment with cisplatin. Moreover, overexpression of CCN2 increased the resistance to cisplatin-mediated cell apoptosis. In contrast, reduction of CCN2 by CCN2 shRNA promoted the chemotherapeutic effect of cisplatin. We also found that CCN2 provided resistance to cisplatin-induced apoptosis through upregulation of Bcl-xL and survivin. Knockdown of Bcl-xL or survivin removed the CCN2-mediated resistance to apoptosis induced by cisplatin. On the other hand, CCN2 also promoted FAK, MEK, and ERK survival signaling pathways to enhance tumor survival during cisplatin treatment. In a mouse xenograft model, overexpression of CCN2 promoted resistance to cisplatin. However, knockdown of CCN2 increased the therapeutic effect of cisplatin. Therefore, our data suggest that CCN2 might be a critical oncogene of human osteosarcoma for cisplatin-resistance and supported osteosarcoma cell growth in vivo and in vitro.

Knocking down the expression of adenylate cyclase-associated protein 1 inhibits the proliferation and migration of breast cancer cells

Adenylate cyclase-associated protein 1 (CAP1) is a conserved protein that was found to be up-regulated in breast cancer and related to the migration of breast cancer. We verified its roles in breast cancer specimens and cell lines. In our results, 71 of 100 specimens of breast cancer showed high levels of CAP1 by immunohistochemistry. Associated with statistical analysis, we saw that CAP1 was related to the grade of breast cancer. In MDA-MB-231, the expression of CAP1 was the highest and by knocking down the expression of CAP1 in MDA-MB-231, its ability for proliferating and migrating apparently decreased and induced changes in morphology, which were related to the arrangement of F-actin. Therefore, CAP1 might be a potential molecular targeted therapy for surgery and immune treatment.

Targeting connective tissue growth factor (CTGF) in acute lymphoblastic leukemia preclinical models: anti-CTGF monoclonal antibody attenuates leukemia growth

Connective tissue growth factor (CTGF/CCN2) is involved in extracellular matrix production, tumor cell proliferation, adhesion, migration, and metastasis. Recent studies have shown that CTGF expression is elevated in precursor B-acute lymphoblastic leukemia (ALL) and that increased expression of CTGF is associated with inferior outcome in B-ALL. In this study, we characterized the functional role and downstream signaling pathways of CTGF in ALL cells. First, we utilized lentiviral shRNA to knockdown CTGF in RS4;11 and REH ALL cells expressing high levels of CTGF mRNA. Silencing of CTGF resulted in significant suppression of leukemia cell growth compared to control vector, which was associated with AKT/mTOR inactivation and increased levels of cyclin-dependent kinase inhibitor p27. CTGF knockdown sensitized ALL cells to vincristine and methotrexate. Treatment with an anti-CTGF monoclonal antibody, FG-3019, significantly prolonged survival of mice injected with primary xenograft B-ALL cells when co-treated with conventional chemotherapy (vincristine, L-asparaginase and dexamethasone). Data suggest that CTGF represents a targetable molecular aberration in B-ALL, and blocking CTGF signaling in conjunction with administration of chemotherapy may represent a novel therapeutic approach for ALL patients.

IRS1 is highly expressed in localized breast tumors and regulates the sensitivity of breast cancer cells to chemotherapy, while IRS2 is highly expressed in invasive breast tumors

Insulin receptor substrate (IRS) proteins have been shown to play an important role in breast cancer by differentially regulating cancer cell survival, proliferation, and motility. Furthermore, the IL-4-induced tyrosine phosphorylation of the transcription factor STAT6 was shown to protect breast cancer cells from apoptosis. Here, we analyzed human breast cancer tissues for the expression of IRS1, IRS2, STAT6, and tyrosine phosphorylated STAT6 (pSTAT6). We found that IRS1 and pSTAT6 were both highly expressed in ductal carcinoma in situ (DCIS). On the other hand, IRS2 expression was low in DCIS, but increased significantly in relation to tumor invasiveness. We utilized cell lines with disparate IRS1 expression, MDA-MB-231, MCF7, and MCF7 cells with depleted IRS1 due to shRNA lentiviral infection, to examine the role of IRS1 and IRS2 in the responsiveness of breast cancer cells to chemotherapy. We report that high IRS1 sensitized MCF7 cells to specific chemotherapeutic agents. These results suggest that high IRS1 with low IRS2 expression may predict the effectiveness of specific types of chemotherapy in breast cancer.

Tumour-microenvironment interactions: role of tumour stroma and proteins produced by cancer-associated fibroblasts in chemotherapy response

BACKGROUND

Cytotoxic chemotherapy improves survival for some, but not all, cancer patients. Non-responders may experience unnecessary toxicity and cancer progression, thus creating an urgent need for biomarkers that can predict the response to chemotherapy. So far, the search for such biomarkers has primarily been focused on the cancer cells and less on their surrounding stroma. This stroma is known to act as a key regulator of tumour progression and, in addition, has been associated with drug delivery and drug efficacy. Fibroblasts represent the major cell type in cancer-associated stroma and they secrete extracellular matrix proteins as well as growth factors. This Medline-based literature review summarises the results from studies on epithelial cancers and aimed at investigating relationships between the quantity and quality of the intra-tumoral stroma, the cancer-associated fibroblasts, the proteins they produce and the concomitant response to chemotherapy. Biomarkers were selected for review that are known to affect cancer-related characteristics and patient prognosis.

RESULTS

The current literature supports the hypothesis that biomarkers derived from the tumour stroma may be useful to predict response to chemotherapy. This notion appears to be related to the overall quantity and cellularity of the intra-tumoural stroma and the predominant constituents of the extracellular matrix.

CONCLUSION

Increasing evidence is emerging showing that tumour-stroma interactions may not only affect tumour progression and patient prognosis, but also the response to chemotherapy. The tumour stroma-derived biomarkers that appear to be most appropriate to determine the patient's response to chemotherapy vary by tumour origin and the availability of pre-treatment tissue. For patients scheduled for adjuvant chemotherapy, the most promising biomarker appears to be the PLAU: SERPINE complex, whereas for patients scheduled for neo-adjuvant chemotherapy the tumour stroma quantity appears to be most relevant.

Breast tumor and stromal cell responses to TGF-β and hypoxia in matrix deposition

The components that comprise the extracellular matrix (ECM) are integral to normal tissue homeostasis as well as the development and progression of breast tumors. The secretion, construction, and remodeling of the ECM are each regulated by a complex interplay between tumor cells, fibroblasts and macrophages. Transforming growth factor-β (TGF-β) is an essential molecule in regulating the cellular production of ECM molecules and the adhesive interactions of cells with the ECM. Additionally, hypoxic cell signals, initiated by oxygen deprivation, additional metabolic factors or receptor activation, are associated with ECM formation and the progression of breast cancer. Both TGF-β and hypoxic cell signals are implicated in the functional and morphological changes of cancer-associated-fibroblasts and tumor-associated-macrophages. Moreover, the enhanced recruitment of tumor and stromal cells in response to hypoxia-induced chemokines leads to increased ECM deposition and remodeling, increased blood vessel formation, and enhanced tumor migration. Thus, elucidation of the collaborative networks between tumor and stromal cells in response to the combined signals of TGF-β and hypoxia may yield insight into treatment parameters that target both tumor and stromal cells.

Differential sensitivity to paclitaxel-induced apoptosis and growth suppression in paclitaxel-resistant cell lines established from HEC-1 human endometrial adenocarcinoma cells

To investigate acquired paclitaxel (PTX) resistance in cancer cells, we established five monoclonal PTX-resistant cell lines from HEC-1 human endometrial adenocarcinoma cells by means of long-term PTX-exposed cultures and limiting dilution cultures. The established PTX-resistant subclones showed apparent resistance to PTX-induced DNA fragmentation but not to PTX-induced growth suppression. None of the five PTX-resistant subclones showed apparent resistance to other anticancer drugs such as cisplatin, etoposide, 5-fluorouracil, pirarubicin-HCl, 4-hydroxy-cyclophosphamide or mitomycin C. Semiquantitative flow cytometric analysis revealed no apparent differential expression of 17 molecules that were previously reported to regulate apoptosis or drug resistance, between the five PTX-resistant subclones and the parent cells. Karyotyping analysis revealed common changes in chromosomes 4 and 18 in the five PTX-resistant subclones but not in the HEC-1 parent cells. These results indicate that PTX-induced growth suppression is regulated by different mechanisms from those involved in PTX-induced apoptosis. It was concluded that these established PTX-resistant subclones can be useful models in studies related to the prevention or treatment of recurrent cancers after PTX chemotherapy.

CTGF drives autophagy, glycolysis and senescence in cancer-associated fibroblasts via HIF1 activation, metabolically promoting tumor growth

Previous studies have demonstrated that loss of caveolin-1 (Cav-1) in stromal cells drives the activation of the TGF-β signaling, with increased transcription of TGF-β target genes, such as connective tissue growth factor (CTGF). In addition, loss of stromal Cav-1 results in the metabolic reprogramming of cancer-associated fibroblasts, with the induction of autophagy and glycolysis. However, it remains unknown if activation of the TGF-β / CTGF pathway regulates the metabolism of cancer-associated fibroblasts. Therefore, we investigated whether CTGF modulates metabolism in the tumor microenvironment. For this purpose, CTGF was overexpressed in normal human fibroblasts or MDA-MB-231 breast cancer cells. Overexpression of CTGF induces HIF-1α-dependent metabolic alterations, with the induction of autophagy/mitophagy, senescence, and glycolysis. Here, we show that CTGF exerts compartment-specific effects on tumorigenesis, depending on the cell-type. In a xenograft model, CTGF overexpressing fibroblasts promote the growth of co-injected MDA-MB-231 cells, without any increases in angiogenesis. Conversely, CTGF overexpression in MDA-MB-231 cells dramatically inhibits tumor growth in mice. Intriguingly, increased extracellular matrix deposition was seen in tumors with either fibroblast or MDA-MB-231 overexpression of CTGF. Thus, the effects of CTGF expression on tumor formation are independent of its extracellular matrix function, but rather depend on its ability to activate catabolic metabolism. As such, CTGF-mediated induction of autophagy in fibroblasts supports tumor growth via the generation of recycled nutrients, whereas CTGF-mediated autophagy in breast cancer cells suppresses tumor growth, via tumor cell self-digestion. Our studies shed new light on the compartment-specific role of CTGF in mammary tumorigenesis, and provide novel insights into the mechanism(s) generating a lethal tumor microenvironment in patients lacking stromal Cav-1. As loss of Cav-1 is a stromal marker of poor clinical outcome in women with primary breast cancer, dissecting the downstream signaling effects of Cav-1 are important for understanding disease pathogenesis, and identifying novel therapeutic targets.

Connective tissue growth factor in tumor pathogenesis

Key roles for connective tissue growth factor (CTGF/CCN2) are demonstrated in the wound repair process where it promotes myofibroblast differentiation and angiogenesis. Similar mechanisms are active in tumor-reactive stroma where CTGF is expressed. Other potential roles include prevention of hypoxia-induced apoptosis and promoting epithelial-mesenchymal transistion (EMT). CTGF expression in tumors has been associated to both tumor suppression and progression. For example, CTGF expression in acute lymphoblastic leukemia, breast, pancreas and gastric cancer correlates to worse prognosis whereas the opposite is true for colorectal, lung and ovarian cancer. This discrepancy is not yet understood. High expression of CTGF is a hallmark of ileal carcinoids, which are well-differentiated endocrine carcinomas with serotonin production originating from the small intestine and proximal colon. These tumors maintain a high grade of differentiation and low proliferation. Despite this, they are malignant and most patients have metastatic disease at diagnosis. These tumors demonstrate several phenotypes potentially related to CTGF function namely: cell migration, absent tumor cell apoptosis, as well as, reactive and well vascularised myofibroblast rich stroma and fibrosis development locally and in distal organs. The presence of CTGF in other endocrine tumors indicates a role in the progression of well-differentiated tumors.

Insulin receptor substrate 1 expression enhances the sensitivity of 32D cells to chemotherapy-induced cell death

The adapters IRS1 and IRS2 link growth factor receptors to downstream signaling pathways that regulate proliferation and survival. Both suppress factor-withdrawal-induced apoptosis and have been implicated in cancer progression. However, recent studies suggest IRS1 and IRS2 mediate differential functions in cancer pathogenesis. IRS1 promoted breast cancer proliferation, while IRS2 promoted metastasis. The role of IRS1 and IRS2 in controlling cell responses to chemotherapy is unknown. To determine the role of IRS1 and IRS2 in the sensitivity of cells to chemotherapy, we treated 32D cells lacking or expressing IRS proteins with various concentrations of chemotherapeutic agents. We found that expression of IRS1, in contrast to IRS2, enhanced the sensitivity of 32D cells to chemotherapy-induced apoptosis. When IRS2 was expressed with IRS1, the cells no longer showed enhanced sensitivity. Expression of IRS1 did not alter the expression of pro- and anti-apoptotic proteins; however, 32D-IRS1 cells expressed higher levels of Annexin A2. In 32D-IRS1 cells, IRS1 and Annexin A2 were both located in cytoplasmic and membrane fractions. We also found that IRS1 coprecipitated with Annexin A2, while IRS2 did not. Decreasing Annexin A2 levels reduced 32D-IRS1 cell sensitivity to chemotherapy. These results suggest IRS1 enhances sensitivity to chemotherapy in part through Annexin A2.

Potential for modulation of the fas apoptotic pathway by epidermal growth factor in sarcomas

One important mechanism by which cancer cells parasitize their host is by escaping apoptosis. Thus, selectively facilitating apoptosis is a therapeutic mechanism by which oncotherapy may prove highly advantageous. One major apoptotic pathway is mediated by Fas ligand (FasL). The death-inducing signaling Ccmplex (DISC) and subsequent death-domain aggregations are created when FasL is bound by its receptor thereby enabling programmed cell death. Conceptually, if a better understanding of the Fas pathway can be garnered, an oncoselective prodeath therapeutic approach can be tailored. Herein, we propose that EGF and CTGF play essential roles in the regulation of the Fas apoptotic pathway in sarcomas. Tumor and in vitro data suggest viable cells counter the prodeath signal induced by FasL by activating EGF, which in turn induces prosurvival CTGF. The prosurvival attributes of CTGF ultimately predominate over the death-inducing FasL. Cells destined for elimination inhibit this prosurvival response via a presently undefined pathway. This scenario represents a novel role for EGF and CTGF as regulators of the Fas pathway in sarcomas.

Taking aim at the extracellular matrix: CCN proteins as emerging therapeutic targets

Members of the CCN family of matricellular proteins are crucial for embryonic development and have important roles in inflammation, wound healing and injury repair in adulthood. Deregulation of CCN protein expression or activities contributes to the pathobiology of various diseases - many of which may arise when inflammation or tissue injury becomes chronic - including fibrosis, atherosclerosis, arthritis and cancer, as well as diabetic nephropathy and retinopathy. Emerging studies indicate that targeting CCN protein expression or signalling pathways holds promise in the development of diagnostics and therapeutics for such diseases. This Review summarizes the biology of CCN proteins, their roles in various pathologies and their potential as therapeutic targets.

Discovery of IL-18 as a novel secreted protein contributing to doxorubicin resistance by comparative secretome analysis of MCF-7 and MCF-7/Dox

Background

Resistance to chemotherapy is the major cause of failure in breast cancer treatment. Recent studies suggest that secreted proteins may play important roles in chemoresistance. We sought to systematically characterize secreted proteins associated with drug resistance, which may represent potential serum biomarkers or novel drug targets.

Methodology/Principal Findings

In the present work, we adopted the proteomic strategy of one-dimensional gel electrophoresis followed by liquid chromatography-tandem mass spectrometry to compare the secretome of MCF-7 and doxorubicin-resistant MCF-7/Dox. A total of 2,084 proteins were identified with at least two unique peptides in the conditioned media of two cell lines. By quantification with label-free spectral counting, 89 differentially expressed secreted proteins (DESPs) between the two cell lines were found. Among them, 57 DESPs were first found to be related to doxorubicin resistance in this work, including 24 extracellular matrix related proteins, 2 cytokines and 31 unclassified proteins. We focused on 13 novel DESPs with confirmed roles in tumor metastasis. Among them, the elevated expression of IL-18 in doxorubicin-resistant cell lines and breast tumor tissues was validated and its role in doxorubicin resistance was further confirmed by cell viability experiments in the presence or absence of this protein.

Conclusions/Significance

Comparative analysis of the secretome of MCF-7 and MCF-7/Dox identified novel secreted proteins related to chemotherapy resistance. IL-18 was further validated to contribute to doxorubicin resistance, in addition to its confirmed role in breast cancer metastasis. Due to its dual roles in both drug resistance and tumor metastasis, IL-18 may represent a useful drug target for breast cancer therapy.

From cancer metabolism to new biomarkers and drug targets

Great interest is presently given to the analysis of metabolic changes that take place specifically in cancer cells. In this review we summarize the alterations in glycolysis, glutamine utilization, fatty acid synthesis and mitochondrial function that have been reported to occur in cancer cells and in human tumors. We then propose considering cancer as a system-level disease and argue how two hallmarks of cancer, enhanced cell proliferation and evasion from apoptosis, may be evaluated as system-level properties, and how this perspective is going to modify drug discovery. Given the relevance of the analysis of metabolism both for studies on the molecular basis of cancer cell phenotype and for clinical applications, the more relevant technologies for this purpose, from metabolome and metabolic flux analysis in cells by Nuclear Magnetic Resonance and Mass Spectrometry technologies to positron emission tomography on patients, are analyzed. The perspectives offered by specific changes in metabolism for a new drug discovery strategy for cancer are discussed and a survey of the industrial activity already going on in the field is reported.

Expression of connective tissue growth factor (CTGF/CCN2) in breast cancer cells is associated with increased migration and angiogenesis

Connective tissue growth factor (CTGF/CCN2) belongs to the CCN family of matricellular proteins, comprising Cyr61, CTGF, NovH and WISP1-3. The CCN proteins contain an N-terminal signal peptide followed by four conserved domains sharing sequence similarities with the insulin-like growth factor binding proteins, von Willebrand factor type C repeat, thrombospondin type 1 repeat, and a C-terminal growth factor cysteine knot domain. To investigate the role of CCN2 in breast cancer, we transfected MCF-7 cells with full-length CCN2, and with four mutant constructs in which one of the domains had been deleted. MCF-7 cells stably expressing full-length CCN2 demonstrated reduced cell proliferation, increased migration in Boyden chamber assays and promoted angiogenesis in chorioallantoic membrane assays compared to control cells. Deletion of the C-terminal cysteine knot domain, but not of any other domain-deleted mutants, abolished activities mediated by full-length CCN2. We have dissected the role of CCN2 in breast tumorigenesis on a structural basis.

CTGF is overexpressed in papillary thyroid carcinoma and promotes the growth of papillary thyroid cancer cells

Connective tissue growth factor (CTGF or CCN2), which belongs to the CCN family, is a secreted protein. It has been implicated in various biological processes, such as cell proliferation, migration, angiogenesis, and tumorigenesis. In this study, we found that CTGF expression level was elevated in primary papillary thyroid carcinoma (PTC) samples and correlated with clinical features, such as metastasis, tumor size, and clinical stage. Overexpression of CTGF in PTC cells accelerated their growth in liquid culture and soft agar as well as protecting PTC cells from apoptosis induced by IFN-gamma treatment. Downregulation of CTGF in PTC cells inhibits cell growth in liquid culture and soft agar and induces the activation of caspase pathway and sensitized PTC cells to apoptosis. Our data suggest that CTGF plays an important role in PTC progression by supporting tumor cell survival and drug resistance, and CTGF may be used as a potential tumor marker for PTC diagnosis.

Taxol resistance in breast cancer cells is mediated by the hippo pathway component TAZ and its downstream transcriptional targets Cyr61 and CTGF

Taxol (paclitaxel) resistance represents a major challenge in breast cancer treatment. The TAZ (transcriptional co-activator with PDZ-binding motif) oncogene is a major component of the novel Hippo-LATS signaling pathway and a transcriptional coactivator that interacts with and activates multiple transcription factors to regulate various biological processes. Here, we report that elevated levels of TAZ found in human breast cancer cells are responsible for their resistance to Taxol. DNA microarray analysis identified the oncogenes Cyr61 and CTGF as downstream transcriptional targets of TAZ. Short hairpin RNA-mediated knockdown of both Cyr61 and CTGF reversed TAZ-induced Taxol resistance in breast cancer cells. Interaction of TAZ with the TEAD family of transcription factors was essential for TAZ to activate the Cyr61/CTGF promoters and to induce Taxol resistance. Our findings define the TAZ-TEAD-Cyr61/CTGF signaling pathway as an important modifier of the Taxol response in breast cancer cells, as well as highlighting it as a novel therapeutic target to treat drug-resistant breast cancers that arise commonly at advanced stages of disease.

CCN2/CTGF silencing blocks cell aggregation in embryonal carcinoma P19 cell

Connective tissue growth factor (CCN2/CTGF) is a matricellular-secreted protein involved in extracellular matrix remodeling. The P19 cell line is an embryonic carcinoma line widely used as a cellular model for differentiation and migration studies. In the present study, we employed an exogenous source of CCN2 and small interference RNA to address the role of CCN2 in the P19 cell aggregation phenomenon. Our data showed that increasing CCN2 protein concentrations from 0.1 to 20 nM decreased the number of cell clusters and dramatically increased cluster size without changing proliferation or cell survival, suggesting that CCN2 induced aggregation. In addition, CCN2 specific silencing inhibited typical P19 cell aggregation, which could be partially rescued by 20 nM CCN2. The present study demonstrates that CCN2 is a key molecule for cell aggregation of embryonic P19 cells.

Significance of serum connective tissue growth factor in patients with hepatocellular carcinoma and relationship with angiogenesis

BACKGROUND

Connective tissue growth factor (CTGF) expression changes variously in different human malignancies. The role of CTGF in hepatocellular carcinoma (HCC) is still not clear. The purpose of this study was to investigate the role of serum CTGF in patients with HCC and its correlation with HCC angiogenesis.

METHODS

CTGF, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) were measured by ELISA in preoperative sera of 88 patients with HCC with tumor resection and 39 healthy subjects. The relationship between CTGF and HCC clinicopathological parameters was observed. Prognostic significance of CTGF for survival of patients with HCC was assessed by Kaplan-Meier analysis.

RESULTS

Preoperative serum CTGF level was significantly higher in patients with HCC than in healthy subjects (median, 63.5 vs. 11.4 ng/ml; P < 0.001). Serum CTGF correlated significantly with a series of clinicopathological parameters (big tumor size, advanced pathological tumor-node-metastasis stage, absence of tumor capsule, portal vein invasion). Serum CTGF showed a significant correlation with disease-free survival and overall survival of patients with HCC. Patients with high serum CTGF (>63.5 ng/ml) had a poorer disease-free survival time than the others (CTGF < or = 63.5 ng/ml; median disease-free survival time, 9.6 vs. 19.3 months). Patients with high serum CTGF had poorer overall survival time (median, 13.1 months) than the others (median, 21.7 months). In multivariate Cox analysis, CTGF was identified as an independent and significant prognostic factor of survival of HCC patients.

CONCLUSIONS

Serum CTGF plays an important role in the progression of HCC. Serum CTGF may be a potential indicator of angiogenesis of HCC.

Targeting YAP and Hippo signaling pathway in liver cancer

IMPORTANCE OF THE FIELD

The Hippo signaling pathway plays pivotal roles in controlling both cell growth and organ size, emerging as a new paradigm in tumor suppression. Yes-associated protein (YAP) functions as a potent transcription co-activator and is a major downstream target tightly regulated by the Hippo pathway. Inactivation of the Hippo signaling induces YAP-mediated activation of various target genes that functionally causes cellular proliferation and outgrowth of organ size. Recently, YAP has been implicated as a bona fide oncogene in solid tumors, but little is known about its exact molecular mechanism in carcinogenesis.

AREAS COVERED IN THIS REVIEW

We discuss the latest important findings in the Hippo signaling pathway and the possible means of developing potential cancer therapeutics by targeting multiple sites along the Hippo pathway.

WHAT THE READER WILL GAIN

An overview of the emerging roles of YAP and Hippo signaling in oncogenesis and the possible ways of developing cancer therapies against the pathway components, downstream targets or interconnected pathways.

TAKE HOME MESSAGE

YAP is a key oncogenic driver in liver carcinogenesis and deregulation of the Hippo pathway causes tumor formation and malignancy. Targeting YAP and cognate downstream signaling targets may have clinical utility in cancer therapies.

Connective tissue growth factor associated with oncogenic activities and drug resistance in glioblastoma multiforme

Connective tissue growth factor (CTGF or CCN2) is a secreted protein that belongs to the CCN [cysteine-rich CYR61/CTGF/nephroblastoma-overexpressed gene] family. These proteins have been implicated in various biological processes, including stimulation of cell proliferation, migration, angiogenesis and tumorigenesis. In a previous study, we found that CTGF mRNA was elevated in primary gliomas, and a significant correlation existed between CTGF mRNA levels versus tumor grade, histology and patient survival. In this study, the role of CTGF in glioma tumorigenesis was explored. Forced expression of CTGF in glioblastoma multiforme (GBM) cells accelerated their growth in liquid culture and soft agar, stimulated cells migration in Boyden chamber assays and significantly increased their ability to form large, vascularized tumors in nude mice. CTGF induced the expression of the antiapoptotic proteins, Bcl-xl, Survivin and Flip. Overexpression of CTGF caused the U343 GBM cells to survive for longer than 40 days in serum-free medium and resist antitumor drugs including tumor necrosis factor (TNF), TNF-related apoptosis-inducing ligand, VELCADE (bortezomib, proteasome inhibitor) and temozolomide. Our data suggest that CTGF plays an important role in glioma progression, by supporting tumor cells survival and drug resistance.

Iodine induces apoptosis via regulating MAPKs-related p53, p21, and Bcl-xL in thyroid cancer cells

Thyroid cancer is the most common endocrine malignancy and exhibits the full range of malignant behaviors from the relatively indolent occult differentiated thyroid cancer to uniformly aggressive and lethal anaplastic thyroid cancer. Iodine is a well known key element in thyroid normal function maintenance and thyroid cancer development. However, the effects induced by iodine and the molecular mechanisms involved remain poorly understood in thyroid cancer. We investigated the apoptotic effect of iodine on three different subtypes of thyroid cancer cells. We observed that apoptosis induced by iodine was mitochondrial-mediated. Iodine treatment decreased the level of mutant p53 including the R273H mutant that possesses anti-apoptotic features, but increased the p21 level. Surprisingly, high doses of iodine promoted instead of suppressed the expression of anti-apoptotic protein Bcl-xL expression. Moreover, iodine transiently activated the subfamily members of mitogen activated protein kinases (MAPKs) (ERK1/2, p38 and JNK1/2) which contribute to modulate p53, p21 and Bcl-xL expression. The further results showed the three subfamily members of MAPKs all worked as anti-apoptotic factors. Collectively, iodine-induced apoptotic pathway is involved in the activation of MAPKs-related p21, Bcl-xL and mutant p53 regulation. The findings provide solid molecular evidence to explain the potential pathway for iodine to influence thyroid cancer development. It may also reveal some novel molecular targets for the treatment of thyroid cancer.