Receptor for hyaluronan-mediated motility isoform B promotes liver metastasis in a mouse model of multistep tumorigenesis and a tail vein assay for metastasis

CD44 and RHAMM Are Microenvironmental Sensors with Dual Metastasis Promoter and Suppressor Functions

The progression of primary tumors to metastases remains a significant roadblock to the treatment of most cancers. Emerging evidence has identified genes that specifically affect metastasis and are potential therapeutic targets for managing tumor progression. However, these genes can have dual tumor promoter and suppressor functions that are contextual in manifestation, and that complicate their development as targeted therapies. CD44 and RHAMM/HMMR are examples of multifunctional proteins that can either promote or suppress metastases, as demonstrated in experimental models. These two proteins can be viewed as microenvironmental sensors and this minireview addresses the known mechanistic underpinnings that may determine their metastasis suppressor versus promoter functions. Leveraging this mechanistic knowledge for CD44, RHAMM, and other multifunctional proteins is predicted to improve the precision of therapeutic targeting to achieve more effective management of metastasis.

Hyaluronic acid metabolism and chemotherapy resistance: recent advances and therapeutic potential

Hyaluronic acid (HA) is a major component of the extracellular matrix, providing essential mechanical scaffolding for cells and, at the same time, mediating essential biochemical signals required for tissue homeostasis. Many solid tumors are characterized by dysregulated HA metabolism, resulting in increased HA levels in cancer tissues. HA interacts with several cell surface receptors, such as cluster of differentiation 44 and receptor for hyaluronan-mediated motility, thus co-regulating important signaling pathways in cancer development and progression. In this review, we describe the enzymes controlling HA metabolism and its intracellular effectors emphasizing their impact on cancer chemotherapy resistance. We will also explore the current and future prospects of HA-based therapy, highlighting the opportunities and challenges in the field.

Bcl-xL is translocated to the nucleus via CtBP2 to epigenetically promote metastasis

Besides its mitochondria-based anti-apoptotic role, Bcl-xL also travels to the nucleus to promote cancer metastasis by upregulating global histone H3 trimethyl Lys4 (H3K4me3) and TGFβ transcription. How Bcl-xL is translocated into the nucleus and how nuclear Bcl-xL regulates H3K4me3 modification are not understood. Here, we report that C-terminal Binding Protein 2 (CtBP2) binds Bcl-xL via its N-terminus and translocates Bcl-xL into the nucleus. Knockdown of CtBP2 by shRNA decreases the nuclear portion of Bcl-xL and reverses Bcl-xL-induced cell migration and metastasis in mouse models. Furthermore, knockout of CtBP2 suppresses Bcl-xL transcription. The binding between Bcl-xL and CtBP2 is required for their interaction with MLL1, a histone H3K4 methyltransferase. Pharmacologic inhibition of MLL1 enzymatic activity reverses Bcl-xL-induced H3K4me3 and TGFβ mRNA upregulation as well as cell invasion. Moreover, cleavage under targets and release using nuclease (CUT&RUN) coupled with next generation sequencing reveals that H3K4me3 modifications are particularly enriched in the promotor region of genes encoding TGFβ and its signaling pathway in the cancer cells overexpressing Bcl-xL. Altogether, the metastatic function of Bcl-xL is mediated by its interaction with CtBP2 and MLL1.

Hyaluronan in liver fibrosis: basic mechanisms, clinical implications, and therapeutic targets

Hyaluronan (HA), also known as hyaluronic acid, is a glycosaminoglycan that is a critical component of the extracellular matrix (ECM). Production and deposition of ECM is a wound-healing response that occurs during chronic liver disease, such as cirrhosis. ECM production is a sign of the disease progression of fibrosis. Indeed, the accumulation of HA in the liver and elevated serum HA levels are used as biomarkers of cirrhosis. However, recent studies also suggest that the ECM, and HA in particular, as a functional signaling molecule, facilitates disease progression and regulation. The systemic and local levels of HA are regulated by de novo synthesis, cleavage, endocytosis, and degradation of HA, and the molecular mass of HA influences its pathophysiological effects. However, the regulatory mechanisms of HA synthesis and catabolism and the functional role of HA are still poorly understood in liver fibrosis. This review summarizes the role of HA in liver fibrosis at molecular levels as well as its clinical implications and discusses the potential therapeutic uses of targeting HA in liver fibrosis.

Low-dose carbon monoxide suppresses metastatic progression of disseminated cancer cells

Low-dose carbon monoxide (CO) is under investigation in clinical trials to treat non-cancerous diseases and has excellent safety profiles. Due to the early detection and cancer awareness, increasing cancer patients are diagnosed at early stages and potentially curative surgical resection can be done. However, many patients ultimately experience recurrence. Here, we evaluate the therapeutic effect of CO on cancer metastatic progression. We show that 250 ppm CO inhibits migration of multiple types of cancer cell lines including breast, pancreatic, colon, prostate, liver, and lung cancer and reduces the ability to adhere to fibronectin. We demonstrate that in mouse models, 250 ppm inhaled CO inhibits lung metastasis of breast cancer and liver metastasis of pancreatic cancer. Moreover, low-dose CO suppresses recurrence and increases survival after surgical removal of primary pancreatic cancer in mice. Mechanistically, low-dose CO blocks transcription of heme importers, leading to diminished intracellular heme levels and a heme-regulated enzyme, cytochrome P4501B1 (CYP1B1). Either supplementing heme or overexpressing CYP1B1 reverses the anti-migration effect of low-dose CO. Taken together, low-dose CO therapy inhibits cell migration, reduces adhesion to fibronectin, prevents disseminated cancer cells from expanding into gross metastases, and improves survival in pre-clinical mouse models of metastasis.

Ultrasound-targeted microbubble destruction-mediated silencing of FBXO11 suppresses development of pancreatic cancer

Ultrasound-targeted microbubble destruction (UTMD) has been a promising noninvasive tool for organ- or tissue-specific gene or drug delivery. This study aimed to explore the function of F-box protein 11 (FBXO11), an E3 ubiquitin ligase, in the development of pancreatic cancer (PCa). Differentially expressed genes in PCa were identified using the GSE62452 and GSE28735 datasets, and FBXO11 was significantly highly expressed in PCa. UTMD-mediated FBXO11 silencing significantly suppressed growth activity, epithelial-mesenchymal transition, migration, and invasion while reduced apoptosis of PCa cells in vitro and reduced the growth and metastasis of xenograft tumors in vivo. Importantly, UTMD-mediated sh-FBXO11 showed more pronounced tumor-suppressive effects than direct administration of sh-FBXO11 alone. The potential substrates of FBXO11 as an E3 ubiquitin ligase were predicted using the Ubibrowser. TP53 was predicted and validated as a downstream substrate of FBXO11. FBXO11 induced ubiquitination and degradation of the tumor suppressor protein TP53 to induce PCa progression. In conclusion, this study suggests that silencing of FBXO11, especially that mediated by UTMD, might suppress the malignant biological behaviors of PCa cells and serve as a potential therapeutic strategy for PCa management.

Serum Proteins, HMMR, NXPH4, PITX1 and THBS4; A Panel of Biomarkers for Early Diagnosis of Hepatocellular Carcinoma

The high morbidity rate of hepatocellular carcinoma (HCC) is mainly linked to late diagnosis. Early diagnosis of this leading cause of mortality is therefore extremely important. We designed a gene selection strategy to identify potential secretory proteins by predicting signal peptide cleavage sites in amino acid sequences derived from transcriptome data of human multistage HCC comprising chronic hepatitis, liver cirrhosis and early and overt HCCs. The gene selection process was validated by the detection of molecules in the serum of HCC patients. From the computational approaches, 10 gene elements were suggested as potent candidate secretory markers for detecting HCC patients. ELISA testing of serum showed that hyaluronan mediated motility receptor (HMMR), neurexophilin 4 (NXPH4), paired like homeodomain 1 (PITX1) and thrombospondin 4 (THBS4) are early-stage HCC diagnostic markers with superior predictive capability in a large cohort of HCC patients. In the assessment of differential diagnostic accuracy, receiver operating characteristic curve analyses showed that HMMR and THBS4 were superior to α-fetoprotein (AFP) in diagnosing HCC, as evidenced by the high area under the curve, sensitivity, specificity, accuracy and other values. In addition, comparative analysis of all four markers and AFP combinations demonstrated that HMMR-PITX1-AFP and HMMR-NXPH4-PITX1 trios were the optimal combinations for reaching 100% accuracy in HCC diagnosis. Serum proteins HMMR, NXPH4, PITX1 and THBS4 can complement measurement of AFP in diagnosing HCC and improve identification of patients with AFP-negative HCC as well as discriminate HCC from non-malignant chronic liver disease.

RHAMMB-mediated bifunctional nanotherapy targeting Bcl-xL and mitochondria for pancreatic neuroendocrine tumor treatment

The incidence of pancreatic neuroendocrine tumor (PNET) has continued to rise. Due to their indolent feature, PNET patients often present with incurable, metastatic diseases. Novel therapies are urgently needed. We have previously shown that Receptor for Hyaluronic Acid-Mediated Motility isoform B (RHAMM^B) and Bcl-xL are upregulated in PNETs and both of them promote PNET metastasis. Because RHAMM protein is undetectable in most adult tissues, we hypothesized that RHAMM^B could be a gateway for nanomedicine delivery into PNETs. To test this, we developed a RHAMM^B-targeting nanoparticle (NP). Inside this NP, we assembled small interfering RNA (siRNA) against Bcl-xL (siBcl-xL) and mitochondria-fusing peptide KLA. We demonstrated that RHAMM^B-positive PNETs picked up the RHAMM^B-targeting NPs. siBcl-xL or KLA alone killed only 30% of PNET cells. In contrast, a synergistic killing effect was achieved with the co-delivery of siBcl-xL and KLA peptide in vitro. Unexpectedly, siBcl-xL induced cell death before reducing Bcl-xL protein levels. The systemically injected RHAMM^B-targeting NPs carrying siBcl-xL and KLA peptide significantly reduced tumor burden in mice bearing RHAMM^B-positive PNETs. Together, these findings indicate that the RHAMM^B-targeting nanotherapy serves as a promising drug delivery system for PNET and possibly other malignancies with upregulated RHAMM^B. The combination of siBcl-xL and KLA peptide can be a therapy for PNET treatment.

The Impact of Hyaluronic Acid on Tendon Physiology and Its Clinical Application in Tendinopathies

The physical-chemical, structural, hydrodynamic, and biological properties of hyaluronic acid within tendons are still poorly investigated. Medical history and clinical applications of hyaluronic acid for tendinopathies are still debated. In general, the properties of hyaluronic acid depend on several factors including molecular weight. Several preclinical and clinical experiences show a good efficacy and safety profile of hyaluronic acid, despite the absence of consensus in the literature regarding the classification according to molecular weight. In in vitro and preclinical studies, hyaluronic acid has shown physical-chemical properties, such as biocompatibility, mucoadhesivity, hygroscopicity, and viscoelasticity, useful to contribute to tendon healing. Additionally, in clinical studies, hyaluronic acid has been used with promising results in different tendinopathies. In this narrative review, findings encourage the clinical application of HA in tendinopathies such as rotator cuff, epicondylitis, Achilles, and patellar tendinopathy.

RHAMM Is a Multifunctional Protein That Regulates Cancer Progression

The functional complexity of higher organisms is not easily accounted for by the size of their genomes. Rather, complexity appears to be generated by transcriptional, translational, and post-translational mechanisms and tissue organization that produces a context-dependent response of cells to specific stimuli. One property of gene products that likely increases the ability of cells to respond to stimuli with complexity is the multifunctionality of expressed proteins. Receptor for hyaluronan-mediated motility (RHAMM) is an example of a multifunctional protein that controls differential responses of cells in response-to-injury contexts. Here, we trace its evolution into a sensor-transducer of tissue injury signals in higher organisms through the detection of hyaluronan (HA) that accumulates in injured microenvironments. Our goal is to highlight the domain and isoform structures that generate RHAMM's function complexity and model approaches for targeting its key functions to control cancer progression.

High levels of truncated RHAMM cooperate with dysfunctional p53 to accelerate the progression of pancreatic cancer

Pancreatic cancer has the lowest survival rate out of all types of cancer. Pancreatic cancer patients are often diagnosed at advanced stages, hence an urgent need for a better therapeutic development of this devastating disease. Receptor for hyaluronan-mediated motility (RHAMM), not expressed in adult normal pancreas, has been suggested as a prognostic factor and a potential therapeutic target for pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine tumor (PNET). In this study, we initially sought to determine whether genetic deletion of RHAMM would slow down pancreatic cancer progression using Rhamm^-/- mice. However, we found that Rhamm^-/- mice expressed a truncated HMMR^Δexon8-16 protein at higher abundance levels than wild-type RHAMM. While HMMR^Δexon8-16 did not enable malignant progression of pancreatic intraepithelial neoplasia in p48-Cre; LSL-KRAS^G12D mice, it accelerated the formation of invasive PDAC and shortened the survival of p48-Cre; LSL-KRAS^G12D mice with heterozygous p53 knockout. Kras^G12D PDAC mice with homozygous p53 knockout mice died around 10 weeks, and the effect of HMMR^Δexon8-16 was not apparent in these short lifespan mice. In addition, HMMR^Δexon8-16 shortened the survival of PNET-bearing RIP-Tag mice, which had inactivated p53. In our analysis of TCGA dataset, pancreatic cancer patients with mutant TP53 or loss of one copy of TP53 had higher RHAMM expression, which, combined, predicted worse outcomes. Taken together, by collaborating with dysfunctional p53, high levels of HMMR^Δexon8-16 , which lacks the centrosome targeting domain and degrons for interaction with the Anaphase-Promoting Complex (APC), accelerated pancreatic cancer progression.

Expression of the Receptor for Hyaluronic Acid-Mediated Motility (RHAMM) in Endometrial Cancer is Associated With Adverse Histologic Parameters and Tumor Progression

Endometrial cancer is one of the most common gynecologic malignancies worldwide. Only 2 agents have been approved by Food and Drug Administration for endometrial cancer since 1971. There is a need to identify molecular targets to treat advanced endometrial cancer. The receptor for hyaluronic acid-mediated motility (RHAMM) is upregulated in various types of cancer. Here, we aimed to determine the clinical significance of RHAMM expression in endometrial cancer. Two hundred twenty-five cases of endometrial cancer, including serous and endometrioid types, and 8 cases of normal endometrium were used for studying RHAMM protein levels. The Cancer Genome Atlas database was also queried for RHAMM mRNA expression in endometrial cancer. Increased expression of RHAMM protein was seen in endometrial cancer compared with no or weak expression in normal endometrium. RHAMM expression positively correlated with tumor grade. RHAMM expression was significantly increased in endometrial serous carcinomas, which are high-grade, aggressive types of endometrial cancer, compared with the relatively less aggressive endometrioid carcinomas. RHAMM expression also correlated with the presence of lymphovascular invasion. RHAMM mRNA expression correlated with decreased survival in The Cancer Genome Atlas cohort. Therefore, increased RHAMM expression in endometrial cancer is associated with high-grade tumors and is indicative of more aggressive behavior. These findings suggest RHAMM as a prognostic factor in endometrial cancer and as a potential therapeutic target in advanced endometrial cancer for future studies.

Co-localization and crosstalk between CD44 and RHAMM depend on hyaluronan presentation

CD44 and the receptor for hyaluronic acid-mediated motility (RHAMM) are the main hyaluronan (HA) receptors. They are commonly overexpressed in different cancers activating signaling pathways related to tumor progression, metastasis and chemoresistance. Besides their involvement in signal transduction via interaction with HA, currently, there is a little information about the possible crosstalk between CD44 and RHAMM and the role of HA in this process. In the present work, we used immunocytochemistry combined with Förster resonance energy transfer (FRET) microscopy and co-immunoprecipitation to elucidate the involvement of HA in CD44 and RHAMM expression, co-localization and crosstalk. We studied breast cancer cells lines with different degrees of invasiveness and expression of these receptors in the absence of exogenous HA and compared the data with the results obtained for cultures supplemented with either soluble HA or seeded on substrates with end-on immobilized HA. Our results demonstrated that cells response depends on the HA presentation: CD44/RHAMM complexation was upregulated in all cell lines upon interaction with immobilized HA, but not with its soluble form. Moreover, the results showed that the expression of both CD44 and RHAMM is regulated via interactions with HA indicating cell-specific feedback loop(s) in the signaling cascade.

Function-Blocking RHAMM Peptides Attenuate Fibrosis and Promote Antifibrotic Adipokines in a Bleomycin-Induced Murine Model of Systemic Sclerosis

Systemic sclerosis a chronic, fibrotic disorder associated with high disease-specific mortality and morbidity. Cutaneous manifestations include dermal thickening and obliteration of dermal adipose tissue. Accumulation of low-molecular-weight hyaluronan, which signals through the receptor for hyaluronan-mediated motility, RHAMM, leads to progressive fibrosis and is correlated with increased severity of systemic sclerosis. The purpose of this study is to test the efficacy of two function-blocking RHAMM peptides, NPI-110 and NPI-106, in reducing skin fibrosis in a bleomycin-induced mouse model of systemic sclerosis. NPI-110 reduced visible measures of fibrosis (dermal thickness and collagen production, deposition, and organization) and profibrotic gene expression (Tgfb1, c-Myc, Col1a1, Col3a1). NPI-110 treatment also increased the expression of the antifibrotic adipokines perilipin and adiponectin. Both RHAMM peptides strongly reduced dermal RHAMM expression, predicting that dermal fibroblasts are peptide targets. Transcriptome and cell culture analyses using Rhamm-/- and Rhamm-rescued dermal fibroblasts reveal a TGFβ1/RHAMM/MYC signaling axis that promotes fibrogenic gene expression and myofibroblast differentiation. RHAMM function‒blocking peptides suppress this signaling and prevent TGFβ1-induced myofibroblast differentiation. These results suggest that inhibiting RHAMM signaling will offer a treatment method for cutaneous fibrosis in systemic sclerosis.

SCNrank: spectral clustering for network-based ranking to reveal potential drug targets and its application in pancreatic ductal adenocarcinoma

Background

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic malignancy. Due to its wide heterogeneity, PDAC acts aggressively and responds poorly to most chemotherapies, causing an urgent need for the development of new therapeutic strategies. Cell lines have been used as the foundation for drug development and disease modeling. CRISPR-Cas9 plays a key role in every step-in drug discovery: from target identification and validation to preclinical cancer cell testing. Using cell-line models and CRISPR-Cas9 technology together make drug target prediction feasible. However, there is still a large gap between predicted results and actionable targets in real tumors. Biological network models provide great modus to mimic genetic interactions in real biological systems, which can benefit gene perturbation studies and potential target identification for treating PDAC. Nevertheless, building a network model that takes cell-line data and CRISPR-Cas9 data as input to accurately predict potential targets that will respond well on real tissue remains unsolved.

Methods

We developed a novel algorithm ‘Spectral Clustering for Network-based target Ranking’ (SCNrank) that systematically integrates three types of data: expression profiles from tumor tissue, normal tissue and cell-line PDAC; protein-protein interaction network (PPI); and CRISPR-Cas9 data to prioritize potential drug targets for PDAC. The whole algorithm can be classified into three steps: 1. using STRING PPI network skeleton, SCNrank constructs tissue-specific networks with PDAC tumor and normal pancreas tissues from expression profiles; 2. With the same network skeleton, SCNrank constructs cell-line-specific networks using the cell-line PDAC expression profiles and CRISPR-Cas 9 data from pancreatic cancer cell-lines; 3. SCNrank applies a novel spectral clustering approach to reduce data dimension and generate gene clusters that carry common features from both networks. Finally, SCNrank applies a scoring scheme called ‘Target Influence score’ (TI), which estimates a given target’s influence towards the cluster it belongs to, for scoring and ranking each drug target.

Results

We applied SCNrank to analyze 263 expression profiles, CRPSPR-Cas9 data from 22 different pancreatic cancer cell-lines and the STRING protein-protein interaction (PPI) network. With SCNrank, we successfully constructed an integrated tissue PDAC network and an integrated cell-line PDAC network, both of which contain 4414 selected genes that are overexpressed in tumor tissue samples. After clustering, 4414 genes are distributed into 198 clusters, which include 367 targets of FDA approved drugs. These drug targets are all scored and ranked by their TI scores, which we defined to measure their influence towards the network. We validated top-ranked targets in three aspects: Firstly, mapping them onto the existing clinical drug targets of PDAC to measure the concordance. Secondly, we performed enrichment analysis to these drug targets and the clusters there are within, to reveal functional associations between clusters and PDAC; Thirdly, we performed survival analysis for the top-ranked targets to connect targets with clinical outcomes. Survival analysis reveals that overexpression of three top-ranked genes, PGK1, HMMR and POLE2, significantly increases the risk of death in PDAC patients.

Conclusion

SCNrank is an unbiased algorithm that systematically integrates multiple types of omics data to do potential drug target selection and ranking. SCNrank shows great capability in predicting drug targets for PDAC. Pancreatic cancer-associated gene candidates predicted by our SCNrank approach have the potential to guide genetics-based anti-pancreatic drug discovery.

Hyaluronan Mediated Motility Receptor (HMMR) Encodes an Evolutionarily Conserved Homeostasis, Mitosis, and Meiosis Regulator Rather than a Hyaluronan Receptor

Hyaluronan is an extracellular matrix component that absorbs water in tissues and engages cell surface receptors, like Cluster of Differentiation 44 (CD44), to promote cellular growth and movement. Consequently, CD44 demarks stem cells in normal tissues and tumor-initiating cells isolated from neoplastic tissues. Hyaluronan mediated motility receptor (HMMR, also known as RHAMM) is another one of few defined hyaluronan receptors. HMMR is also associated with neoplastic processes and its role in cancer progression is often attributed to hyaluronan-mediated signaling. But, HMMR is an intracellular, microtubule-associated, spindle assembly factor that localizes protein complexes to augment the activities of mitotic kinases, like polo-like kinase 1 and Aurora kinase A, and control dynein and kinesin motor activities. Expression of HMMR is elevated in cells prior to and during mitosis and tissues with detectable HMMR expression tend to be highly proliferative, including neoplastic tissues. Moreover, HMMR is a breast cancer susceptibility gene product. Here, we briefly review the associations between HMMR and tumorigenesis as well as the structure and evolution of HMMR, which identifies Hmmr-like gene products in several insect species that do not produce hyaluronan. This review supports the designation of HMMR as a homeostasis, mitosis, and meiosis regulator, and clarifies how its dysfunction may promote the tumorigenic process and cancer progression.

Hepatitis B Virus X Protein Induces RHAMM-Dependent Motility in Hepatocellular Carcinoma Cells via PI3K-Akt-Oct-1 Signaling

Chronic hepatitis B virus (HBV) infection is a major risk factor for the development of hepatocellular carcinoma (HCC), which represents one of the most common cancers worldwide. Recent studies suggest that HBV's protein X (HBx) plays a crucial role in HCC development and progression. Earlier, genome-wide analysis identified that the receptor for hyaluronan-mediated motility (RHAMM) represents a putative oncogene and is overexpressed in many human cancers, including HCC. However, the mechanism underlying RHAMM upregulation and its role in tumorigenesis remain unclear. Here, we show that ectopic expression of HBx activates the PI3K/Akt/Oct-1 pathway and upregulates RHAMM expression in HCC cells. HBx overexpression leads to dissociation of C/EBPβ from the RHAMM gene promoter, thereby inducing RHAMM upregulation. RHAMM knockdown attenuates HBx-induced cell migration and invasion in vitro. In mice, HBx promotes cancer cell colonization via RHAMM upregulation, resulting in enhanced metastasis. Analysis of gene expression datasets reveals that RHAMM mRNA level is upregulated in patients with HCC with poor prognosis. IMPLICATIONS: These results indicate that RHAMM expression is upregulated by HBx, a process that depends on the inhibition of C/EBPβ activity and activation of the PI3K/Akt/Oct-1 pathway. These results have several implications for the treatment of HBV-positive HCC involving upregulation of RHAMM and cancer metastasis. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/18/3/375/F1.large.jpg.

The Roles of Plant-Derived Triptolide on Non-Small Cell Lung Cancer

Over the past decade, natural compounds have been proven to be effective against many human diseases, including cancers. Triptolide (TPL), a diterpenoid triepoxide from the Chinese herb Tripterygium wilfordii Hook F, has exhibited attractive cytotoxic activity on several cancer cells. An increasing number of studies have emphasized the antitumor effects of TPL on non-small cell lung cancer (NSCLC). Here we mainly focused on the key molecular signaling pathways that lead to the inhibitory effects of TPL on human NSCLC, such as mitogen-activated protein kinases (MAPKs) modulation, inhibition of NF-κB activation, suppression of miRNA expression, etc. In addition, the effect of TIG on immune response in cancer patients is summarized for improved immune modulation utilization. However, the clinical use of TPL is often limited by its severe toxicity and water insolubility. Future clinical trials and drug delivery strategies that will evaluate the security and validate the underlying tumor-killing properties of TPL in human NSCLC are also to be discussed.

Insights into the biology and treatment strategies of pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PNETs) are the second most common primary pancreatic neoplasms after pancreatic ductal adenocarcinoma. PNETs present with widely various clinical manifestation and unfavorable survival rate. The recent advances in next generation sequencing have significantly increased our understanding of the molecular landscape of PNETs and help guide the development of targeted therapies. This review intends to outline a holistic picture of the tumors by discussing current understanding of clinical presentations, up-to-date treatment strategies, novel mouse models, and molecular biology of PNETs. Furthermore, we will provide insight into the future development of more effective targeted therapies that are necessary to manage PNETs.

Function and clinical relevance of RHAMM isoforms in pancreatic tumor progression

The receptor for hyaluronic acid-mediated motility (RHAMM) is upregulated in various cancers. We previously screened genes upregulated in human hepatocellular carcinomas for their metastatic function in a mouse model of pancreatic neuroendocrine tumor (PNET) and identified that human RHAMM^B promoted liver metastasis. It was unknown whether RHAMM^B is upregulated in pancreatic cancer or contributes to its progression. In this study, we found that RHAMM protein was frequently upregulated in human PNETs. We investigated alternative splicing isoforms, RHAMM^A and RHAMM^B, by RNA-Seq analysis of primary PNETs and liver metastases. RHAMM^B, but not RHAMM^A, was significantly upregulated in liver metastases. RHAMM^B was crucial for in vivo metastatic capacity of mouse and human PNETs. RHAMM^A, carrying an extra 15-amino acid-stretch, did not promote metastasis in spontaneous and experimental metastasis mouse models. Moreover, RHAMM^B was substantially higher than RHAMM^A in pancreatic ductal adenocarcinoma (PDAC). RHAMM^B, but not RHAMM^A, correlated with both higher EGFR expression and poorer survival of PDAC patients. Knockdown of EGFR abolished RHAMM^B-driven PNET metastasis. Altogether, our findings suggest a clinically relevant function of RHAMM^B, but not RHAMM^A, in promoting PNET metastasis in part through EGFR signaling. RHAMM^B can thus serve as a prognostic factor for pancreatic cancer.

Impact of the secretome of activated pancreatic stellate cells on growth and differentiation of pancreatic tumour cells

Pancreatic ductal adenocarcinoma (PDAC) exists in a complex desmoplastic microenvironment. As part of it, pancreatic stellate cells (PSCs) provide a fibrotic niche, stimulated by a dynamic communication between activated PSCs and tumour cells. Investigating how PSCs contribute to tumour development and for identifying proteins that the cells secrete during cancer progression, we studied by means of complex antibody microarrays the secretome of activated PSCs. A large number of secretome proteins were associated with cancer-related functions, such as cell apoptosis, cellular growth, proliferation and metastasis. Their effect on tumour cells could be confirmed by growing tumour cells in medium conditioned with activated PSC secretome. Analyses of the tumour cells' proteome and mRNA revealed a strong inhibition of tumour cell apoptosis, but promotion of proliferation and migration. Many cellular proteins that exhibited variations were found to be under the regulatory control of eukaryotic translation initiation factor 4E (eIF4E), whose expression was triggered in tumour cells grown in the secretome of activated PSCs. Inhibition by an eIF4E siRNA blocked the effect, inhibiting tumour cell growth in vitro. Our findings show that activated PSCs acquire a pro-inflammatory phenotype and secret proteins that stimulate pancreatic cancer growth in an eIF4E-dependent manner, providing further insight into the role of stromal cells in pancreatic carcinogenesis and cancer progression.

Alleles of Insm1 determine whether RIP1-Tag2 mice produce insulinomas or nonfunctioning pancreatic neuroendocrine tumors

The two most common types of pancreatic neuroendocrine tumors (PanNETs) are insulinomas and nonfunctioning PanNETs (NF-PanNETs). Insulinomas are small, rarely metastatic tumors that secrete high amounts of insulin, and nonfunctioning PanNETs are larger tumors that are frequently metastatic but that do not secrete hormones. Insulinomas are modeled by the highly studied RIP1-Tag2 (RT2) transgenic mice when bred into a C57Bl/6 (B6) genetic background (also known as RT2 B6 mice). But there has been a need for an animal model of nonfunctioning PanNETs, which in the clinic are a more common and severe disease. Here we show that when bred into a hybrid AB6F1 genetic background, RT2 mice make nonfunctioning PanNETs. Compared to insulinomas produced by RT2 B6 mice, the tumors produced by RT2 AB6F1 mice were larger and more metastatic, and the animals did not suffer from hypoglycemia or hyperinsulinemia. Genetic crosses revealed that a locus in mouse chromosome 2qG1 was linked to liver metastasis and to lack of insulin production. This locus was tightly linked to the gene encoding Insm1, a beta cell transcription factor that was highly expressed in human insulinomas but unexpressed in other types of PanNETs due to promoter hypermethylation. Insm1-deficient human cell lines expressed stem cell markers, were more invasive in vitro, and metastasized at higher rates in vivo when compared to isogenic Insm1-expressing cell lines. These data demonstrate that expression of Insm1 can determine whether a PanNET is a localized insulinoma or a metastatic nonfunctioning tumor.

Orthotopic Pancreatic Tumor Mouse Models of Liver Metastasis

The survival from pancreatic cancer is poor because most patients are diagnosed after the cancer has metastasized. Liver is the most common site of pancreatic cancer metastasis. Orthotopic mouse models of liver metastasis by intrasplenically injecting the pancreatic tumor cells are useful in studying the molecular mechanisms of metastasis and evaluating therapeutic regimens.

Immunohistochemical analysis of RHAMM expression in normal and neoplastic human tissues: a cell cycle protein with distinctive expression in mitotic cells and testicular germ cells

Expression of Receptor for Hyaluronic Acid Mediated Motility (RHAMM) increases cellular motility and RHAMM overexpression promotes invasive phenotype and metastasis of cancer cells. RHAMM has been suggested as a biomarker for poor prognosis in several tumor types, including lung, breast, colorectal, gastric, pancreatic ductal, and ovarian cancers. RNA studies showed restricted RHAMM expression in normal tissues, but its protein expression data in tissues were limited. In light of its potential as a prognostic marker and a therapeutic target, we performed immunohistochemical analysis to systematically characterize RHAMM expression in normal and neoplastic human tissues. Among 29 normal adult tissues, RHAMM protein showed restricted expression and was observed in the thymus, lymph node/tonsil, small intestine, colon, skin, bone marrow, placenta, and testis. The cellular distribution patterns of RHAMM in these normal tissues were consistent with RHAMM being a G2/M cell cycle protein, and this was further supported in comparison to the expression of cyclin B2, another G2/M protein. However, unlike the subcellular localization of cyclin B2, RHAMM decorated mitotic spindles in both anaphase and metaphase. RHAMM expression in tumor tissues is variable; and higher RHAMM protein expression is associated with histologically higher-grade tumors in general. Distinct from its expression in somatic tissues, RHAMM showed diffuse, strong, stage-specific expression in the spermatocyte stage of germ cells in adult testis. The neoplastic counterpart, spermatocytic tumor, also showed strong RHAMM expression. This unique expression in testis suggests that RHAMM may function during normal testicular germ cell maturation.

Triptolide suppresses the in vitro and in vivo growth of lung cancer cells by targeting hyaluronan-CD44/RHAMM signaling

Higher levels of hyaluronan (HA) and its receptors CD44 and RHAMM have been associated with poor prognosis and metastasis in NSCLC. In the current study, our goal was to define, using cellular and orthotopic lung tumor models, the role of HA-CD44/RHAMM signaling in lung carcinogenesis and to assess the potential of triptolide to block HA-CD44/RHAMM signaling and thereby suppress the development and progression of lung cancer. Triptolide reduced the viability of five non-small cell lung cancer (NSCLC) cells, the proliferation and self-renewal of pulmospheres, and levels of HA synthase 2 (HAS2), HAS3, HA, CD44, RHAMM, EGFR, Akt and ERK, but increased the cleavage of caspase 3 and PARP. Silencing of HAS2, CD44 or RHAMM induced similar effects. Addition of excess HA to the culture media completely abrogated the effects of triptolide and siRNAs targeting HAS2, CD44, or RHAMM. In an orthotopic lung cancer model in nude rats, intranasal administration of liposomal triptolide (400 μg/kg) for 8 weeks significantly reduced lung tumor growth as determined by bioluminescence imaging, lung weight measurements and gross and histopathological analysis of tumor burden. Also, triptolide suppressed expressions of Ki-67, a marker for cell proliferation, HAS2, HAS3, HA, CD44, and RHAMM in lung tumors. Overall, our results provide a strong rationale for mitigating lung cancer by targeting the HA-CD44/RHAMM signaling axis.

Screening of biomarkers for liver adenoma in low-dose-rate γ-ray-irradiated mice

PURPOSE

Chronic low-dose-rate (20 mGy/day) γ-irradiation increases the incidence of hepatocellular adenomas (HCA) in female B6C3F1 mice. The purpose of this study is to identify potential serum biomarkers for these HCAs by a new approach.

MATERIAL AND METHODS

Microarray analysis were performed to compare the gene expression profiles of HCAs from mice exposed to low-dose-rate γ-rays with those of normal livers from non-irradiated mice. From the differentially expressed genes, those for possibly secretory proteins were selected. Then, the levels of the proteins in sera were analysed by ELISA.

RESULTS

Microarray analysis identified 4181 genes differentially expressed in HCAs (>2.0-fold). From these genes, those for α-fetoprotein (Afp), α-1B-glycoprotein (A1bg) and serine peptidase inhibitor Kazal type-3 (Spink3) were selected as the genes for candidate proteins. ELISA revealed that the levels of Afp and A1bg proteins in sera significantly increased and decreased, respectively, in low-dose-rate irradiated mice with HCAs and also same tendency was observed in human patients with hepatocellular carcinomas.

CONCLUSION

These results indicate that A1bg could be a new serum biomarker for liver tumor. This new approach of using microarray to select genes for secretory proteins is useful for prediction of novel tumor markers in sera.

Expression of the receptor for hyaluronic acid mediated motility (RHAMM) is associated with poor prognosis and metastasis in non-small cell lung carcinoma

The receptor for hyaluronic acid-mediated motility (RHAMM) is upregulated in various cancers, but its role in primary and metastatic non-small cell lung carcinoma (NSCLC) remains to be determined. Here, we investigate the clinical relevance of RHAMM expression in NSCLC. RHAMM protein expression correlates with histological differentiation stages and extent of the primary tumor (T stages) in 156 patients with primary NSCLC. Importantly, while focal RHAMM staining pattern is present in 57% of primary NSCLC, intense RHAMM protein expression is present in 96% of metastatic NSCLC cases. In a publicly available database, The Cancer Genome Atlas (TCGA), RHAMM mRNA expression is 12- and 10-fold higher in lung adenocarcinoma and squamous lung carcinoma than in matched normal lung tissues, respectively. RHAMM mRNA expression correlates with stages of differentiation and inferior survival in more than 400 cases of lung adenocarcinoma in the Director's Challenge cohort. Of 4 RHAMM splice variants, RHAMMv3 (also known as RHAMMB) is the dominant variant in NSCLC. Moreover, shRNA-mediated knockdown of RHAMM reduced the migratory ability of two lung adenocarcinoma cell lines, H1975 and H3255. Taken together, RHAMM, most likely RHAMMv3 (RHAMMB), can serve as a prognostic factor for lung adenocarcinomas and a potential therapeutic target in NSCLC to inhibit tumor migration.

RHAMM splice variants confer radiosensitivity in human breast cancer cell lines

Biomarkers for prognosis in radiotherapy-treated breast cancer patients are urgently needed and important to stratify patients for adjuvant therapies. Recently, a role of the receptor of hyaluronan-mediated motility (RHAMM) has been suggested for tumor progression. Our aim was (i) to investigate the prognostic value of RHAMM in breast cancer and (ii) to unravel its potential function in the radiosusceptibility of breast cancer cells. We demonstrate that RHAMM mRNA expression in breast cancer biopsies is inversely correlated with tumor grade and overall survival. Radiosusceptibility in vitro was evaluated by sub-G1 analysis (apoptosis) and determination of the proliferation rate. The potential role of RHAMM was addressed by short interfering RNAs against RHAMM and its splice variants. High expression of RHAMMv1/v2 in p53 wild type cells (MCF-7) induced cellular apoptosis in response to ionizing radiation. In comparison, in p53 mutated cells (MDA-MB-231) RHAMMv1/v2 was expressed sparsely resulting in resistance towards irradiation induced apoptosis. Proliferation capacity was not altered by ionizing radiation in both cell lines. Importantly, pharmacological inhibition of the major ligand of RHAMM, hyaluronan, sensitized both cell lines towards radiation induced cell death. Based on the present data, we conclude that the detection of RHAMM splice variants in correlation with the p53 mutation status could help to predict the susceptibility of breast cancer cells to radiotherapy. Additionally, our studies raise the possibility that the response to radiotherapy in selected cohorts may be improved by pharmaceutical strategies against RHAMM and its ligand hyaluronan.

Identification and Characterization of Metastatic Factors by Gene Transfer into the Novel RIP-Tag; RIP-tva Murine Model

Metastatic cancer accounts for 90% of deaths in patients with solid tumors. There is an urgent need to better understand the drivers of cancer metastasis and to identify novel therapeutic targets. To investigate molecular events that drive the progression from primary cancer to metastasis, we have developed a bitransgenic mouse model, RIP-Tag; RIP-tva. In this mouse model, the rat insulin promoter (RIP) drives the expression of the SV40 T antigen (Tag) and the receptor for subgroup A avian leukosis virus (tva) in pancreatic β cells. The mice develop pancreatic neuroendocrine tumors with 100% penetrance through well-defined stages that are similar to human tumorigenesis, with stages including hyperplasia, angiogenesis, adenoma, and invasive carcinoma. Because RIP-Tag; RIP-tva mice do not develop metastatic disease, genetic alterations that promote metastasis can be identified easily. Somatic gene transfer into tva-expressing, proliferating pancreatic β premalignant lesions is achieved through intracardiac injection of avian retroviruses harboring the desired genetic alteration. A titer of >1 x 10⁸ infectious units per ml is considered appropriate for in vivo infection. In addition, avian retroviruses can infect cell lines derived from tumors in RIP-Tag; RIP-tva mice with high efficiency. The cell lines can also be used to characterize the metastatic factors. Here we demonstrate how to utilize this mouse model and cell lines to assess the functions of candidate genes in tumor metastasis.

The hyaluronan-mediated motility receptor RHAMM promotes growth, invasiveness and dissemination of colorectal cancer

In colorectal cancer (CRC), RHAMM is an independent adverse prognostic factor. The aim of the study was therefore to investigate on the role of RHAMM as a potential direct driver of cell proliferation and migration in CRC cell lines and to identify pathways dependent on RHAMM in human CRC.

Proliferation, cell cycle alterations and invasive capacity were tested in two RHAMM- and control- knockdown CRC cell lines by flow cytometry and in vitro assays. Tumorigenicity and metastasis formation was assessed in immunodeficient mice. RNA-Seq and immunohistochemistry was performed on six RHAMM+/- primary CRC tumors.

In vitro, silencing of RHAMM inhibited CRC cell migration and invasion by 50% (p<0.01). In vivo, RHAMM knockdown resulted in slower growth, lower tumor size (p<0.001) and inhibition of metastasis (p<0.001). Patients with RHAMM-high CRC had a worse prognosis (p=0.040) and upregulated pathways for cell cycle progression and adhesion turnover.

RHAMM overexpression is correlated with increased migration and invasion of CRC cells, leads to larger, fast growing tumors, and its downregulation essentially abolishes metastasis in mouse models. RHAMM is therefore a promising therapeutic target in all CRC stages as its inhibition affects growth and dissemination of the primary CRC as well as the metastases.

Redox Responsive Hyaluronic Acid Nanogels for Treating RHAMM (CD168) Over-expressive Cancer, both Primary and Metastatic Tumors

It remains a substantial challenge to targetedly deliver drug to both primary tumors and metastatic lesions employing a single nanoparticle delivery system. Here aiming at the receptor for hyaluronic acid mediated motility (RHAMM or CD168), a specific receptor for hyaluronic acid (HA), the bioreductive responsive HA nanogels loaded doxorubicin were prepared. The targeting effects of HA nanogels in high RHAMM-expressed cancer cells, primary and metastatic tumors were investigated. It was found that HA nanogels show a strong in vitro and in vivo RHAMM-mediated cellular uptake and drug delivery. The cellular uptake of HA nanogels in high RHAMM-expressed LNCaP and H22 cells was far more than the uptake in low RHAMM-expressed NIH3T3 cells. The IC50 value of drug-loaded HA nanogels against H22 cells was lower than that of free drug. In vivo antitumor activity examinations showed that the HA nanogels not only had significantly superior antitumor efficacy in murine H22 and human LNCaP tumor-bearing mice but also exhibited much deep tumor penetration. The drug delivery of lymph node metastasis by systemically administering HA nanogels demonstrated that the HA nanogels could sufficiently increase drug concentration in metastatic lymph node by RHAMM-HA interaction and inhibit the growth of metastatic lymph node, even completely heal malignant lymph node metastasis. Thus, RHAMM-directed drug delivery is a promising therapy route for treating both primary and metastatic tumors.

For robust big data analyses: a collection of 150 important pro-metastatic genes

Metastasis is the greatest contributor to cancer-related death. In the era of precision medicine, it is essential to predict and to prevent the spread of cancer cells to significantly improve patient survival. Thanks to the application of a variety of high-throughput technologies, accumulating big data enables researchers and clinicians to identify aggressive tumors as well as patients with a high risk of cancer metastasis. However, there have been few large-scale gene collection studies to enable metastasis-related analyses. In the last several years, emerging efforts have identified pro-metastatic genes in a variety of cancers, providing us the ability to generate a pro-metastatic gene cluster for big data analyses. We carefully selected 285 genes with in vivo evidence of promoting metastasis reported in the literature. These genes have been investigated in different tumor types. We used two datasets downloaded from The Cancer Genome Atlas database, specifically, datasets of clear cell renal cell carcinoma and hepatocellular carcinoma, for validation tests, and excluded any genes for which elevated expression level correlated with longer overall survival in any of the datasets. Ultimately, 150 pro-metastatic genes remained in our analyses. We believe this collection of pro-metastatic genes will be helpful for big data analyses, and eventually will accelerate anti-metastasis research and clinical intervention.

Methods to Study Metastasis in Genetically Modified Mice

Metastasis is often modeled by xenotransplantation of cell lines in immunodeficient mice. A wealth of information about tumor cell behavior in the new environment is obtained from these efforts. Yet by design, this approach is "tumor-centric," as it focuses on cell-autonomous determinants of human tumor dissemination in mouse tissues, in effect using the animal body as a sophisticated "Petri dish" providing nutrients and support for tumor growth. Transgenic or gene knockout mouse models of cancer allow the study of tumor spread as a systemic disease and offer a complimentary approach for studying the natural history of cancer. This introduction is aimed at describing the overall methodological approach to studying metastasis in genetically modified mice, with a particular focus on using animals with regulated expression of potent human oncogenes in the breast.

Bcl-xL promotes metastasis independent of its anti-apoptotic activity

Bcl-xL suppresses mitochondria-mediated apoptosis and is frequently overexpressed in cancer to promote cancer cell survival. Bcl-xL also promotes metastasis. However, it is unclear whether this metastatic function is dependent on its anti-apoptotic activity in the mitochondria. Here we demonstrate that Bcl-xL promotes metastasis independent of its anti-apoptotic activity. We show that apoptosis-defective Bcl-xL mutants and an engineered Bcl-xL targeted to the nucleus promote epithelial–mesenchymal transition, migration, invasion and stemness in pancreatic neuroendocrine tumour (panNET) and breast cancer cell lines. However, Bcl-xL proteins targeted to the mitochondria or outside of the nucleus do not have these functions. We confirm our findings in spontaneous and xenograft mouse models. Furthermore, Bcl-xL exerts metastatic function through epigenetic modification of the TGFβ promoter to increase TGFβ signalling. Consistent with these findings, we detect nuclear Bcl-xL in human metastatic panNETs. Taken together, the metastatic function of Bcl-xL is independent of its anti-apoptotic activity and its residence in the mitochondria.

Bcl-xL is an anti-apoptotic protein that has also been implicated in metastasis. In this study, the authors show that nuclear Bcl-xL promotes metastasis by regulating TGFβ signaling, which is independent of the anti-apoptotic activity of Bcl-xL.

PP2B and ERK1/2 regulate hyaluronan synthesis of HT168 and WM35 human melanoma cell lines

Hyaluronan (HA) is the major glycosaminoglycan component of the extracellular matrix in either normal or malignant tissues and it may affect proliferation, motility and differentiation of various cell types. Three isoforms of plasma membrane-bound hyaluronan synthases (HAS 1, 2 and 3) secrete and simultaneously bind pericellular HA. HAS enzymes are subjects of post-translational protein phosphorylation which is believed to regulate their enzymatic activity. In this study, we investigated the HA homeostasis of normal human epidermal melanocytes, HT168 and WM35 human melanoma cell lines and melanoma metastases. HAS2 and HAS3 were detected in all the samples, while the expression of HAS1 was not detectable in any case. Malignant tissue samples and melanoma cell lines contained extra- and intracellular HA abundantly but not normal melanocytes. Applying HA as a chemoattractant facilitated the migration of melanoma cells in Boyden chamber. The amount of HA was reduced upon the inhibition of calcineurin with cyclosporine A (CsA), while the inhibition of ERK1/2 with PD098059 elevated it in both cell lines. The signals of Ser/Thr phosphoproteins at 57 kD were stronger after CsA treatment, while a markedly weaker signal was detected upon inhibition of the MAPK pathway. Our results suggest opposing effects of the two investigated enzymes on the HA homeostasis of melanoma cells. We propose that the dephosphorylation of HAS enzymes targeted by PP2B augments HA production, while their phosphorylation by the activity of MAPK pathway reduces HA synthesis. As the expression of the HA receptor RHAMM was also significantly enhanced by PD098059, the MAPK pathway exerted a complex attenuating effect on HA signalling in the investigated melanoma cells. This observation suggests that the application of MAPK-ERK pathway inhibitors requires a careful therapeutic design in melanoma treatment.

Identification, design and synthesis of tubulin-derived peptides as novel hyaluronan mimetic ligands for the receptor for hyaluronan-mediated motility (RHAMM/HMMR)

Fragments of the extracellular matrix component hyaluronan (HA) promote tissue inflammation, fibrosis and tumor progression. HA fragments act through HA receptors including CD44, LYVE1, TLR2, 4 and the receptor for hyaluronan mediated motility (RHAMM/HMMR). RHAMM is a multifunctional protein with both intracellular and extracellular roles in cell motility and proliferation. Extracellular RHAMM binds directly to HA fragments while intracellular RHAMM binds directly to ERK1 and tubulin. Both HA and regions of tubulin (s-tubulin) are anionic and bind to basic amino acid-rich regions in partner proteins, such as in HA and tubulin binding regions of RHAMM. We used this as a rationale for developing bioinformatics and SPR (surface plasmon resonance) based screening to identify high affinity anionic RHAMM peptide ligands. A library of 12-mer peptides was prepared based on the carboxyl terminal tail sequence of s-tubulin isoforms and assayed for their ability to bind to the HA/tubulin binding region of recombinant RHAMM using SPR. This approach resulted in the isolation of three 12-mer peptides with nanomolar affinity for RHAMM. These peptides bound selectively to RHAMM but not to CD44 or TLR2,4 and blocked RHAMM:HA interactions. Furthermore, fluorescein-peptide uptake by PC3MLN4 prostate cancer cells was blocked by RHAMM mAb but not by CD44 mAb. These peptides also reduced the ability of prostate cancer cells to degrade collagen type I. The selectivity of these novel HA peptide mimics for RHAMM suggest their potential for development as HA mimetic imaging and therapeutic agents for HA-promoted disease.

Interactions between Hyaluronan and Its Receptors (CD44, RHAMM) Regulate the Activities of Inflammation and Cancer

The glycosaminoglycan hyaluronan (HA), a major component of extracellular matrices, and cell surface receptors of HA have been proposed to have pivotal roles in cell proliferation, migration, and invasion, which are necessary for inflammation and cancer progression. CD44 and receptor for HA-mediated motility (RHAMM) are the two main HA-receptors whose biological functions in human and murine inflammations and tumor cells have been investigated comprehensively. HA was initially considered to be only an inert component of connective tissues, but is now known as a “dynamic” molecule with a constant turnover in many tissues through rapid metabolism that involves HA molecules of various sizes: high molecular weight HA (HMW HA), low molecular weight HA, and oligosaccharides. The intracellular signaling pathways initiated by HA interactions with CD44 and RHAMM that lead to inflammatory and tumorigenic responses are complex. Interestingly, these molecules have dual functions in inflammations and tumorigenesis. For example, the presence of CD44 is involved in initiation of arthritis, while the absence of CD44 by genetic deletion in an arthritis mouse model increases rather than decreases disease severity. Similar dual functions of CD44 exist in initiation and progression of cancer. RHAMM overexpression is most commonly linked to cancer progression, whereas loss of RHAMM is associated with malignant peripheral nerve sheath tumor growth. HA may similarly perform dual functions. An abundance of HMW HA can promote malignant cell proliferation and development of cancer, whereas antagonists to HA-CD44 signaling inhibit tumor cell growth in vitro and in vivo by interfering with HMW HA-CD44 interaction. This review describes the roles of HA interactions with CD44 and RHAMM in inflammatory responses and tumor development/progression, and how therapeutic strategies that block these key inflammatory/tumorigenic processes may be developed in rodent and human diseases.

Hyaluronan and RHAMM in wound repair and the "cancerization" of stromal tissues

Tumors and wounds share many similarities including loss of tissue architecture, cell polarity and cell differentiation, aberrant extracellular matrix (ECM) remodeling (Ballard et al., 2006) increased inflammation, angiogenesis, and elevated cell migration and proliferation. Whereas these changes are transient in repairing wounds, tumors do not regain tissue architecture but rather their continued progression is fueled in part by loss of normal tissue structure. As a result tumors are often described as wounds that do not heal. The ECM component hyaluronan (HA) and its receptor RHAMM have both been implicated in wound repair and tumor progression. This review highlights the similarities and differences in their roles during these processes and proposes that RHAMM-regulated wound repair functions may contribute to “cancerization” of the tumor microenvironment.

Stromal reengineering to treat pancreas cancer

Pancreatic ductal adenocarcinoma co-opts multiple cellular and extracellular mechanisms to create a complex cancer organ with an unusual proclivity for metastasis and resistance to therapy. Cell-autonomous events are essential for the initiation and maintenance of pancreatic ductal adenocarcinoma, but recent studies have implicated critical non-cell autonomous processes within the robust desmoplastic stroma that promote disease pathogenesis and resistance. Thus, non-malignant cells and associated factors are culprits in tumor growth, immunosuppression and invasion. However, even this increasing awareness of non-cell autonomous contributions to disease progression is tempered by the conflicting roles stromal elements can play. A greater understanding of stromal complexity and complicity has been aided in part by studies in highly faithful genetically engineered mouse models of pancreatic ductal adenocarcinoma. Insights gleaned from such studies are spurring the development of therapies designed to reengineer the pancreas cancer stroma and render it permissive to agents targeting cell-autonomous events or to reinstate immunosurveillance. Integrating conventional and immunological treatments in the context of stromal targeting may provide the key to a durable clinical impact on this formidable disease.

Interplay of mevalonate and Hippo pathways regulates RHAMM transcription via YAP to modulate breast cancer cell motility

Expression of receptor for hyaluronan-mediated motility (RHAMM), a breast cancer susceptibility gene, is tightly controlled in normal tissues but elevated in many tumors, contributing to tumorigenesis and metastases. However, how the expression of RHAMM is regulated remains elusive. Statins, inhibitors of mevalonate metabolic pathway widely used for hypercholesterolemia, have been found to also have antitumor effects, but little is known of the specific targets and mechanisms. Moreover, Hippo signaling pathway plays crucial roles in organ size control and cancer development, yet its downstream transcriptional targets remain obscure. Here we show that RHAMM expression is regulated by mevalonate and Hippo pathways converging onto Yes-associated protein (YAP)/TEAD, which binds RHAMM promoter at specific sites and controls its transcription and consequently breast cancer cell migration and invasion (BCCMI); and that simvastatin inhibits BCCMI via targeting YAP-mediated RHAMM transcription. Required for ERK phosphorylation and BCCMI, YAP-activated RHAMM transcription is dependent on mevalonate and sensitive to simvastatin, which modulate RHAMM transcription by modulating YAP phosphorylation and nuclear-cytoplasmic localization. Further, modulation by mevalonate/simvastatin of YAP-activated RHAMM transcription requires geranylgeranylation, Rho GTPase activation, and actin cytoskeleton rearrangement, but is largely independent of MST and LATS kinase activity. These findings from in vitro and in vivo investigations link mevalonate and Hippo pathways with RHAMM as a downstream effector, a YAP-transcription and simvastatin-inhibition target, and a cancer metastasis mediator; uncover a mechanism regulating RHAMM expression and cancer metastases; and reveal a mode whereby simvastatin exerts anticancer effects; providing potential targets for cancer therapeutic agents.

SALL4 is a new target in endometrial cancer

Aggressive cancers and embryonic stem (ES) cells share a common gene expression signature. Identifying the key factors/pathway(s) within this ES signature responsible for the aggressiveness of cancers can lead to a potential cure. In this study, we find that SALL4, a gene involved in the maintenance of ES cell self-renewal, is aberrantly expressed in 47.7% of primary human endometrial cancer samples. It is not expressed in normal or hyperplastic endometrial. More importantly, SALL4 expression is positively correlated with worse patient survival and aggressive features such as metastasis in endometrial carcinoma. Further functional studies have shown that loss of SALL4 inhibits endometrial cancer cell growth in vitro and tumorigenicity in vivo, as a result of inhibition of cell proliferation and increased apoptosis. In addition, down-regulation of SALL4 significantly impedes the migration and invasion properties of endometrial cancer cells in vitro and their metastatic potential in vivo. Furthermore, manipulation of SALL4 expression can affect drug sensitivity of endometrial cancer cells to carboplatin. Moreover, we show that SALL4 specifically binds to the c-Myc promoter region in endometrial cancer cells. While down-regulation of SALL4 leads to a decreased expression of c-Myc at both protein and mRNA levels, ectopic SALL4 overexpression causes increased c-Myc protein and mRNA expression, indicating that c-Myc is one of the SALL4 downstream targets in endometrial tumorigenesis. In summary, we are the first to demonstrate that SALL4 plays functional role(s) in metastasis and drug resistance in aggressive endometrial cancer. As a consequence of its functional roles in cancer cell and absence in normal tissue, SALL4 is a potential novel therapeutic target for the high risk endometrial cancer patient population.

Met synergizes with p53 loss to induce mammary tumors that possess features of claudin-low breast cancer

Triple-negative breast cancer (TNBC) accounts for ∼20% of cases and contributes to basal and claudin-low molecular subclasses of the disease. TNBCs have poor prognosis, display frequent mutations in tumor suppressor gene p53 (TP53), and lack targeted therapies. The MET receptor tyrosine kinase is elevated in TNBC and transgenic Met models (Met(mt)) develop basal-like tumors. To investigate collaborating events in the genesis of TNBC, we generated Met(mt) mice with conditional loss of murine p53 (Trp53) in mammary epithelia. Somatic Trp53 loss, in combination with Met(mt), significantly increased tumor penetrance over Met(mt) or Trp53 loss alone. Unlike Met(mt) tumors, which are histologically diverse and enriched in a basal-like molecular signature, the majority of Met(mt) tumors with Trp53 loss displayed a spindloid pathology with a distinct molecular signature that resembles the human claudin-low subtype of TNBC, including diminished claudins, an epithelial-to-mesenchymal transition signature, and decreased expression of the microRNA-200 family. Moreover, although mammary specific loss of Trp53 promotes tumors with diverse pathologies, those with spindloid pathology and claudin-low signature display genomic Met amplification. In both models, MET activity is required for maintenance of the claudin-low morphological phenotype, in which MET inhibitors restore cell-cell junctions, rescue claudin 1 expression, and abrogate growth and dissemination of cells in vivo. Among human breast cancers, elevated levels of MET and stabilized TP53, indicative of mutation, correlate with highly proliferative TNBCs of poor outcome. This work shows synergy between MET and TP53 loss for claudin-low breast cancer, identifies a restricted claudin-low gene signature, and provides a rationale for anti-MET therapies in TNBC.