Key Role of Hyaluronan Metabolism for the Development of Brain Metastases in Triple-Negative Breast Cancer

Clinicopathological significance of hyaluronan and hyaluronidase 2 (HYAL2) in breast cancer

Hyaluronan (HA), as a component of extracellular matrix, has pivotal roles in both physiological and pathological condition. In breast cancer, while high molecular weight HA is produced by hyaluronan synthase, it is degraded by hyaluronidases (hyaluronidase-1 (HYAL1) and hyaluronidase-2 (HYAL2)) into low molecular weight HA (LMW HA), which is considered to have pro-tumorigenic effects in human malignancies. However, HA and HYAL2, the rate-limiting enzyme of HA degradation, have not been comprehensively examined in breast cancer and clinicopathological significance of LMW HA remains to be elucidated in breast cancer. We therefore histochemically localized HA as well as HYAL2 in 116 breast cancer tissues. In addition, we examined size-dependent function of HA on breast cancer cell proliferation and migration using MCF-7 and MDA-MB-231 breast cancer cell lines. HA was localized in both the stroma and breast carcinoma cells, while HYAL2 was predominantly localized in breast carcinoma cells. HA was significantly correlated with cell proliferation and invasion ability as well as increased risk of recurrence especially in HYAL2 positive group. On the other hand, HYAL2 was correlated with breast cancer cell proliferation and increased risk of recurrence. In addition, in vitro analyses revealed that lower molecular weight HA increased sphere forming ability and migration in MCF-7 and MDA-MB-231, whereas higher molecular weight HA inhibited them. It was concluded that HA needs to be degraded by HYAL2 to exert pro-tumorigenic effects and comprehensive HA/HYAL2 status serves as a potent prognostic factor in breast cancer.

Hyaluronic acid as a tumor progression agent and a potential chemotherapeutic biomolecule against cancer: A review on its dual role

Hyaluronic acid is a major constituent of the extracellular matrix of vertebrate tissue that provides mechanical support to cells and acts as a mediator in regulation of necessary biochemical process essential for maintenance of tissue homeostasis. The variation in quantity of hyaluronic acid content in tissues is often associated with different pathological conditions. It is associated with tumor aggression and progression as it plays crucial role in regulating different aspects of tumorigenesis and several defined hallmarks of cancer. It assists in tumor progression by undergoing extracellular remodeling to establish tumor microenvironment which restricts the delivery of cytotoxic drugs to neoplastic cells due to increase in interstitial pressure. Hyaluronic acid catabolic and anabolic genes and low-molecular weight hyaluronic acid play significant role in the establishing tumor microenvironment by assisting in cell proliferation, metastasis and invasion. On the other hand, it is also used as an effective drug-delivery platform in cancer therapies as its biocompatibility and biodegradability lower the toxicity of chemotherapeutic drugs and increase drug retention. High-molecular weight hyaluronic acid-bioconjugates specifically bind with hyaladherins, facilitating targeted drug delivery and also exert anti-inflammatory properties. This review also highlights the market and patent trends in the development of effective chemotherapeutic hyaluronic acid formulations and the current scenario regarding clinical trials.

DNA Methylation Status of HYAL1 in Malignant and Benign Thyroid Nodules

Differentiation between benign and malignant thyroid nodules has been a challenge in clinical practice. Exploring a novel biomarker to determine the malignancy of thyroid nodules has important implications. We semi-quantitatively determined the DNA methylation levels of four CpG sites located at the gene body of HYAL1 in formalin-fixed paraffin-embedded (FFPE) tissue samples from 190 early-stage papillary thyroid cancer (PTC) cases and 190 age- and gender-matched subjects with benign thyroid nodule (BTN). HYAL1 expression was evaluated by immunohistochemical (IHC) staining in another cohort of 55 PTC and 55 matched BTN cases. Covariates-adjusted odds ratios (ORs) for 10% increased methylation were calculated by binary logistic regression. A 165 bp amplicon covering four CpG sites at the second exon of HYAL1 gene was designed. After adjusted for all covariates, higher methylation level of HYAL1_CpG_3,4 in the FFPE tissue was associated with PTC (OR per 10% increased methylation=1.53, p=0.025), even with stage І PTC (OR per 10% increased methylation=1.58, p=0.021). Hypermethylation of HYAL1_CpG_3,4 had a significant association with early-stage PTC in the females (OR per 10% increased methylation=1.60, p=0.028) rather than in the males. Besides, we found the higher expression of HYAL1 protein in PTC than that in BTN patients (IHC score: 2.3 vs. 0.5, p=1.00E-06). Our study suggested altered methylation and expression of HYAL1 could be a novel and potential biomarker in distinguishing malignant and benign thyroid nodules.

Critical functions of extracellular matrix in brain metastasis seeding

Human brain is characterized by extremely sparse extracellular matrix (ECM). Despite its low abundance, the significance of brain ECM in both physiological and pathological conditions should not be underestimated. Brain metastasis is a serious complication of cancer, and recent findings highlighted the contribution of ECM in brain metastasis development. In this review, we provide a comprehensive outlook on how ECM proteins promote brain metastasis seeding. In particular, we discuss (1) disruption of the blood-brain barrier in brain metastasis; (2) role of ECM in modulating brain metastasis dormancy; (3) regulation of brain metastasis seeding by ECM-activated integrin signaling; (4) functions of brain-specific ECM protein reelin in brain metastasis. Lastly, we consider the possibility of targeting ECM for brain metastasis management.

Targeting BET Proteins Decreases Hyaluronidase-1 in Pancreatic Cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is characterized by the presence of dense stroma that is enriched in hyaluronan (HA), with increased HA levels associated with more aggressive disease. Increased levels of the HA-degrading enzymes hyaluronidases (HYALs) are also associated with tumor progression. In this study, we evaluate the regulation of HYALs in PDAC.

METHODS

Using siRNA and small molecule inhibitors, we evaluated the regulation of HYALs using quantitative real-time PCR (qRT-PCR), Western blot analysis, and ELISA. The binding of BRD2 protein on the HYAL1 promoter was evaluated by chromatin immunoprecipitation (ChIP) assay. Proliferation was evaluated by WST-1 assay. Mice with xenograft tumors were treated with BET inhibitors. The expression of HYALs in tumors was analyzed by immunohistochemistry and by qRT-PCR.

RESULTS

We show that HYAL1, HYAL2, and HYAL3 are expressed in PDAC tumors and in PDAC and pancreatic stellate cell lines. We demonstrate that inhibitors targeting bromodomain and extra-terminal domain (BET) proteins, which are readers of histone acetylation marks, primarily decrease HYAL1 expression. We show that the BET family protein BRD2 regulates HYAL1 expression by binding to its promoter region and that HYAL1 downregulation decreases proliferation and enhances apoptosis of PDAC and stellate cell lines. Notably, BET inhibitors decrease the levels of HYAL1 expression in vivo without affecting the levels of HYAL2 or HYAL3.

CONCLUSIONS

Our results demonstrate the pro-tumorigenic role of HYAL1 and identify the role of BRD2 in the regulation of HYAL1 in PDAC. Overall, these data enhance our understanding of the role and regulation of HYAL1 and provide the rationale for targeting HYAL1 in PDAC.

Insights into the Molecular Mechanisms Mediating Extravasation in Brain Metastasis of Breast Cancer, Melanoma, and Lung Cancer

Brain metastasis is an incurable end-stage of systemic cancer associated with poor prognosis, and its incidence is increasing. Brain metastasis occurs through a multi-step cascade where cancer cells spread from the primary tumor site to the brain. The extravasation of tumor cells through the blood-brain barrier (BBB) is a critical step in brain metastasis. During extravasation, circulating cancer cells roll along the brain endothelium (BE), adhere to it, then induce alterations in the endothelial barrier to transmigrate through the BBB and enter the brain. Rolling and adhesion are generally mediated by selectins and adhesion molecules induced by inflammatory mediators, while alterations in the endothelial barrier are mediated by proteolytic enzymes, including matrix metalloproteinase, and the transmigration step mediated by factors, including chemokines. However, the molecular mechanisms mediating extravasation are not yet fully understood. A better understanding of these mechanisms is essential as it may serve as the basis for the development of therapeutic strategies for the prevention or treatment of brain metastases. In this review, we summarize the molecular events that occur during the extravasation of cancer cells through the blood-brain barrier in three types of cancer most likely to develop brain metastasis: breast cancer, melanoma, and lung cancer. Common molecular mechanisms driving extravasation in these different tumors are discussed.