Introduction
Hyaluronic acid (HA), or hyaluronan, is a naturally occurring polysaccharide found ubiquitously throughout the human body, particularly in connective tissues, skin, and synovial fluid. It plays a crucial role in maintaining the extracellular matrix's structural integrity and in various cellular processes, including cell proliferation, migration, and differentiation. HA is involved in wound healing, tissue repair, and inflammation regulation, demonstrating its essential role in normal physiological functions. However, growing evidence suggests that HA can also contribute to the progression and metastasis of certain types of cancer, making it a molecule of interest in oncology research.
What Is the Role of Hyaluronic Acid in Promoting Cancer Cell Growth?
Hyaluronic acid (HA) aids in cancer cell growth primarily by fostering a conducive environment that enables tumor cells to multiply and infiltrate adjacent tissues. As a fundamental element of the extracellular matrix, hyaluronic acid interacts with specific cell surface receptors, including cluster of differentiation 44 (CD44) and receptor for hyaluronan-mediated motility (RHAMM), triggering signaling pathways that encourage cell proliferation, survival, and migration.
The attachment of hyaluronic acid to CD44 activates essential pathways like phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) and Rat Sarcoma virus/Mitogen-Activated Protein Kinase (Ras/MAPK), which are vital for sustaining cell life and encouraging cell division. In cancerous cells, these pathways are frequently hyperactivated, amplifying the cells' capacity for uncontrolled growth. Furthermore, the interaction between hyaluronic acid and CD44 can activate the sarcoma (Src) family of kinases, which enhance cancer cell invasion and metastasis through modifications to the cytoskeleton and changes in cell adhesion characteristics.
Additionally, hyaluronic acid indirectly supports cancer cell growth by inducing the secretion of factors that promote angiogenesis, such as vascular endothelial growth factor (VEGF—a protein that stimulates the formation of blood vessels). This protein facilitates the creation of new blood vessels necessary for tumor sustenance. Angiogenesis is crucial for tumors' ongoing development and survival, providing them with the required nutrients and oxygen supply.
How Do Hyaluronic Acid Synthases and Hyaluronidases Contribute to Cancer?
Balancing the amount of hyaluronic acid (HA) within the immediate vicinity of a tumor is essential for understanding how cancer progresses. The production of hyaluronic acid is governed by a set of enzymes called hyaluronic acid synthases (including HAS1, HAS2, and HAS3), while its decomposition is managed by hyaluronidases (encompassing HYAL1, HYAL2, and HYAL3).
Significant research has indicated that boosting the activity of hyaluronic acid synthases, particularly hyaluronic acid synthase 2 (HAS2) and hyaluronic acid synthase 3 (HAS3), often leads to an increase in hyaluronic acid production. This rise in hyaluronic acid levels helps support the growth and spread of cancer cells by offering a supportive structure that enhances tumor cell adherence and movement. Conversely, an increase in hyaluronidases, such as hyaluronidase 1 (HYAL1), is linked to lower hyaluronic acid levels, resulting in less aggressive tumor growth and invasion. This highlights the complex role hyaluronic acid plays in the progression of cancer.
An increase in the activity of hyaluronic acid synthase 2 (HAS2) and hyaluronic acid synthase 3 (HAS3) in cancer cells increases hyaluronic acid production. This enhancement encourages cancer cell proliferation, migration, and invasion by improving the cells' interaction with their surrounding environment. On the other hand, an overabundance of hyaluronidase 1 (HYAL1) in cancer cells decreases hyaluronic acid levels, which can limit tumor growth and invasion but may also make it easier for cancer cells to spread by breaking down barriers to their dispersion.
How Does Hyaluronic Acid Contribute to Tumor Angiogenesis and Metastasis?
Besides its direct impacts on cancer cell growth and longevity, hyaluronic acid (HA) significantly influences angiogenesis and metastasis, which are vital for tumor expansion and dissemination.
HA can induce the release of pro-angiogenic substances, including vascular endothelial growth factor (VEGF), which encourages the development of new blood vessels inside the tumor.
This augmented blood supply delivers essential nutrients and oxygen to the tumor, aiding its growth. It also facilitates the circulation of cancer cells into the bloodstream, thus enabling metastasis. Cancer cells' capability to metastasize is a significant determinant in cancer-related deaths due to its role in spreading the disease to remote parts of the body.
Moreover, the interaction between hyaluronic acid and cluster of differentiation 44 (CD44) has been observed to trigger various signaling pathways that augment cancer cells' mobility and invasive tendencies. This allows them to penetrate the basement membrane and infiltrate neighboring tissues. This phase is pivotal in the metastatic sequence, permitting cancer cells to migrate to distant locations within the body and advance the disease's progression.
How Can Hyaluronic Acid Be Targeted for Cancer Therapy?
Considering the significant role of hyaluronic acid (HA) in advancing cancer, various therapeutic methodologies have been crafted to focus on HA-induced signaling and its interconnected pathways. One strategy involves preventing the production of hyaluronic acid by employing specific inhibitors against the hyaluronic acid synthases. Another approach seeks to sever the bond between hyaluronic acid and its cell surface receptors, such as cluster of differentiation 44 (CD44) and receptor for hyaluronan-mediated motility (RHAMM), using monoclonal antibodies or small molecules that obstruct these connections.
Furthermore, the exploration of administering hyaluronidase enzymes is underway to dismantle the HA-laden extracellular matrix, thereby increasing the accessibility of anticancer medications within tumors. These targeted therapeutic methods have demonstrated positive outcomes in early-stage investigations and are presently undergoing clinical assessments to devise more efficacious cancer treatments.
By focusing on the HA pathway, these treatments aim to mitigate tumor expansion and metastasis while augmenting the potency of traditional therapies. This research domain offers prospects for pioneering drug discoveries, potentially leading to individualized cancer treatment regimens that utilize HA's unique attributes.
Conclusion
The available evidence demonstrates the critical role of hyaluronic acid in promoting cancer cell growth, angiogenesis, and metastasis. The upregulation of hyaluronic acid synthesis and the interaction between hyaluronic acid and its cell surface receptors activate various signaling pathways that support cancer cells' proliferation, survival, and invasive behavior.
As a result, the therapeutic targeting of hyaluronic acid and its associated pathways has emerged as a promising strategy for treating various types of cancer. Ongoing research in this field is expected to yield new insights and lead to the development of more effective cancer therapies in the future.
By understanding and manipulating the role of hyaluronic acid in cancer, researchers and clinicians aim to develop targeted therapies that can inhibit tumor growth and improve patient outcomes. Continuous advancements in understanding hyaluronic acid's biology may also provide broader insights into tumor microenvironment interactions, potentially unveiling new biomarkers for early cancer detection and progression monitoring.
