C1q-HA Matrix Regulates the Local Synthesis of Hyaluronan in Malignant Pleural Mesothelioma by Modulating HAS3 Expression

Our plain-English summary of C1q-HA Matrix Regulates the Local Synthesis of Hyaluronan in Malignant Pleural Mesothelioma by Modulating HAS3 Expression, by R. Vidergar, A. Balduit, P. Zacchi, et al (Cancers, 2021).

The study

• Authors: R. Vidergar, A. Balduit, P. Zacchi, C. Agostinis, A. Mangogna, B. Belmonte, M. Grandolfo, F. Salton, M. Biolo, F. Zanconati, M. Confalonieri, R. Bulla
• Journal: Cancers
• Published: 2021;13(3)
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Increased hyaluronic acid (HA) production is often associated with cancer progression. In malignant pleural mesothelioma (MPM), HA is found at elevated levels in pleural effusions and sera of patients, and it has been widely debated whether MPM cells are able to produce HA by themselves or through the release of growth factors stimulating other cells. Another key component of the MPM microenvironment is C1q, which can act as a pro-tumorigenic factor favoring cell adhesion, migration and proliferation. The aim of the current study was to prove that MPM primary cells are able to synthesize HA and to inquire the stimulus given by C1q-HA matrix to HA synthesis. We confirmed the presence of a HA coat and cable-like structures around MPM primary cells, as well as an intracellular pool, mainly localized in the cytoplasmic and perinuclear region. After evaluating HA synthase (HAS) enzymes' basal expression in MPM primary cells, we found that C1q bound to HA was able to impinge upon HA homeostasis by upregulating HAS3 both at the mRNA and the protein levels. High expression of HAS3 has been correlated with a shorter life expectancy in MPM by bioinformatical analysis. These data confirmed that C1q bound to HA may exert pro-tumorigenic activity and identified HAS3 as a potential target in MPM.

In plain English

This was a laboratory study of malignant pleural mesothelioma (MPM) cells taken from pleural biopsies of patients in Trieste, Italy, who had reported asbestos exposure. The article describes eight male patients with the epithelioid type. The study did not measure asbestos exposure. The authors asked whether the tumor cells make hyaluronic acid (HA), a substance found at high levels in MPM, and whether a matrix of HA bound to the immune protein C1q changes this. Staining showed HA in the tumor stroma, an HA coat and cable-like strands around the patients' cells, and HA inside the cells, mostly in the cytoplasm and around the nucleus. A normal mesothelial cell line, Met5A, showed no such staining or coat. Cells grown on the C1q–HA matrix had higher levels of the HA-making enzyme HAS3 than cells on HA alone (p less than 0.05), at both gene and protein level. HAS1 and HAS2 showed no significant change. In a public mesothelioma dataset (TCGA), high HAS3 expression was linked to lower survival (p less than 0.01). The authors concluded that MPM cells make HA themselves and that HAS3 is a potential target.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory (in vitro) study of primary tumor cells and tissue sections from patients, with a bioinformatic survival analysis of a public dataset
• Who was studied: Pleural biopsy tissue and primary MPM cells from patients at the University Hospital of Cattinara, Trieste, Italy. The article describes eight patients: all male, Caucasian, epithelioid type, none treated with chemotherapy or radiotherapy before sampling, mean age at diagnosis 76.4 plus or minus 5.1 years. Comparison cell lines were Met5A (non-malignant mesothelial) and NCI-H28 (mesothelioma). Survival data came from The Cancer Genome Atlas Mesothelioma (TCGA-MESO) dataset.
• Exposure: Asbestos exposure was a reported feature of the patients biopsied, but it was not measured or analysed, and no fiber types are given. The laboratory treatments studied were high-molecular-weight HA (1.5 MDa, 50 µg/mL) immobilized as a matrix, with or without C1q (25 µg/mL).
• Main results:
  • In MPM tissue sections, Alcian blue staining showed strong HA positivity, especially in the tumor-associated stroma.
  • MPM primary cells showed an HA coat that excluded red blood cells. The coat was absent in normal Met5A mesothelial cells and in MPM cells treated with hyaluronidase.
  • Inside MPM primary cells, HA appeared as vesicular or globular structures spread through the cell and concentrated around the nucleus.
  • HA only partly overlapped with markers of cell compartments (calnexin and Rab11A). The authors interpreted this as HA being mainly in the cytoplasm.
  • At the gene (mRNA) level, HAS1 and HAS2 were the main HA synthase enzymes in all eight MPM primary cell populations, and HAS3 was very low.
  • At the protein level, MPM primary cells stained positive for all three HAS enzymes. The NCI-H28 mesothelioma cell line showed a similar pattern.
  • In MPM tissue, C1q was found in the tumor stroma, in inflammatory cells and in small vessels, but not in the tumor cells themselves.
  • Giving HA and C1q to the cells in soluble form did not work well. The supplementary figure reports no statistically significant differences.
  • MPM primary cells grown on the C1q–HA matrix had significantly higher HAS3 mRNA than cells on HA alone (eight MPM populations in triplicate, p less than 0.05). No significant change was observed for HAS1 and HAS2.
  • Western blot and flow cytometry confirmed higher HAS3 protein in MPM cells grown on the C1q and HA matrix (p less than 0.05).
  • In the TCGA mesothelioma dataset, patients with high HAS3 expression had lower survival than those with low expression (p less than 0.01). HAS1 and HAS2 expression did not appear to be related to survival. Patient numbers for this analysis are not given in the text.
• The authors' conclusion: The authors concluded that isolated MPM primary cells synthesize HA themselves (a coat around the cell, protrusions, and an internal pool), and that the C1q–HA matrix increases HAS3 expression. They identified HAS3 as a potential future target in MPM.
• Limitations the authors state:
  • In the fluorescence experiments, the HA coat outside the cells was lost during fixation. This prevented comparison of cells treated and untreated with hyaluronidase.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Hyaluronic Acid, Pleural Effusion, Life Expectancy.

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