Chronic infection by the hepatitis C virus (HCV) is a major cause of liver diseases, predisposing to fibrosis and hepatocellular carcinoma. Liver fibrosis is characterized by an overly abundant accumulation of components of the hepatic extracellular matrix, such as collagen and elastin, with consequences on the properties of this microenvironment and cancer initiation and growth. This review will provide an update on mechanistic concepts of HCV-related liver fibrosis/cirrhosis and early stages of carcinogenesis, with a dissection of the molecular details of the cross-talk during disease progression between hepatocytes, the extracellular matrix and hepatic stellate cells.
Virus |
HBV |
HCV |
---|---|---|
Viral family |
Hepadnaviridae |
Flaviviridae |
Genome |
DNA and cccDNA |
RNA |
Life cycle |
Genome integration, expression of HBx protein, insertional activation of cellular oncogenes, cccDNA (minichromosome) |
Exclusively cytoplasmic |
Persistence |
Nucleus-located cccDNA |
Chronic inflammation, oxidative stress, alterations in cellular signaling and metabolism |
HCV Proteins |
ECM Proteins or Cytokines |
---|---|
Capsid core |
LOX ∞ [61] Procollagen I ∞ [62] Collagen I ∞ [61] MMP-2 ∞ [58] |
MMP-9 ∞ [63] |
|
COX-2 ∞ [63] |
|
Syndecan-1 * [31] |
|
Thrombospondin-1 ∞ [61] |
|
CTGF ∞ [58] |
|
TGF-β2 ◊ [67] |
|
Endoglin ∞ [68] |
|
Envelope glycoproteins E1 and/or E2 |
Glypican-3 * [69] |
TGF-β1 ◊ [66] |
|
Cysteine autoprotease NS2 |
MICA ∞ [70] TGF-β2 ◊ [67] |
Serine protease and helicase NS3 |
Procollagen I ∞ [62] MMP-9 ∞ [71] |
COX-2 ∞ [71] |
|
Thrombospondin-1 [72] |
|
Osteopontin * [64] |
|
TGF-β type I receptor * [73] |
|
NS3 with its cofactor NS4A |
MMP-9 ∞ [71] |
COX-2 ∞ [71] MICA ∞ [74] |
|
NS4B |
MMP-2 ∞ [76] |
NS5A |
MMP-2 ∞ [63] |
MMP-9 ∞ [63] |
|
COX-2 ∞ [63] |
|
Thrombospondin-1 ∞ [72] |
|
Osteopontin * [64] |
|
RNA-dependent RNA polymerase NS5B |
Osteopontin * [64] |
MICA ∞ [70] TGF-β ◊ [75] |
ECM Proteins/Cytokine |
F0/F1 |
F2 |
F3 |
F4 |
HCC |
References |
---|---|---|---|---|---|---|
Collagens I, III, V |
F1 |
|||||
Collagen XII |
||||||
Collagen XIV |
||||||
Collagen XVI |
[59] |
|||||
Collagen XVIII |
[59] |
|||||
PIIINP |
F1 |
|||||
MMP-2, -7, -9 |
F1 |
|||||
TIMP-1 |
||||||
ADAM-TS1 |
[93] |
|||||
ADAM-TS2 |
[94] |
|||||
Xylosyltransferase-2 |
F1 |
|||||
Glypican-3 |
||||||
Hyaluronic acid |
||||||
Decorin |
F1 |
[92] |
||||
Biglycan |
[59] |
|||||
Fibromodulin |
[60] |
|||||
Lumican |
||||||
Versican |
F1 |
|||||
Tenascin-C |
||||||
Osteopontin |
F1 |
|||||
Fibronectin |
||||||
Fibronectin isoforms |
[108] |
|||||
Elastin |
||||||
MFAP-4 † |
F1 |
|||||
Fibulin-5 |
[84] |
|||||
TGF-β1 (protein, mRNA) |
||||||
TGF-β1 (serum levels) |
F1 |
|||||
TGF-β2 |
F1 |
F0 |
[67] |
|||
Endoglin (protein, serum levels) |
[100] |
|||||
Endoglin (mRNA) § |
[68] |
a Color codes: green, upregulation; dark green: higher upregulation; blue, downregulation; dark blue: higher downregulation; grey, no change; magenta, no correlation with liver fibrosis stage. † MFAP-4, microfibrillar-associated protein-4 (associated with elastin fibers). § Endoglin mRNA was found upregulated in chronically HCV-infected patients compared to noninfected patients but not correlating with liver fibrosis stage.
In the era of DAAs which raise hope of eradicating HCV, HCV infection still remains a leading cause of hepatic failure due to advanced liver disease and HCC, because curing the infection does not fully restore liver homeostasis. Furthermore, DAA treatment alone may not be sufficient for a complete cure of fibrosis, as several factors other than the virus contribute to liver deterioration. Lastly, patients under antiviral therapy variably respond to the regression of fibrosis. The mechanism of HCV-induced liver disease is a multifaceted process, since various host genes are altered, and since host cells respond to infection/viral components by mobilizing or producing enzymes, growth factors and chemokines which activate quiescent HSCs. HCV chronic infection leads to a deep remodeling of the entire liver ECM architecture, through direct interactions between viral, ECM and cellular proteins, and through indirect effects (e.g. promotion of oxidative and ER stress, of inflammation, of stemness). HCV-induced overexpression of TGF-b, the most potent profibrogenic cytokine, contributes to HCV replication, and to the activation of HSCs, the promotion of their survival, and the inhibition of HSC apoptosis, mechanisms by which liver disease progresses. Consequently, several general mechanisms involved in liver fibrosis/cirrhosis development contribute to tumorigenesis. TGF-b signaling facilitates HCV replication in hepatocytes, and could promote survival of pre-cancerous cells; furthermore, HCV replicates at higher rates in liver cancer stem cells.
Thus, efforts toward a deeper comprehension of host/virus/ECM interactions, and of the underlying mechanisms by which hepatic dysfunctions emerge, spread and persist after HCV infection are therefore still needed, in order to develop therapies that cure liver disease in addition to curing infection.References.
This entry is adapted from the peer-reviewed paper 10.3390/cancers13092270