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TLR4-Mediated Inflammation Promotes KSHV-Induced Cellular Transformation and Tumorigenesis by Activating the STAT3

Marion Gruffaz1, Karthik Vasan1, Brandon Tan1

  • 1Department of Molecular Microbiology and Immunology, Keck School of Medicine, University of Southern California, Los Angeles, California.

Cancer Research
|October 21, 2017
PubMed

Insights

Toll-like receptor 4 (TLR4) promotes Kaposi sarcoma by driving chronic inflammation and cell proliferation. Inhibiting TLR4 signaling reduces tumor growth, offering a potential therapeutic target for this cancer.

Area of Science:

  • Immunology
  • Oncology
  • Virology

Background:

  • Toll-like receptors (TLRs) are immune sensors involved in antimicrobial and antitumor responses.
  • Some TLRs, however, are implicated in promoting carcinogenesis.
  • Kaposi sarcoma, a cancer caused by KSHV, involves neoangiogenesis and inflammation.

Purpose of the Study:

  • To investigate the role of Toll-like receptor 4 (TLR4) in Kaposi sarcoma development.
  • To elucidate the mechanisms by which KSHV-induced TLR4 signaling contributes to tumorigenesis.

Main Methods:

  • Analysis of TLR4 expression in human Kaposi sarcoma lesions.
  • KSHV-induced cellular transformation model to study TLR4 pathway activation.
  • Assessment of cytokine induction (IL6, IL1β, IL18) and STAT3 pathway activation.
  • Evaluation of TLR4 stimulation and antagonism effects on tumorigenesis.

Main Results:

  • TLR4 was upregulated in KSHV-infected tumor cells.
  • KSHV induced TLR4 expression via viral microRNAs, leading to constitutive pathway activation.
  • Chronic inflammation (IL6, IL1β, IL18) and STAT3 activation were observed.
  • TLR4 stimulation enhanced tumorigenesis, while antagonism inhibited it.

Conclusions:

  • The TLR4 pathway plays a critical role in KSHV-induced tumorigenesis through chronic inflammation.
  • This pathway contributes to uncontrolled cell proliferation and transformation.
  • Findings help explain Kaposi sarcoma prevalence in HIV-infected individuals with opportunistic infections.

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