CD8+ T cells inhibit metastasis and CXCL4 regulates its function

Robiya Joseph1, Rama Soundararajan1, Suhas Vasaikar1

  • 1Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.

Abstract

Insights

Immune cells, specifically CD8+ T cells, inhibit cancer metastasis. However, platelets and CXCL4 can promote metastasis by generating myeloid-derived suppressor cells that suppress CD8+ T cell activity, impacting patient survival.

Area of Science:

  • Immunology
  • Oncology
  • Cancer Metastasis

Background:

  • The precise mechanisms by which immune cells influence cancer metastasis remain poorly understood.
  • Elucidating the role of immune cells in metastasis is crucial for developing novel therapeutic strategies to enhance patient survival.

Purpose of the Study:

  • To investigate the interplay between immune cells, platelets, and metastasis in tumor progression.
  • To identify key molecular players and cellular interactions that regulate the metastatic process.

Main Methods:

  • Utilized syngeneic orthotopic mouse tumor models, including knockout variants (CD8, CD4) and immunodeficient mice.
  • Administered CXCL4 and analyzed tumors and lungs for cancer cell dissemination via bioluminescence.
  • Isolated circulating tumor cells and performed immunohistochemistry on mouse tumors and a human triple-negative breast cancer (TNBC) tissue microarray.
  • Analyzed The Cancer Genome Atlas (TCGA) pan-cancer data from over 10,000 patients.

Main Results:

  • Discovered distinct intratumoral immune infiltration patterns in metastatic versus non-metastatic tumors.
  • Non-metastatic tumors exhibited high CD8+ T cell and low platelet levels, with the inverse observed in metastatic tumors.
  • Platelets and CXCL4 were shown to induce monocyte differentiation into myeloid-derived suppressor cells (MDSCs), which suppress CD8+ T cell function during tumor progression.
  • TCGA data analysis revealed significantly lower survival probability in patients with CD8lowPlatelethigh profiles compared to CD8highPlateletlow profiles.

Conclusions:

  • CD8+ T cells play a critical role in inhibiting cancer metastasis.
  • Disruption of the balance between CD8+ T cells and platelets leads to CXCL4 production by platelets, inducing MDSCs and consequently inhibiting CD8+ T cell-mediated anti-metastatic activity.

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