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EP017/#738  Insights from ovarian cancer patients’ rapid autopsy shed light on mechanisms of CD4+ T cell-mediated pre-metastatic niche formation through the STAT3 axis
  1. Antons Martincuks1,
  2. Rosemary Senguttuvan2,
  3. Maciej Kujawski1,
  4. Saul Priceman1,
  5. Eliza Barragan3,
  6. Kena Ihle3,
  7. Ernest Han2,
  8. Jeff Lin2,
  9. Lorna Rodriguez-Rodriguez2,
  10. Hua Yu1 and
  11. Mihae Song2
  1. 1City of Hope, Immuno-Oncology, Duarte, USA
  2. 2City of Hope, Gynecologic Oncology, Duarte, USA
  3. 3City of Hope, Precision Medicine, Duarte, USA


Introduction Whether adaptive immune cells are required for the formation of pre-metastatic niches critical for tumor metastasis remains unknown. Prior research indicates that Signal transducer and activator of transcription 3 (STAT3) contributes to the accumulation and function of innate immune cells in these niches. This study investigates whether CD4+ T cells can directly condition future metastatic sites and if STAT3 is necessary for CD4+ T cell-mediated niche formation.

Methods We evaluated CD4+ T cell infiltration in non-metastatic lung regions of mice and examined the role of STAT3 signaling using CD4Cre-Stat3Flox transgenic mice lacking functional Stat3 in T cells. Clinical correlations in ovarian cancer patients‘ disease-free lung and liver tissue sites from rapid autopsy tissue collection were also analyzed.

Results Our findings reveal that CD4+ T cells accumulate in distant tumor-free sites, forming pre-metastatic niches and subsequently promoting tumor metastasis in mice. Moreover, STAT3 activation is necessary for CD4+ T cell-mediated pre-metastatic niche formation. Depleting CD4+ T cells and STAT3 activation prior to primary tumor establishment significantly reduced tumor growth and almost completely blocked spontaneous lung metastasis, as evidenced in CD4-Stat3–/– mice. Importantly, analysis of presumed disease-free lung and liver tissue sites of ovarian cancer patients showed CD4+ T cell accumulation with activated STAT3 in non-tumor regions and surrounding micro-metastases.

Conclusion/Implications Blocking the pre-metastatic niche has the potential to prevent tumor cell seeding at distant sites, and our studies now show that targeting STAT3 in CD4+ T cells may be an effective strategy to prevent tumor metastasis.

Abstract EP017/#738 Figure 1

CD4+ T cells accumulate to form pre-metastatic niches in the lung and Srat3 ablation in T cells reduces pre-metastatic niche formation and tumor metastasis. A. In contrast tumor-free mice (top left panel), non-metastatic regions in the lungs of C57BL6 mice bearing MB49 bladder carcinomas are highly infiltrated by CD4+ T cells (top right panel), Frozen lung tissues analyzed by immunofluorescence, CD4: red; Hoechst 33342: blue, B. TCM derived trom ID8 ovarian tumor cell lines induce CD4+ T cell infiltration in the lung as early as 24hr post i.v. injection, as compared to control media, shown by immunofluorecsence staining and quantification of CD4+ T cells. Data are shown as averages ± SEM. C. Metastatic nodules were not detectable (ND) in MB49 tumor bearing CD4.Stat3-/- mice in comparison to Stat3+/+ mice with similar primary tumor size. Representative images of lung-associated tumor nodules and quantification per lung, n = 8.9 mice per group. Data are shown as averages ± SEM. D. Non-metastatic regions of lungs of CD4-Stat3-/- mice bearing MB49 tumors are significantly less infiltrated by CD4+ T cells in contrast to CD4-Stat3+/+ mice. The majority of CD4+ T cells in Stat3+/+ mice showed Stat3 activation. Representative staining of CD4+ T cells (red) and p-Stat3 (green) in the lung and CD4 quantification, right panel; n = 10 analyzed tissue regions per group. Data are shown as averages ± SEM

Abstract EP017/#738 Figure 2

CD4+ T cells accumulate in tumor-free lung and liver tissues of ovarian cancer patients. p-STAT3 positive CD4+ T cells accumulate around p-STAT3-expressing micro-metastases. A. In contrast to tumor and tumor proximal regions, distal non-metastatic regions in the lungs of ovarian cancer patients are highly infiltrated by CD4+ T cells. B. Non-metastatic regions of ovarian cancer livers are highly infiltrated by CD4+ T cells as well FFPE lung and liver tissues from Rapid Autopsy program were analyzed by immunofluorescence, CD4: magenta, Hoechst 33342: blue. C. Representative images of lung and liver-associated cytokeratin-stained micro-metastases with high nuclear p-STAT3 levels and surrounding p-STAT3-posltive CD4+ T cells in lung and liver tissues of ovanan cancer patients that passed from the disease. CD4: magenta, Hoechst 33342: blue; pan-Cytokeratin: red p-STAT3 green

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