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Low-dose cyclophosphamide induces anti-tumor T-cell responses which associate with survival in metastatic colorectal cancer

Scurr, Martin J, Pembroke, Tom, Bloom, Anja, Roberts, David J, Thomson, Amanda, Smart, Kathryn, Bridgeman, Hayley, Adams, Richard A, Brewster, Alison E, Jones, Robert, Gwynne, Sarah, Blount, Daniel, Harrop, Richard, Hills, Robert, Gallimore, Awen and Godkin, Andrew 2017. Low-dose cyclophosphamide induces anti-tumor T-cell responses which associate with survival in metastatic colorectal cancer. Clinical Cancer Research , clincanres.0895.2017. 10.1158/1078-0432.CCR-17-0895

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Purpose: Anti-cancer T-cell responses can control tumors, but immune-suppressive mechanisms in vivo prevent their function. The role of regulatory T-cells (Tregs) in metastatic colorectal cancer (mCRC) is unclear. We have previously shown depletion of Tregs enhances CRC-specific effector T-cell responses. Low dose cyclophosphamide (CPM) targets Tregs in animal models and some human studies, however the effect of CPM in mCRC is unknown. Experimental Design: Fifty-five mCRC patients were enrolled onto a phase I/II trial and randomized to receive two week-long courses of low-dose (50mg twice-a-day) CPM or not. The absolute number, phenotype and anti-tumor function of peripheral blood-derived lymphocyte subsets were monitored throughout treatment, along with 18-month follow-up. Results: Initially CPM reduced proliferation in all lymphocyte subsets, however, a rapid mobilization of effector T-cells overcame this decrease, leading to increased absolute T-cell numbers. In contrast, a reduction in proportional and absolute Treg, B-cell and NK-cell numbers occurred. The expansion and subsequent activation of effector T-cells was focused on tumor-specific T-cells, producing both granzyme B and IFN-gamma. CPM-treated patients demonstrating the most enhanced IFN-gamma+ tumor-specific T-cell responses exhibited a significant delay in tumor progression (HR=0.29, 95% CI 0.12-0.69, P=0.0047), compared to non-responders and no-treatment controls. Conclusions: CPM-induced Treg-depletion is mirrored by a striking boost to anti-tumor immunity. This study provides the first direct evidence of the benefit of naturally primed T-cells in mCRC patients. Our results also support the concept that non-mutated self-antigens can act as useful targets for immunotherapies.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Centre for Trials Research (CNTRR)
Subjects: R Medicine > R Medicine (General)
Publisher: American Association for Cancer Research
ISSN: 1078-0432
Date of First Compliant Deposit: 12 September 2017
Date of Acceptance: 8 August 2017
Last Modified: 27 May 2021 12:42

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