Tumor relapse after chemotherapy-induced regression is a major clinical problem, because it often involves inoperable metastatic disease. Tumor-associated macrophages (TAM) are known to limit the cytotoxic effects of chemotherapy in preclinical models of cancer. Here, we report that an alternatively activated (M2) subpopulation of TAMs (MRC1+TIE2HiCXCR4Hi) accumulate around blood vessels in tumors after chemotherapy, where they promote tumor revascularization and relapse, in part, via VEGF-A release. A similar perivascular, M2-related TAM subset was present in human breast carcinomas and bone metastases after chemotherapy. Although a small proportion of M2 TAMs were also present in hypoxic tumor areas, when we genetically ablated their ability to respond to hypoxia via hypoxia-inducible factors 1 and 2, tumor relapse was unaffected. TAMs were the predominant cells expressing immunoreactive CXCR4 in chemotherapy-treated mouse tumors, with the highest levels expressed by MRC1+ TAMs clustering around the tumor vasculature. Furthermore, the primary CXCR4 ligand, CXCL12, was upregulated in these perivascular sites after chemotherapy, where it was selectively chemotactic for MRC1+ TAMs. Interestingly, HMOX-1, a marker of oxidative stress, was also upregulated in perivascular areas after chemotherapy. This enzyme generates carbon monoxide from the breakdown of heme, a gas known to upregulate CXCL12. Finally, pharmacologic blockade of CXCR4 selectively reduced M2-related TAMs after chemotherapy, especially those in direct contact with blood vessels, thereby reducing tumor revascularization and regrowth. Our studies rationalize a strategy to leverage chemotherapeutic efficacy by selectively targeting this perivascular, relapse-promoting M2-related TAM cell population.

Background and Aim: Despite widespread recommendations and use of intravenous corticosteroids (IVCS) for the treatment of acute flares of ulcerative colitis and Crohn's disease, limited evidence exists comparing outcomes of the two most common regimens, intravenous methylprednisolone (IVMP) and intravenous hydrocortisone (IVHC). IVHC has stronger mineralocorticoid effects compared with IVMP and may cause higher rates of hypokalemia. We aimed to determine differences in clinical outcomes including requirement for inpatient rescue therapy, bowel resection, and rates of hypokalemia. Methods: We conducted a multicenter cohort study of all adult patients admitted with an acute flare of inflammatory bowel disease (IBD) to the three tertiary hospitals in Auckland, New Zealand, where the protocol at each institution is either IVMP 60 mg daily or IVHC 100 mg four times daily. All patients requiring IVCS between 20 June 2016 and 30 June 2018 were included. The IVCS protocol was then changed at one hospital, where further data were collected for a further 12 months from 30 January 2019 until 30 December 2019. Results: There were 359 patients, including 129 (35.9%) patients receiving IVMP and 230 (64.1%) patients receiving IVHC. IVMP treatment was associated with a greater requirement for rescue therapy than IVHC (36.4% vs 19.6%, P = 0.001; odds ratio [OR] = 2.79; 95% confidence interval [CI], 1.64-4.75, P < 0.001), but also reduced rates of hypokalemia (55.8% vs 67.0%, P = 0.04; OR = 0.49; 95% CI, 0.30-0.81, P = 0.005). There was no difference between treatment groups for the median length of admission (5 days, interquartile range [IQR] 3-8), median duration of IVCS treatment (3 days, IQR 2-5), or bowel resection within 30 days of admission (12.4% vs 11.7%; OR = 1.04). Conclusion:For the treatment of an acute flare of IBD, treatment with IVMP results in significantly more requirement for inpatient rescue biologic or cyclosporin. In addition, it causes statistically significant less hypokalemia than IVHC, although in practice differences are negligible.

<p>Effects of various cytotoxic agents on TAM accumulation in three mouse tumor models (S1); Further Characterization of MRC1+ TAMs in mouse tumors (S2); VEGFA lmmunofluorescence in control and CTX-treated LLC1 tumors (S3); Role of hypoxic (ie. HIF-expressing) TAMs in relapse of LLC1 tumors after CTX (S4); Effect of CXCR4 blockade on various tumor parameters in CTX-treated LLC1 tumors (S5); Co-localization of HIFs 1 and 2, but not CXCL12 or HO-1, with hypoxia in LLC1s (S6); Effect of CXCR4 blockade on the longer-term re-growth kinetics of primary and metastatic LLC1s (S7).</p>

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Supplementary Figure Legends from Perivascular M2 Macrophages Stimulate Tumor Relapse after Chemotherapy

Supplementary Figure Legends from Perivascular M2 Macrophages Stimulate Tumor Relapse after Chemotherapy

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<p>Effects of various cytotoxic agents on TAM accumulation in three mouse tumor models (S1); Further Characterization of MRC1+ TAMs in mouse tumors (S2); VEGFA lmmunofluorescence in control and CTX-treated LLC1 tumors (S3); Role of hypoxic (ie. HIF-expressing) TAMs in relapse of LLC1 tumors after CTX (S4); Effect of CXCR4 blockade on various tumor parameters in CTX-treated LLC1 tumors (S5); Co-localization of HIFs 1 and 2, but not CXCL12 or HO-1, with hypoxia in LLC1s (S6); Effect of CXCR4 blockade on the longer-term re-growth kinetics of primary and metastatic LLC1s (S7).</p>