Ischemia exists in many diseased tissues, including arthritic joints, atherosclerotic plaques, and malignant tumors. Macrophages accumulate in these sites and up-regulate hypoxia-inducible transcription factors (HIFs) 1 and 2 in response to the hypoxia present. Here we show that the gene expression profile in primary human and murine macrophages changes markedly when they are exposed to hypoxia for 18 hours. For example, they were seen to up-regulate the cell surface receptors, CXCR4 and GLUT1, and the potent, tumor-promoting cytokines, vascular endothelial growth factor A, interleukin (IL)-1β and IL-8, adrenomedullin, CXCR4, and angiopoietin-2. Hypoxia also stimulated their expression and/or phosphorylation of various proteins in the nuclear factor-κB (NF-κB) signaling pathway. We then used both genetic and pharmacologic methods to manipulate the levels of HIFs-1α and 2α or NF-κB in primary macrophages to elucidate their role in the hypoxic induction of many of these key genes. These studies showed that both HIF-1 and -2, but not NF-κB, are important transcriptional effectors regulating the responses of macrophages to such a period of hypoxia. Further studies using experimental mouse models are now warranted to investigate the role of such macrophage responses in the progression of various diseased tissues, such as malignant tumors.

New therapies are required to target hypoxic areas of tumors as these sites are highly resistant to conventional cancer therapies. Monocytes continuously extravasate from the bloodstream into tumors where they differentiate into macrophages and accumulate in hypoxic areas, thereby opening up the possibility of using these cells as vehicles to deliver gene therapy to these otherwise inaccessible sites. We describe a new cell-based method that selectively targets an oncolytic adenovirus to hypoxic areas of prostate tumors. In this approach, macrophages were cotransduced with a hypoxia-regulated E1A/B construct and an E1A-dependent oncolytic adenovirus, whose proliferation is restricted to prostate tumor cells using prostate-specific promoter elements from the TARP, PSA, and PMSA genes. When such cotransduced cells reach an area of extreme hypoxia, the E1A/B proteins are expressed, thereby activating replication of the adenovirus. The virus is subsequently released by the host macrophage and infects neighboring tumor cells. Following systemic injection into mice bearing subcutaneous or orthotopic prostate tumors, cotransduced macrophages migrated into hypoxic tumor areas, upregulated E1A protein, and released multiple copies of adenovirus. The virus then infected neighboring cells but only proliferated and was cytotoxic in prostate tumor cells, resulting in the marked inhibition of tumor growth and reduction of pulmonary metastases. This novel delivery system employs 3 levels of tumor specificity: the natural “homing” of macrophages to hypoxic tumor areas, hypoxia-induced proliferation of the therapeutic adenovirus in host macrophages, and targeted replication of oncolytic virus in prostate tumor cells. Cancer Res; 71(5); 1805–15. ©2011 AACR.

Purpose: Barrett's esophagus represents an early stage in carcinogenesis leading to esophageal adenocarcinoma. Considerable evidence supports a major role for chronic inflammation and diverse chemokine pathways in the development of Barrett's esophagus and esophageal adenocarcinoma. Experimental Design: Here we utilized an IL1β transgenic mouse model of Barrett's esophagus and esophageal adenocarcinoma and human patient imaging to analyze the importance of CXCR4-expressing cells during esophageal carcinogenesis. Results: IL1β overexpression induces chronic esophageal inflammation and recapitulates the progression to Barrett's esophagus and esophageal adenocarcinoma. CXCR4 expression is increased in both epithelial and immune cells during disease progression in pL2-IL1β mice and also elevated in esophageal adenocarcinoma patient biopsy samples. Specific recruitment of CXCR4-positive (CXCR4+) immune cells correlated with dysplasia progression, suggesting that this immune population may be a key contributor to esophageal carcinogenesis. Similarly, with progression to dysplasia, there were increased numbers of CXCR4+ columnar epithelial cells at the squamocolumnar junction (SCJ). These findings were supported by stronger CXCR4-related signal intensity in ex vivo fluorescence imaging and autoradiography with advanced dysplasia. Pilot CXCR4-directed PET/CT imaging studies in patients with esophageal cancer demonstrate the potential utility of CXCR4 imaging for the diagnosis and staging of esophageal cancer. Conclusion: In conclusion, the recruitment of CXCR4+ immune cells and expansion of CXCR4+ epithelial cells in esophageal dysplasia and cancer highlight the potential of CXCR4 as a biomarker and molecular target for diagnostic imaging of the tumor microenvironment in esophageal adenocarcinoma. Clin Cancer Res; 24(5); 1048–61. ©2017 AACR.

Purpose: It was previously demonstrated that radiation effects can enhance the therapy outcome of immune checkpoint inhibitors. In this study, a syngeneic breast tumor mouse model was used to investigate the effect of [¹⁷⁷Lu]Lu-DOTA-folate as an immune stimulus to enhance anti-CTLA-4 immunotherapy.Methods: In vitro and in vivo studies were performed to characterize NF9006 breast tumor cells with regard to folate receptor (FR) expression and the possibility of tumor targeting using [¹⁷⁷Lu]Lu-DOTA-folate. A preclinical therapy study was performed over 70 days with NF9006 tumor-bearing mice that received vehicle only (group A); [¹⁷⁷Lu]Lu-DOTA-folate (5 MBq; 3.5 Gy absorbed tumor dose; group B); anti-CTLA-4 antibody (3 × 200 μg; group C), or both agents (group D). The mice were monitored regarding tumor growth over time and signs indicating adverse events of the treatment.Results: [¹⁷⁷Lu]Lu-DOTA-folate bound specifically to NF9006 tumor cells and tissue in vitro and accumulated in NF9006 tumors in vivo. The treatment with [¹⁷⁷Lu]Lu-DOTA-folate or an anti-CTLA-4 antibody had only a minor effect on NF9006 tumor growth and did not substantially increase the median survival time of mice (23 day and 19 days, respectively) as compared with untreated controls (12 days). [¹⁷⁷Lu]Lu-DOTA-folate sensitized, however, the tumors to anti-CTLA-4 immunotherapy, which became obvious by reduced tumor growth and, hence, a significantly improved median survival time of mice (> 70 days). No obvious signs of adverse effects were observed in treated mice as compared with untreated controls.Conclusion: Application of [¹⁷⁷Lu]Lu-DOTA-folate had a positive effect on the therapy outcome of anti-CTLA-4 immunotherapy. The results of this study may open new perspectives for future clinical translation of folate radioconjugates.