Asthma-related inflammation promotes lung metastasis of breast cancer cells through CCL11–CCR3 pathway

Background: Mechanisms that preclude lung metastasis are still barely understood. The possible consequences of allergic airways inflammation on cancer dissemination were studied in a mouse model of breast cancer.
Methods: Balb/c mice were immunized and daily exposed to ovalbumin (OVA) from day 21. They were subcutane- ously injected with 4T1 mammary tumor cells on day 45 and sacrificed on day 67. Lung metastases were measured by
biophotonic imaging (IVIS 200 Imaging System) and histological measurement of tumor area (Cytomine software). Effects of CCL11 were assessed in vivo by intratracheal instillations of recCCL11 and in vitro using Boyden chambers. CCR3 expression on cell surface was assessed by flow cytometry.
Results: The extent of tumor metastases was significantly higher in lungs of OVA-exposed mice and increased levels of CCL11 expression were measured after OVA exposure. Migration of 4T1 cells and neutrophils was stimulated in vitro and in vivo by recCCL11. 4T1 cells and neutrophils express CCR3 as shown by flow cytometry and a selective CCR3 antagonist (SB-297006) inhibited the induction of 4T1 cells migration and proliferation in response to recCCL11.
Conclusions: Allergic inflammation generated by exposure to allergens triggers the implantation of metastatic cells from primary breast tumor into lung tissues plausibly in a CCL11–CCR3-dependent manner. This indicates that asthma related inflammation in lungs might be a risk factor for lung metastasis in breast cancer patients.