Chemokine Cxcl10-induced membrane colocalization of Cxcr3 and Egfr receptors in ING4-deficient breast cancer cells
Breast cancer is the most common form of cancer in women worldwide. Up to 34% of breast tumors are deficient in the tumor suppressor gene inhibitor of growth 4 (ING4), which is correlated with poor patient outcomes. The chemokine Cxcl10 has been shown to induce migration of ING4-deleted cells through crosstalk between its receptor, C-X-C chemokine receptor type 3 (Cxcr3), and the Epidermal growth factor receptor (Egfr). It is unknown where these receptors associate, or colocalize, on breast cancer cells. We hypothesized that Cxcl10 would induce colocalization of Cxcr3 and Egfr on the cell membrane, followed by a decrease due to receptor internalization. Immunofluorescent staining was used to visualize Cxcr3 and Egfr in permeabilized or non-permeabilized ING4-deleted MDA-MB-231 breast cancer cells treated with Cxcl10 for 0, 10 minutes, 1 hour, 4 hours, and 8 hours. Receptor colocalization was quantified using Manders M1 coefficient calculations. The results showed that Cxcl10 did not induce colocalization in permeabilized cells. In non-permeabilized cells, Cxcl10 induced transient colocalization at 10 minutes (p=0.049) and 1 hour (p=6.9E05). Notably, in non-permeabilized cells after 0, 10 minutes, 1 hour, and 8 hours of Cxcl10 treatment, novel Cxcr3 “cap” structures were observed on localized regions of the membrane. Further investigation of Cxcr3 “cap” structure staining in non-permeabilized cells will be conducted to determine if they have a role in Cxcl10-induced colocalization and/or cell migration. A better understanding of the mechanism underlying Cxcl10-induced migration in ING4-deleted breast cancer cells will enable the development of new therapies for metastatic breast cancer.
