Taken together, the results thus far raise the possibility that Vav1 in lung cancer cells instigates a positive feed forward loop, which is amplified in the presence of macrophages: Vav1 stimulation induces cytokine secretion, which in turn activate macrophages to upregulate Vav1 expression (and possibly other cytokines such as EGF as well), resulting in increased ERK activation. Here, EGF is linked to lung carcinoma.