Additionally, we observed that the heterogeneous loss of ephrin-A5 in the ephrin-A5+/−Smo genotype failed to bring about a statistically significant decrease in tumor size as compared to ephrin-A5+/+Smo controls (data not shown), suggesting that total ablation of ephrin-A5 expression is necessary for tumor growth inhibition. The gene discussed is EFNA5; the disease is neoplasm.