PLXNB3 and neoplasm: When limiting numbers of MDA-MB-231 cells were injected into the mammary fat pad (1 × 103 rather than 2 × 106 used in the prior experiment), tumors formed in 10 out of 10 mice injected with cells expressing a non-targeting control (NTC) shRNA but in only 3 or 4 of out of 10 mice injected with cells expressing either of 2 different shRNAs targeting PLXNB3, demonstrating a significant impairment of tumor formation by PLXNB3 loss of function.54