BECN1 and cancer: However, despite such clear evidence that autophagy prevents cancer development, it has also been shown that amongst immortalized, apoptosis-defective mouse mammary epithelial cells, beclin 1+/+ cells are more resistant to cell death upon nutrient and oxygen deprivation and survive longer compared to beclin 1+/- cells, suggesting that autophagy may be activated to promote cell survival in apoptosis-defective cells [37, 45].