BECN1 (beclin 1) is a coiled-coil protein that has been implicated as an
inhibitor of tumorigenesis. BECN1, which associates with Bcl-2, plays a
significant role in autophagy. Autophagy is the degradation of cellular proteins
in the lysosomes, and when this pathway is suppressed, cell growth is
deregulated. Autophagy is controlled by the same signal transduction pathway
that induces the phosphorylation of the ribosomal protein S6, and both
are mediated via amino acids. BECN1 expression in various carcinoma cell
lines, such as MCF7, is low, whereas it is ubiquitously expressed in normal
breast tissue. In transfected MCF7 cells, BECN1 complements autophagocytosis
and, subsequently, inhibits cellular proliferation. Additionally, BECN1
shares structural similarity to the yeast autophagy gene product, APG6, and
was one of the first mammalian proteins discovered to mediate autophagy.