Abstract
To the Editor,
The recent article by Liu et al was highly stimulating (1). Beclin 1 may be a significant biomarker of prognosis in a number of systemic malignancies besides bladder carcinomas.
Malignant gastric tissue shows increased beclin 1 expression. Nearly 84% of all gastric malignancies demonstrate increased beclin 1 levels (2). In fact, beclin 1 is an independent parameter influencing clinical prognosis in gastric carcinomas, especially in stages III and IV. An inverse relationship exists between beclin 1 expression and bcl-xL expression (3). More aggressive gastric carcinomas tend to show downregulated beclin 1 levels. As a result, low beclin 1 expression is associated with decreased progression-free survival. Similarly, beclin 1 downregulation is seen in pancreatic malignancies. Beclin-1 attenuates intratumoral autophagy and thereby influences tumor progression in pancreatic carcinomas (4).
Likewise, beclin 1 is essential for cancer stem cells in breast malignancies (5). It is thus necessary for tumor progression. Mammary malignancies tend to demonstrate significantly lower beclin 1 levels than benign breast tissue (6). Not surprisingly, lower expression of beclin 1 is associated with decreased tumor differentiation. An inverse relationship exists between beclin 1 and bcl-2 expression in breast carcinomas (7).
On the other hand, upregulation of beclin 1 in cervical carcinomas has an attenuating effect on tumor growth (8). These effects have been seen both in vivo and in vitro. Beclin 1 does this by enhancing tumor apoptosis as well as autophagy. Part of these effects may be mediated by virtue of its modulation of intratumoral Ang-1 and Ang-2 (9). Not surprisingly, transfection of cervical malignancies with beclin 1 can result in tumor attenuation with inhibition rates as high as 52% having being reported (10). Tie-2 levels are also altered and vary with beclin 1 expression.
The above examples clearly illustrate the significant role of beclin 1 as a tumor biomarker in different systemic malignancies and the necessity to increase awareness about it amongst oncologists.