Transcriptional and translational regulation of the expression of the l(2)gl tumor suppressor gene of Drosophila melanogaster

The cancer puzzle: Welcome to organicism

During the fifty years since President Nixon declared the "War on Cancer", those inside and outside the cancer community have witnessed the systematic moving of the goalposts attitude to accommodate evidence into an inadequate theory, that is, the Somatic Mutation Theory (SMT). This sorry state promoted a renewable yearly promise that at the end of the next 10-year period the promises uttered in 1971 would become reality. Each failure triggered calls to do more of the same research under the same theory, routinely using more and more sophisticated technology. Meanwhile, in the last few years, an unambiguous general consensus has emerged acknowledging that this overall long, intensive effort has failed, and that it is likely that the solution to the cancer problem resides elsewhere, namely, in alternative theoretical principles of biology. In this essay we concentrate, first, on the big picture, from the philosophical stance (reductionism versus organicism) to the need to adopt rigorous theories. From this novel perspective we conceptualize cancer as a disease of tissue organization akin to development gone awry. Finally, having identified both a promising stance and a useful theory, i.e., the tissue organization field theory (TOFT), we call for abandoning the SMT and for adopting the more promising TOFT.

The timing of drosophila salivary gland apoptosis displays an l(2)gl-dose response

During Drosophila metamorphosis, larval tissues, such as the salivary glands, are histolysed whereas imaginal tissues differentiate into adult structures forming at eclosion a fly-shaped adult. Inactivation of the lethal(2)giant larvae (l(2)gl) gene encoding the cytoskeletal associated p127 protein, causes malignant transformation of brain neuroblasts and imaginal disc cells with developmental arrest at the larval-pupal transition phase. At this stage, p127 is expressed in wild-type salivary glands which become fully histolysed 12 - 13 h after pupariation. By contrast to wild-type, administration of 20-hydroxyecdsone to l(2)gl-deficient salivary glands is unable to induce histolysis, although it releases stored glue granules and gives rise to a nearly normal pupariation chromosome puffing, indicating that p127 is required for salivary gland apoptosis. To unravel the l(2)gl function in this tissue we used transgenic lines expressing reduced ( approximately 0.1) or increased levels of p127 (3.0). Here we show that the timing of salivary gland histolysis displays an l(2)gl-dose response. Reduced p127 expression delays histolysis whereas overexpression accelerates this process without affecting the duration of third larval instar, prepupal and pupal development. Similar l(2)gl-dependence is noticed in the timing of expression of the cell death genes reaper, head involution defective and grim, supporting the idea that p127 plays a critical role in the implementation of ecdysone-triggered apoptosis. These experiments show also that the timing of salivary gland apoptosis can be manipulated without affecting normal development and provide ways to investigate the nature of the components specifically involved in the apoptotic pathway of the salivary glands.

Expanded: a gene involved in the control of cell proliferation in imaginal discs

The expanded gene was first identified by a spontaneous mutation that causes broad wings. We have identified an enhancer-trap insertion within expanded and used it to generate additional mutations, including one null allele. expanded is an essential gene, necessary for proper growth control of imaginal discs and, when mutant, causes either hyperplasia or degeneration depending on the disc. Wing overgrowth in expanded hypermorphs is limited to specific regions along the anterior-posterior and dorsal-ventral axis. expanded encodes a novel 1429 amino acid protein that is localized to the apical surface of disc cells and contains three potential SH3-binding sites. Together, these observations suggest that the Expanded protein engages in protein-protein interactions regulating cell proliferation in discs.