Dissection of c-myc domains involved in S phase induction of NIH 3T3 fibroblasts

The product of the c-myc proto-oncogene is an important regulator of cell proliferation and apoptosis in murine fibroblasts. Addition of the tumor promoter, phorbol myristate acetate (PMA), prevents apoptotic cell death induced by low serum concentrations in NIH3T3 cells that constitutively express and are transformed by v-myc. The protective effect of PMA allowed us to analyse the ability of normal c-Myc and Myc deletion mutants to induce serum starved, untransformed NIH3T3 cells to enter S phase. By microinjecting these quiescent cells with wild type and mutant human c-myc plasmids, we showed that full length c-myc is able to induce S phase entry in presence of PMA, but that c-Myc mutants that delete amino acids delta 7/91, delta 41/53, delta 56/103, delta 106/143, delta 265/317 and delta 414/433 are totally inactive. c-Myc did not shorten the period before entry into S phase, since Myc overexpressing cells entered S phase with the same kinetics as control cells when both were stimulated with 20% fetal calf serum (FCS). However, c-Myc overexpression did increase the percentage of cells entering S phase when these cells were stimulated with 2% fetal calf serum. Interestingly, this ability to enhance stimulation by a suboptimal concentration of FCS was retained to a significant degree by Myc mutants that delete amino acids delta 41/53, delta 56/103 or delta 265/317. Finally, Myc mutants that delete delta 106/143 or delta 414/433 exerted a dominant negative effect on S phase entry both in quiescent cells stimulated with 2% FCS and in unsynchronized, cycling cells

Conditional ROCK activation in vivo induces tumor cell dissemination and angiogenesis

Progression of tumors to invasive and metastatic forms requires that tumor cells undergo dramatic morphologic changes, a process regulated by Rho GTPases. Elevated expression of RhoA and RhoC, as well as the Rho effector proteins ROCK I and ROCK II, are commonly observed in human cancers and are often associated with more invasive and metastatic phenotypes. To examine how ROCK contributes to the progression of solid tumors, we established a conditionally activated form of ROCK II by fusing the kinase domain to the estrogen receptor hormone-binding domain (ROCK:ER). ROCK: ER-expressing colon carcinoma cells grown as tumors in immunocompromised nude mice organized into discrete clusters surrounding blood vessels. However, ROCKER activation resulted in the aggressive dissemination of tumor cells into the surrounding stroma, indicating that increased ROCK signaling is sufficient to promote invasion from solid tumors. In addition, tumors in which ROCKER was activated were more highly vascularized, indicating that ROCK contributes to tumor angiogenesis. ROCKER activation resulted in changes to epithelial morphology and organization that facilitated motility in vitro, likely by inducing the redistribution of proteins such as ezrin, as well as adherens junction and extracellular matrix-binding proteins. These results suggest that ROCK inhibitors would be useful antimetastatic and antiangiogenic chemotherapeutic agents in tumors associated with elevated RhoA, RhoC, ROCK I, or ROCK II expression

The Egyptian Predynastic and State Formation

When the archaeology of Predynastic Egypt was last appraised in this journal, Savage (2001a, p. 101) expressed optimism that “a consensus appears to be developing that stresses the gradual development of complex society in Egypt.” The picture today is less clear, with new data and alternative theoretical frameworks challenging received wisdom over the pace, direction, and nature of complex social change. Rather than an inexorable march to the beat of the neo-evolutionary drum, primary state formation in Egypt can be seen as a more syncopated phenomenon, characterized by periods of political experimentation and shifting social boundaries. Notably, field projects in Sudan and the Egyptian Delta together with new dating techniques have set older narratives of development into broader frames of reference. In contrast to syntheses that have sought to measure abstract thresholds of complexity, this review of the period between c. 4500 BC and c. 3000 BC transcends analytical categories by adopting a practice-based examination of multiple dimensions of social inequality and by considering how the early state may have become a lived reality in Egypt around the end of the fourth millennium BC