Suppression of Her2/neu expression through ILK inhibition is regulated by a pathway involving TWIST and YB-1.

In a previous study it was found that the therapeutic effects of QLT0267, a small molecule inhibitor of integrin-linked kinase (ILK), were influenced by Her2/neu expression. To understand how inhibition or silencing of ILK influences Her2/neu expression, Her2/neu signaling was evaluated in six Her2/neu-positive breast cancer cell lines (LCC6(Her2), MCF7(Her2), SKBR3, BT474, JIMT-1 and KPL-4). Treatment with QLT0267 engendered suppression (32-87%) of total Her2/neu protein in these cells. Suppression of Her2/neu was also observed following small interfering RNA-mediated silencing of ILK expression. Time course studies suggest that ILK inhibition or silencing caused transient decreases in P-AKT(ser473), which were not temporally related to Her2/neu downregulation. Attenuation of ILK activity or expression was, however, associated with decreases in YB-1 (Y-box binding protein-1) protein and transcript levels. YB-1 is a known transcriptional regulator of Her2/neu expression, and in this study it is demonstrated that inhibition of ILK activity using QLT0267 decreased YB-1 promoter activity by 50.6%. ILK inhibition was associated with changes in YB-1 localization, as reflected by localization of cytoplasmic YB-1 into stress granules. ILK inhibition also suppressed TWIST (a regulator of YB-1 expression) protein expression. To confirm the role of ILK on YB-1 and TWIST, cells were engineered to overexpress ILK. This was associated with a fourfold increase in the level of YB-1 in the nucleus, and a 2- and 1.5-fold increase in TWIST and Her2/neu protein levels, respectively. Taken together, these data indicate that ILK regulates the expression of Her2/neu through TWIST and YB-1, lending support to the use of ILK inhibitors in the treatment of aggressive Her2/neu-positive tumors.

Enforced epithelial expression of IGF-1 causes hyperplastic prostate growth while negative selection is requisite for spontaneous metastogenesis.

The insulin-like growth factor-1 (IGF-1) signaling axis is important for cell growth, differentiation and survival and increased serum IGF is a risk factor for prostate and other cancers. To study IGF-1 action on the prostate, we created transgenic (PB-Des) mice that specifically express human IGF-1(des) in prostate epithelial cells. This encodes a mature isoform of IGF-1 with decreased affinity for IGF binding proteins (IGFBP) due to a 3-amino acid deletion in the N terminus. Expression of IGF-1(des) was sufficient to cause hyperplastic lesions in all mice, however the well-differentiated lesions did not progress to adenocarcinoma within a year. Remarkably, crossing the PB-Des mice to an established model of prostate cancer delayed progression of organ-confined tumors and emergence of metastatic lesions in young mice. While dissemination of metastatic lesions was widespread in old bigenic mice we did not detect IGF-1(des) in poorly differentiated primary tumors or metastatic lesions. Expression of endogenous IGF-1 and levels of P-Akt and P-Erk were reduced independent of age. These data suggest that increased physiologic levels of IGF-1 facilitate the emergence of hyperplastic lesions while imposing a strong IGF-1-dependent differentiation block. Selection against IGF-1 action appears requisite for progression of localized disease and metastogenesis.

A Ras subfamily GTPase shows cell cycle-dependent nuclear localization.

Previously characterized Ras subfamily proteins have been found to be predominantly associated with the plasma membrane where they function in signal transduction pathways to convey extracellular signals to intracellular targets. Here, we provide evidence that the Dictyostelium Ras subfamily protein RasB has a novel subcellular localization and function. The protein is predominantly localized in the nucleus during most of the cell cycle. Furthermore, during mitosis and cytokinesis RasB assumes a diffuse cellular localization despite the fact that the nuclear membrane stays intact. The linkage between the position of RasB in the cell and division suggests that it may have a role in nuclear division. Consistent with this idea, rasB- cells exhibit severe growth defects and cells overexpressing an activated version of RasB are multinucleate.

Phylogenetic evidence for role-reversals of gender-associated mitochondrial DNA in Mytilus (Bivalvia: Mytilidae).

Distinct gender-associated mitochondrial DNA (mtDNA) lineages (i.e., lineages which are transmitted either through males or through females) have been demonstrated in two families of bivalves, the Mytilidae (marine mussels) and the Unionidae (freshwater mussels), which have been separated for more than 400 Myr. The mode of transmission of these M (for male-transmitted) and F (for female-transmitted) molecules has been referred to as doubly uniparental inheritance (DUI), in contrast to standard maternal inheritance (SMI), which is the norm in animals. A previous study suggested that at least three origins of DUI are required to explain the phylogenetic pattern of M and F lineages in freshwater and marine mussels. Here we present phylogenetic evidence based on partial sequences of the cytochrome c oxidase subunit I gene and the 16S RNA gene that indicates the DUI is a dynamic phenomenon. Specifically, we demonstrate that F lineages in three species of Mytilus mussels, M. edulis, M. trossulus, and M. californianus, have spawned separate lineages which are now associated only with males. This process is referred to as "masculinization" of F mtDNA. By extension, we propose that DUI may be a primitive bivalve character and that periodic masculinization events combined with extinction of previously existing M types effectively reset the time of divergence between conspecific gender-associated mtDNA lineages.