Asymmetric division of adult stem cells generates one self-renewing stem cell and one differentiating cell, thereby maintaining tissue homeostasis. A decline in stem cell function has been proposed to contribute to tissue aging, although the underlying mechanism is poorly understood. Here, we show that changes in the stem cell orientation with respect to the niche during aging contribute to the decline in spermatogenesis in Drosophila male germ line. Throughout the cell cycle, centrosomes in germ line stem cells (GSCs) are oriented within their niche and ensures asymmetric division. We found that GSCs containing misoriented centrosomes accumulate with age and that these GSCs are arrested or delayed in the cell cycle. The cell cycle arrest is transient, and GSCs appear to re-enter cell cycle upon correction of centrosome orientation. Based on these findings, we propose that cell cycle arrest associated with centrosome misorientation functions as a mechanism to ensure asymmetric stem cell division, and that the inability of stem cells to maintain correct orientation during aging contributes to the decline in spermatogenesis. We further show that some of misoriented GSCs likely originate from dedifferentiation of spermatogonia.

The capacity of tumour cells to maintain continual overgrowth potential has been linked to the commandeering of normal self-renewal pathways. Using an epithelial cancer model in Drosophila melanogaster, we carried out an overexpression screen for oncogenes capable of cooperating with the loss of the epithelial apico-basal cell polarity regulator, scribbled (scrib), and identified the cell fate regulator, Abrupt, a BTB-zinc finger protein. Abrupt overexpression alone is insufficient to transform cells, but in cooperation with scrib loss of function, Abrupt promotes the formation of massive tumours in the eye/antennal disc. The steroid hormone receptor coactivator, Taiman (a homologue of SRC3/AIB1), is known to associate with Abrupt, and Taiman overexpression also drives tumour formation in cooperation with the loss of Scrib. Expression arrays and ChIP-Seq indicates that Abrupt overexpression represses a large number of genes, including steroid hormone-response genes and multiple cell fate regulators, thereby maintaining cells within an epithelial progenitor-like state. The progenitor-like state is characterised by the failure to express the conserved Eyes absent/Dachshund regulatory complex in the eye disc, and in the antennal disc by the failure to express cell fate regulators that define the temporal elaboration of the appendage along the proximo-distal axis downstream of Distalless. Loss of scrib promotes cooperation with Abrupt through impaired Hippo signalling, which is required and sufficient for cooperative overgrowth with Abrupt, and JNK (Jun kinase) signalling, which is required for tumour cell migration/invasion but not overgrowth. These results thus identify a novel cooperating oncogene, identify mammalian family members of which are also known oncogenes, and demonstrate that epithelial tumours in Drosophila can be characterised by the maintenance of a progenitor-like state.

Elk-1 belongs to the ternary complex factors (TCFs) subfamily of the ETS domain proteins, and plays a critical role in the expression of immediate-early genes (IEGs) upon mitogen stimulation and activation of the mitogen-activated protein kinase (MAPK) cascade. The association of TCFs with serum response elements (SREs) on IEG promoters has been widely studied and a role for Elk-1 in promoting cell cycle entry has been determined. However, the presence of the ETS domain transcription factor Elk-1 in axons and dendrites of post-mitotic adult brain neurons has implications for an alternative function for Elk-1 in neurons other than controlling proliferation. In this study, possible alternative roles for Elk-1 in neurons were investigated, and it was demonstrated that blocking TCF-mediated transactivation in neuronal cells leads to apoptosis through a caspase-dependent mechanism. Indeed RNAi-mediated depletion of endogenous Elk-1 results in increased caspase activity. Conversely, overexpression of either Elk-1 or Elk-VP16 fusion proteins was shown to rescue PC12 cells from chemically-induced apoptosis, and that higher levels of endogenous Elk-1 correlated with longer survival of DRGs in culture. It was shown that Elk-1 regulated the Mcl-1 gene expression required for survival, and that RNAi-mediated degradation of endogenous Elk-1 resulted in elimination of the mcl-1 message. We have further identified the survival-of-motor neuron-1 (SMN1) gene as a novel target of Elk-1, and show that the ets motifs in the SMN1 promoter are involved in this regulation.

During tumorigenesis, pathways that promote the epithelial-to-mesenchymal transition (EMT) can both facilitate metastasis and endow tumor cells with cancer stem cell properties. To gain a greater understanding of how these properties are interlinked in cancers we used Drosophila epithelial tumor models, which are driven by orthologues of human oncogenes (activated alleles of Ras and Notch) in cooperation with the loss of the cell polarity regulator, scribbled (scrib). Within these tumors, both invasive, mesenchymal-like cell morphology and continual tumor overgrowth, are dependent upon Jun N-terminal kinase (JNK) activity. To identify JNK-dependent changes within the tumors we used a comparative microarray analysis to define a JNK gene signature common to both Ras and Notch-driven tumors. Amongst the JNK-dependent changes was a significant enrichment for BTB-Zinc Finger (ZF) domain genes, including chronologically inappropriate morphogenesis (chinmo). chinmo was upregulated by JNK within the tumors, and overexpression of chinmo with either RasV12 or Nintra was sufficient to promote JNK-independent epithelial tumor formation in the eye/antennal disc, and, in cooperation with RasV12, promote tumor formation in the adult midgut epithelium. Chinmo primes cells for oncogene-mediated transformation through blocking differentiation in the eye disc, and promoting an escargot-expressing stem or enteroblast cell state in the adult midgut. BTB-ZF genes are also required for Ras and Notch-driven overgrowth of scrib mutant tissue, since, although loss of chinmo alone did not significantly impede tumor development, when loss of chinmo was combined with loss of a functionally related BTB-ZF gene, abrupt, tumor overgrowth was significantly reduced. abrupt is not a JNK-induced gene, however, Abrupt is present in JNK-positive tumor cells, consistent with a JNK-associated oncogenic role. As some mammalian BTB-ZF proteins are also highly oncogenic, our work suggests that EMT-promoting signals in human cancers could similarly utilize networks of these proteins to promote cancer stem cell states.

Cyclooxygenase enzymes play a vital role in inflammatory pathways in the human body. Apart from their relation with inflammation, the additional involvement of COX-2 enzyme with cancer activity was recently discovered. In some cancer types the level of COX-2 enzyme is increased indicating that this enzyme could be a suitable target for cancer therapy. Based on these findings, we have synthesized some new diflunisal thiosemicarbazides and 1,2,4-triazoles and tested them against androgen-independent prostate adenocarcinoma (PC-3), colon carcinoma (HCT-116), human breast cancer (T47D), breast carcinoma (MCF7) and human embryonic kidney (HEK-293) cell lines. Specifically, the diflunisal and thiosemicarbazide functionality are combined during the synthesis of original compounds anticipating a potency enhancement. Compounds 6, 10, 15 and 16 did not show cytotoxic effects for the HEK293 cell line. Among them, compounds 15 and 16 demonstrated anticancer activity for the breast cancer cell line T47D, whereas compounds 6 and 10 which are thiosemicarbazide derivatives displayed anti-tumourigenic activity against the PC-3 cell line, consistent with the literature. However, no activity was observed for the HCT-116 cancer cell line with the tested thiosemicarbazide derivatives. Only compound 16 displayed activity against the HCT-116 cell line. Therefore, it was speculated that the diflunisal and thiosemicarbazide functionalities potentiate anticancer activity on prostate cancer and the thiosemicarbazide functionality decreases the anticancer activity of diflunisal on colon cancer cell lines. In order to gain insight into the anticancer activity and COX-2 inhibition, molecular docking studies were carried out for COX-1 and COX-2 enzymes utilizing the newly synthesized compounds 15, and 16. Both 15 and 16 showed high selectivity and affinity toward COX-2 isozyme over COX-1, which is in agreement with the experimental results.