Mechanisms underlying the cooperation between loss of epithelial polarity and Notch signaling during neoplastic growth in Drosophila

Aggressive neoplastic growth can be initiated by a limited number of genetic alterations, such as the well-established cooperation between loss of cell architecture and hyperactive signaling pathways. However, our understanding of how these different alterations interact and influence each other remains very incomplete. Using Drosophila paradigms of imaginal wing disc epithelial growth, we have monitored the changes in Notch pathway activity according to the polarity status of cells (scrib mutant). We show that the scrib mutation impacts the direct transcriptional output of the Notch pathway, without altering the global distribution of Su(H), the Notch dedicated transcription factor. The Notch-dependent neoplasms require however, the action of a group of transcription factors, similar to those previously identified for Ras/scrib neoplasm (namely AP-1, Stat92E, Ftz-F1, and bZIP factors), further suggesting the importance of this transcription factor network during neoplastic growth. Finally our work highlights some Notch/scrib specificities, in particular the role of the PAR domain containing bZIP transcription factor and Notch direct target Pdp1 for neoplastic growth.

Normal and Neoplastic Growth Suppression by The Extended Myc Network

Among the first discovered and most prominent cellular oncogenes is MYC, which encodes a bHLH-ZIP transcription factor (Myc) that both activates and suppresses numerous genes involved in proliferation, energy production, metabolism and translation. Myc belongs to a small group of bHLH-ZIP transcriptional regulators (the Myc Network) that includes its obligate heterodimerization partner Max and six “Mxd proteins” (Mxd1-4, Mnt and Mga) each of which heterodimerizes with Max and largely oppose Myc’s functions. More recently, a second group of bHLH-ZIP proteins (the Mlx Network) has emerged. It is comprised of the Myc-like factors ChREBP and MondoA, which, in association with the Max-like member Mlx, regulate smaller and more functionally restricted sets of target genes, some of which are shared with Myc. Opposing ChREBP and MondoA are heterodimers comprised of Mlx and Mxd1, Mxd4 and Mnt, which also structurally and operationally link the two Networks. We discuss here the functions of these “Extended Myc Network” members with particular emphasis on the roles played by Max, Mlx and Mxd proteins in suppressing normal and neoplastic growth. These roles are complex due to the temporally- and tissue-restricted expression of Extended Myc Network proteins in normal cells, their regulation of both common and unique target genes and, in some cases, their functional redundancy.

Nutritional AGEing and RAGEing as a Regulator of the Tumor Microenvironment

Objectives Advanced glycation end products (AGEs) are reactive metabolites formed endogenously by glyoxidative, oxidative and lipoxidative stresses. Foods associated with modern dietary habits are particularly AGE laden but despite increasing epidemiological evidence for oncogenic potential, cause and effect relationships are lacking. The objective was to provide detailed mechanistic insight and in vivo confirmation that AGEs found in the diet are oncogenic drivers of tumorigenesis. Methods We used the heat driven formation of glyoxidative, oxidative and lipoxidative stresses in experimental mouse chow to reproduce the wide spectrum of the AGEs found in vivo. Syngeneic xenograft and spontaneous prostate and breast cancer mouse models were then fed the AGE specific diets and the effects of chronic AGE consumption on tumor growth assessed. To gain mechanistic insight, human and mouse two compartment co-culture models using primary fibroblasts and matched tumor epithelial cells were then used to assess the effects of AGEs on extracellular crosstalk in the TME. Results A high impact finding from our research is that consumption of AGEs found in our diet promotes prostate tumor growth, aggression and metastasis by functioning as ligand to the transmembrane receptor for AGE (RAGE). Dietary-AGEs promoted neoplastic growth by functioning as ligand to RAGE expressed in the prostate tumor stroma not tumor epithelium. Dietary-AGE activation of stromal RAGE caused a regulatory program of ‘activated fibroblasts’ defined by the increased expression of cancer associated fibroblast markers, NFkB, MYC and pro-tumorigenic paracrine secretion. Fibroblast activation was accompanied by decreased expression of androgen receptor (AR) and the increased expression of neuroendocrine differentiation markers in tumor epithelial cells. AGE exposed primary fibroblasts isolated from patient tissue conferred tumor promoting abilities when cultured with patient matched tumor epithelial cells. Conclusions For the first time these data demonstrate a direct cause and effect relationship between dietary-AGEs and neoplastic growth. This may lay the foundation for strategic self-management strategies aimed at reducing AGE exposure in the diet to reduce cancer incidence and mortality. Funding Sources NIH/NCI; ACS.

Retraction Note: Critical role of CCDC6 in the neoplastic growth of testicular germ cell tumors

This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1186/1471-2407-13-433.

Dynamics of limited neoplastic growth on Pongamia pinnata (L.) (Fabaceae) leaf, induced by Aceria pongamiae (Acari: Eriophyidae)

Background Galls or the neoplastic growth on plants result from a complex type of interaction between the inducers (Acari, Insects, Microbes and Nematodes) and plants. The present study sheds light on the gall inducing habit of a highly host specific eriophyid mite, Aceria pongamiae, on the leaves of Pongamia pinnata leading to the production of abnormal pouch like outgrowths on the adaxial and abaxial surfaces of the foliage. Each leaf gall is a highly complex, irregular massive structure, and the formation of which often leads to complete destruction of leaves, especially during heavy mite infestation, and thereby adversely affecting the physiology and growth of the host plant. Results The study was carried out by making comparative observations on FE-SEM histological sections of galls representing four different growth stages categorized on the basis of difference in age groups. Apart from variations in cell metaplasia, a dramatic change was observed in the abaxial-adaxial polarity of the laminar surfaces also throughout the developmental sequence of galls, in all the four growth stages. Significant variations could be observed in the anti-oxidative potency as well as elemental composition in the all the four age groups of galls, and also revealed ATR-FTIR pattern of gall formation. Conclusion Being the first attempt to unravel the mystery of gall induction by eriophyids in general and by A. pongamiae in particular, on its host plant P.pinnata, by shedding light on the structural and histological alterations taking place during leaf gall formation under the influence of the mite, the current study is to be treated as the model of plant-animal interactive system.

Consumption of Dietary Advanced Glycation End Products Promotes Prostate Tumor Growth by Creating a Tumor Enhancing Stromal Microenvironment

Objectives The literature regarding the role of advanced glycation end products (AGEs) on tumor biology has shown only moderate promise reflected by increases in cell growth, migration and invasion in vitro which is not supported by increased tumor growth in vivo14-16– A caveat to these studies is that they are centered upon a single AGE peptide and a subsequent assessment of their molecular effects on tumor epithelial cells. The objective is to show that by feeding mice a high AGE diet we can recapitulate a microenvironment comprising of a wide spectrum of AGEs which can influence neoplastic growth. Methods We recapitulated a dietary-AGE induced microenvironment in syngeneic xenograft and spontaneous breast and prostate mouse cancer models and the effects on tumor growth assessed. The mechanistic consequences of dietary-AGEs on the tumor microenvironment were further defined using mouse and human primary and immortalized two-compartment co-culture ex vivo culture models. Results Dietary-AGE consumption in breast and prostate tumor models significantly accelerated tumor growth by functioning as ligand to the transmembrane receptor for AGE (RAGE). Our studies demonstrate that AGEs promote neoplastic growth by functioning as ligand to RAGE expressed in the tumor stroma not the tumor epithelial cells. Dietary-AGE activation of RAGE in both breast and prostate tumors caused a regulatory program of ‘activated fibroblasts’ defined by increased expression of cancer associated fibroblast markers, NFkB and MYC upregulation, and pro-tumorigenic paracrine secretion. Complementary to this, our published studies show that high intake of dietary AGE after BCa diagnosis increases risk of mortality in postmenopausal women. Conclusions These data demonstrate, for the first time, the oncogenic potential of dietary-AGEs in promoting neoplastic growth. This lays the foundation for strategic changes aimed at reducing cancer incidence and mortality as pharmacological, educational and/or interventional strategies aimed at reducing the dietary-AGE accumulation pool may one day be viewed as universal cancer preventative and/or therapeutic initiatives especially when combined with existing therapies. Funding Sources David P. Turner was supported by grants from the NIH/NCI, R21 CA194469 and U54 CA21096..