BBA - Reviews on Cancer (v.1775, #1)

A word of farewell and a word of welcome by Dennis Vance; Peter van der Vliet (1-2).

BBA in the year 2007 by Dennis E. Vance (3-4).

Cellular senescence and cancer treatment by Clemens A. Schmitt (5-20).
Cellular senescence, an irreversible cell-cycle arrest, reflects a safeguard program that limits the proliferative capacity of the cell exposed to endogenous or exogenous stress signals. A number of recent studies have clarified that an acutely inducible form of cellular senescence may act in response to oncogenic activation as a natural barrier to interrupt tumorigenesis at a premalignant level. Paralleling the increasing insights into premature senescence as a tumor suppressor mechanism, a growing line of evidence identifies cellular senescence as a critical effector program in response to DNA damaging chemotherapeutic agents. This review discusses molecular pathways to stress-induced senescence, the interference of a terminal arrest condition with clinical outcome, and the critical overlap between premature senescence and apoptosis as both tumor suppressive and drug-responsive cellular programs.
Keywords: Anticancer therapy; apoptosis; cellular senescence; DNA damage; mouse model; oncogene;

Transforming growth factor-β (TGF-β) is a secreted polypeptide that signals via receptor serine/threonine kinases and intracellular Smad effectors. TGF-β inhibits proliferation and induces apoptosis in various cell types, and accumulation of loss-of-function mutations in the TGF-β receptor or Smad genes classify the pathway as a tumor suppressor in humans. In addition, various oncogenic pathways directly inactivate the TGF-β receptor-Smad pathway, thus favoring tumor growth. On the other hand, all human tumors overproduce TGF-β whose autocrine and paracrine actions promote tumor cell invasiveness and metastasis. Accordingly, TGF-β induces epithelial–mesenchymal transition, a differentiation switch that is required for transitory invasiveness of carcinoma cells. Tumor-derived TGF-β acting on stromal fibroblasts remodels the tumor matrix and induces expression of mitogenic signals towards the carcinoma cells, and upon acting on endothelial cells and pericytes, TGF-β regulates angiogenesis. Finally, TGF-β suppresses proliferation and differentiation of lymphocytes including cytolytic T cells, natural killer cells and macrophages, thus preventing immune surveillance of the developing tumor. Current clinical approaches aim at establishing novel cancer drugs whose mechanisms target the TGF-β pathway. In conclusion, TGF-β signaling is intimately implicated in tumor development and contributes to all cardinal features of tumor cell biology.
Keywords: Cancer; Epithelial–mesenchymal transition; Metastasis; Smad; TGF-β; Tumor suppressor;

The LKB1 tumor suppressor kinase in human disease by Pekka Katajisto; Tea Vallenius; Kari Vaahtomeri; Niklas Ekman; Lina Udd; Marianne Tiainen; Tomi P. Mäkelä (63-75).
Inactivating germline mutations in the LKB1 gene underlie Peutz–Jeghers syndrome characterized by hamartomatous polyps and an elevated risk for cancer. Recent studies suggest the involvement of LKB1 also in more common human disorders including diabetes and in a significant fraction of lung adenocarcinomas. These observations have increased the interest towards signaling pathways of this tumor suppressor kinase. The recent breakthroughs in understanding the molecular functions of the LKB1 indicate its contribution as a regulator of cell polarity, energy metabolism and cell proliferation. Here we review how the substrates and cellular functions of LKB1 may be linked to Peutz–Jeghers syndrome and other diseases, and discuss how some of the molecular changes associated with altered LKB1 signaling might be used in therapeutic approaches.
Keywords: Peutz–Jeghers syndrome; LKB1; Polyp; Cancer; Energy metabolism; Polarity; Lung adenocarcinoma; Kinase;

Dual targeting of epigenetic therapy in cancer by Debby M.E.I. Hellebrekers; Arjan W. Griffioen; Manon van Engeland (76-91).
Aberrant epigenetic silencing of tumor suppressor genes by promoter DNA hypermethylation and histone deacetylation plays an important role in the pathogenesis of cancer. The potential reversibility of epigenetic abnormalities encouraged the development of pharmacologic inhibitors of DNA methylation and histone deacetylation as anti-cancer therapeutics. (Pre)clinical studies of DNA methyltransferase (DNMT) and histone deacetylase (HDAC) inhibitors have yielded encouraging results, especially against hematologic malignancies. Recently, several studies demonstrated that DNMT and HDAC inhibitors are also potent angiostatic agents, inhibiting (tumor) endothelial cells and angiogenesis in vitro and in vivo. By reactivation of epigenetically silenced tumor suppressor genes with angiogenesis inhibiting properties, DNMT and HDAC inhibitors might indirectly – via their effects on tumor cells – decrease tumor angiogenesis in vivo. However, this does not explain the direct angiostatic effects of these agents, which can be unraveled by gene expression studies and examination of epigenetic promoter modifications in endothelial cells treated with DNMT and HDAC inhibitors. Clearly, the dual targeting of epigenetic therapy on both tumor cells and tumor vasculature makes them attractive combinatorial anti-tumor therapeutics. Here we review the therapeutic potential of DNMT and HDAC inhibitors as anti-cancer drugs, as evaluated in clinical trials, and their angiostatic activities, apart from their inhibitory effects on tumor cells.
Keywords: DNA methyltransferase inhibitor; Histone deacetylase inhibitor; Anti-angiogenic therapy; Tumor angiogenesis; Epigenetic;

FoxM1: At the crossroads of ageing and cancer by Jamila Laoukili; Marie Stahl; René H. Medema (92-102).
Forkhead transcription factors are intimately involved in the regulation of organismal development, cell differentiation and proliferation. Here we review the current knowledge of the role played by FoxM1 in these various processes. This particular member of the Forkhead family is broadly expressed in actively dividing cells and is crucial for cell cycle-dependent gene expression in the G2 phase of the cell cycle. FoxM1 plays a crucial role in insuring the fidelity of the cell division process, as inhibition of FoxM1 activity results in serious aberrancies during mitosis, such as frequent chromosome missegregation, defects in cytokinesis and overt aneuploidy. FoxM1 expression also appears to be tightly correlated with the proliferative rate of a cell. For example, FoxM1 is one of the most significantly down-regulated genes in prematurely aged human fibroblasts (Progeria syndrome), while elevated expression of FoxM1 is seen in most human carcinomas. These observations suggest that interference with FoxM1 activity may contribute to the increase in mitotic errors seen in human diseases such as cancer and early onset of ageing diseases. In this review, several aspects of FoxM1 function will be discussed, as well as their implication in tumorigenesis.
Keywords: Cell cycle; Transcriptional regulation; Mitosis; Checkpoints; Forkhead;

Expression and genomic profiling of colorectal cancer by J. Cardoso; J. Boer; H. Morreau; R. Fodde (103-137).
Colorectal cancer still represents a paradigm for the elucidation of the cellular, genetic and molecular mechanisms that underly solid tumor initiation, progression to malignancy, and metastasis to distal organ sites. The relative ease with which pathological specimens can be obtained by either surgery or endoscopy from different stages of tumor progression has facilitated the application of omics technologies to allow the genome-wide analysis both at the RNA (gene expression) and DNA (aneuploidy) levels. Here, we have reviewed the multiplicity of studies appeared to date in the scientific literature on the expression and genomic analysis of colorectal cancer, and attempted an integration of the profiling data generated and made available in the public domain. This approach is likely to pinpoint specific chromosomal loci and the corresponding genes which (i) play rate-limiting roles in colorectal cancer, (ii) represent putative diagnostic and prognostic markers for the accurate prediction of clinical outcome and response to treatment, and (iii) encompass potential therapeutic targets. Moreover, cross-species data mining and integration of the human colorectal cancer profiles with those obtained from mouse models of intestinal tumorigenesis will even more contribute to the elucidation of highly conserved pathways and cellular functions underlying malignancy in the GI tract. Notwithstanding the above promises, tumor heterogeneity, limited cohort sizes, and methodological differences among experimental and bioinformatic approaches still poses main obstacles towards the optimal utilization and integration of omics profiles.
Keywords: Colorectal cancer; Expression profiling; Genomic profiling; Array CGH; Genomics; Adenoma; Carcinoma; Metastasis;

DNA hypomethylation and human diseases by Ann S. Wilson; Barbara E. Power; Peter L. Molloy (138-162).
Changes in human DNA methylation patterns are an important feature of cancer development and progression and a potential role in other conditions such as atherosclerosis and autoimmune diseases (e.g., multiple sclerosis and lupus) is being recognised. The cancer genome is frequently characterised by hypermethylation of specific genes concurrently with an overall decrease in the level of 5 methyl cytosine. This hypomethylation of the genome largely affects the intergenic and intronic regions of the DNA, particularly repeat sequences and transposable elements, and is believed to result in chromosomal instability and increased mutation events. This review examines our understanding of the patterns of cancer-associated hypomethylation, and how recent advances in understanding of chromatin biology may help elucidate the mechanisms underlying repeat sequence demethylation. It also considers how global demethylation of repeat sequences including transposable elements and the site-specific hypomethylation of certain genes might contribute to the deleterious effects that ultimately result in the initiation and progression of cancer and other diseases. The use of hypomethylation of interspersed repeat sequences and genes as potential biomarkers in the early detection of tumors and their prognostic use in monitoring disease progression are also examined.
Keywords: DNA hypomethylation; Global demethylation; Cancer; Biomarker; Transposable element; Repeat sequence;

Signalling via integrins: Implications for cell survival and anticancer strategies by Stephanie Hehlgans; Michael Haase; Nils Cordes (163-180).
Integrin-associated signalling renders cells more resistant to genotoxic anti-cancer agents like ionizing radiation and chemotherapeutic substances, a phenomenon termed cell adhesion-mediated radioresistance/drug resistance (CAM-RR, CAM-DR). Integrins are heterodimeric cell-surface molecules that on one side link the actin cytoskeleton to the cell membrane and on the other side mediate cell–matrix interactions. In addition to their structural functions, integrins mediate signalling from the extracellular space into the cell through integrin-associated signalling and adaptor molecules such as FAK (focal adhesion kinase), ILK (integrin-linked kinase), PINCH (particularly interesting new cysteine-histidine rich protein) and Nck2 (non-catalytic (region of) tyrosine kinase adaptor protein 2). Via these molecules, integrin signalling tightly and cooperatively interacts with receptor tyrosine kinase signalling to regulate survival, proliferation and cell shape as well as polarity, adhesion, migration and differentiation. In tumour cells of diverse origin like breast, colon or skin, the function and regulation of these molecules is partly disturbed and thus might contribute to the malignant phenotype and pre-existent and acquired multidrug resistance. These issues as well as a variety of therapeutic options envisioned to influence tumour cell growth, metastasis and resistance, including kinase inhibitors, anti-integrin antibodies or RNA interference, will be summarized and discussed in this review.
Keywords: ECM; FAK; ILK; Integrin; Nck2; PINCH;

Circulating nucleic acids (CNAs) and cancer—A survey by M. Fleischhacker; B. Schmidt (181-232).
It has been known for decades that it is possible to detect small amounts of extracellular nucleic acids in plasma and serum of healthy and diseased human beings. The unequivocal proof that part of these circulating nucleic acids (CNAs) is of tumor origin, initiated a surge of studies which confirmed and extended the original observations. In the past few years many experiments showed that tumor-associated alterations can be detected at the DNA and RNA level. At the DNA level the detection of point mutations, microsatellite alterations, chromosomal alterations, i.e. inversion and deletion, and hypermethylation of promoter sequences were demonstrated. At the RNA level the overexpression of tumor-associated genes was shown. These observations laid the foundation for the development of assays for an early detection of cancer as well as for other clinical means.
Keywords: Circulating nucleic acids; DNA; RNA; Plasma; Cancer; Review;