High-Fat Diet Induced PPARδ Promotes Self-renewal of Preleukemic Progenitors in Development of Acute Promyelocytic Leukemia.

From risk association between acute promyelocytic leukemia (APL) and obese-overweight individuals, Mazzarella and colleagues hypothesized that a high-fat diet (HFD) promotes development of APL. Using mouse APL model (PML-RARα knock-in), the authors demonstrated that linoleic acid drives activation of PPARδ in hematopoietic progenitors, and that activation of PPARδ increases proliferation of progenitor cells with PML-RARA expression toward APL. Involvements of PPARδ on regulation of stem cell renewal and proliferation were shown in colorectal cancers earlier, but this study newly demonstrates in hematopoietic progenitors, while suggesting use of diet rich in linoleic acid with caution. See related article by Mazzarella et al., p. 59.

Molecular disparities in colorectal cancers of White Americans, Alabama African Americans, and Oklahoma American Indians.

In the US, the majority of cancer samples analyzed are from white people, leading to biases in racial and ethnic treatment outcomes. Colorectal cancer (CRC) incidence and mortality rates are high in Alabama African Americans (AAs) and Oklahoma American Indians (AIs). We hypothesized that differences between racial groups may partially explain these disparities. Thus, we compared transcriptomic profiles of CRCs of Alabama AAs, Oklahoma AIs, and white people from both states. Compared to CRCs of white people, CRCs of AAs showed (a) higher expression of cytokines and vesicle trafficking toward modulated antitumor-immune activity, and (b) lower expression of the ID1/BMP/SMAD axis, IL22RA1, APOBEC3, and Mucins; and AIs had (c) higher expression of PTGS2/COX2 (an NSAID target/pro-oncogenic inflammation) and splicing regulators, and (d) lower tumor suppressor activities (e.g., TOB2, PCGF2, BAP1). Therefore, targeting strategies designed for white CRC patients may be less effective for AAs/AIs. These findings illustrate needs to develop optimized interventions to overcome racial CRC disparities.

Pancreatic Cancer Disparities among Gender, Race, and Ethnicity: The PRECEDE Consortium Outcomes and Impact.

The Pancreatic Cancer Early Detection (PRECEDE) Consortium was launched internationally to assess the surveillance of high-risk individuals (HRI) of pancreatic cancer, focusing on genetic risk factors. In the early recruitment period of 3 years from May 2020 to March 2022, the PRECEDE gathered analysis-eligible data on 1,113 HRIs. In this issue of Cancer Prevention Research, Katona and colleagues reported current portrait of demographics of the participants, with significant disparities in gender, race and ethnicity. Now the PRECEDE Consortium aims at correcting these disparities in the next 3 years and double the percentage of underrepresented groups to more closely represent the demographics of patients. See related article by Katona et al., p. 343.

Genomic instability genes in lung and colon adenocarcinoma indicate organ specificity of transcriptomic impact on Copy Number Alterations.

Genomic instability (GI) in cancer facilitates cancer evolution and is an exploitable target for therapy purposes. However, specific genes involved in cancer GI remain elusive. Causal genes for GI via expressions have not been comprehensively identified in colorectal cancers (CRCs). To fill the gap in knowledge, we developed a data mining strategy (Gene Expression to Copy Number Alterations; "GE-CNA"). Here we applied the GE-CNA approach to 592 TCGA CRC datasets, and identified 500 genes whose expression levels associate with CNA. Among these, 18 were survival-critical (i.e., expression levels correlate with significant differences in patients' survival). Comparison with previous results indicated striking differences between lung adenocarcinoma and CRC: (a) less involvement of overexpression of mitotic genes in generating genomic instability in the colon and (b) the presence of CNA-suppressing pathways, including immune-surveillance, was only partly similar to those in the lung. Following 13 genes (TIGD6, TMED6, APOBEC3D, EP400NL, B3GNT4, ZNF683, FOXD4, FOXD4L1, PKIB, DDB2, MT1G, CLCN3, CAPS) were evaluated as potential drug development targets (hazard ratio [> 1.3 or < 0.5]). Identification of specific CRC genomic instability genes enables researchers to develop GI targeting approach. The new results suggest that the "targeting genomic instability and/or aneuploidy" approach must be tailored for specific organs.

Survival-Critical Genes Associated with Copy Number Alterations in Lung Adenocarcinoma.

Chromosome Instability (CIN) in tumors affects carcinogenesis, drug resistance, and recurrence/prognosis. Thus, it has a high impact on outcomes in clinic. However, how CIN occurs in human tumors remains elusive. Although cells with CIN (i.e., pre/early cancer cells) are proposed to be removed by apoptosis and/or a surveillance mechanism, this surveillance mechanism is poorly understood. Here we employed a novel data-mining strategy (Gene Expression to Copy Number Alterations [CNA]; "GE-CNA") to comprehensively identify 1578 genes that associate with CIN, indicated by genomic CNA as its surrogate marker, in human lung adenocarcinoma. We found that (a) amplification/insertion CNA is facilitated by over-expressions of DNA replication stressor and suppressed by a broad range of immune cells (T-, B-, NK-cells, leukocytes), and (b) deletion CNA is facilitated by over-expressions of mitotic regulator genes and suppressed predominantly by leukocytes guided by leukocyte extravasation signaling. Among the 39 CNA- and survival-associated genes, the purine metabolism (PPAT, PAICS), immune-regulating CD4-LCK-MEC2C and CCL14-CCR1 axes, and ALOX5 emerged as survival-critical pathways. These findings revealed a broad role of the immune system in suppressing CIN/CNA and cancer development in lung, and identified components representing potential targets for future chemotherapy, chemoprevention, and immunomodulation approaches for lung adenocarcinoma.

GSK3-ARC/Arg3.1 and GSK3-Wnt signaling axes trigger amyloid-ß accumulation and neuroinflammation in middle-aged Shugoshin 1 mice.

The cerebral amyloid-ß accumulation that begins in middle age is considered the critical triggering event in the pathogenesis of late-onset Alzheimer's disease (LOAD). However, the molecular mechanism remains elusive. The Shugoshin 1 (Sgo1-/+ ) mouse model, a model for mitotic cohesinopathy-genomic instability that is observed in human AD at a higher rate, showed spontaneous accumulation of amyloid-ß in the brain at old age. With the model, novel insights into the molecular mechanism of LOAD development are anticipated. In this study, the initial appearance of cerebral amyloid-ß accumulation was determined as 15-18 months of age (late middle age) in the Sgo1-/+ model. The amyloid-ß accumulation was associated with unexpected GSK3α/ß inactivation, Wnt signaling activation, and ARC/Arg3.1 accumulation, suggesting involvement of both the GSK3-Arc/Arg3.1 axis and the GSK3-Wnt axis. As observed in human AD brains, neuroinflammation with IFN-γ expression occurred with amyloid-ß accumulation and was pronounced in the aged (24-month-old) Sgo1-/+ model mice. AD-relevant protein panels (oxidative stress defense, mitochondrial energy metabolism, and ß-oxidation and peroxisome) analysis indicated (a) early increases in Pdk1 and Phb in middle-aged Sgo1-/+ brains, and (b) misregulations in 32 proteins among 130 proteins tested in old age. Thus, initial amyloid-ß accumulation in the Sgo1-/+ model is suggested to be triggered by GSK3 inactivation and the resulting Wnt activation and ARC/Arg3.1 accumulation. The model displayed characteristics and affected pathways similar to those of human LOAD including neuroinflammation, demonstrating its potential as a study tool for the LOAD development mechanism and for preclinical AD drug research and development.

"Amyloid-beta accumulation cycle" as a prevention and/or therapy target for Alzheimer's disease.

The cell cycle and its regulators are validated targets for cancer drugs. Reagents that target cells in a specific cell cycle phase (e.g., antimitotics or DNA synthesis inhibitors/replication stress inducers) have demonstrated success as broad-spectrum anticancer drugs. Cyclin-dependent kinases (CDKs) are drivers of cell cycle transitions. A CDK inhibitor, flavopiridol/alvocidib, is an FDA-approved drug for acute myeloid leukemia. Alzheimer's disease (AD) is another serious issue in contemporary medicine. The cause of AD remains elusive, although a critical role of latent amyloid-beta accumulation has emerged. Existing AD drug research and development targets include amyloid, amyloid metabolism/catabolism, tau, inflammation, cholesterol, the cholinergic system, and other neurotransmitters. However, none have been validated as therapeutically effective targets. Recent reports from AD-omics and preclinical animal models provided data supporting the long-standing notion that cell cycle progression and/or mitosis may be a valid target for AD prevention and/or therapy. This review will summarize the recent developments in AD research: (a) Mitotic re-entry, leading to the "amyloid-beta accumulation cycle," may be a prerequisite for amyloid-beta accumulation and AD pathology development; (b) AD-associated pathogens can cause cell cycle errors; (c) thirteen among 37 human AD genetic risk genes may be functionally involved in the cell cycle and/or mitosis; and (d) preclinical AD mouse models treated with CDK inhibitor showed improvements in cognitive/behavioral symptoms. If the "amyloid-beta accumulation cycle is an AD drug target" concept is proven, repurposing of cancer drugs may emerge as a new, fast-track approach for AD management in the clinic setting.

Critical role of mitosis in spontaneous late-onset Alzheimer's disease; from a Shugoshin 1 cohesinopathy mouse model.

From early-onset Alzheimer's disease (EOAD) studies, the amyloid-beta hypothesis emerged as the foremost theory of the pathological causes of AD. However, how amyloid-beta accumulation is triggered and progresses toward senile plaques in spontaneous late-onset Alzheimer's disease (LOAD) in humans remains unanswered. Various LOAD facilitators have been proposed, and LOAD is currently considered a complex disease with multiple causes. Mice do not normally develop LOAD. Possibly due to the multiple causes, proposed LOAD facilitators have not been able to replicate spontaneous LOAD in mice, representing a disease modeling issue. Recently, we reported spontaneous late-onset development of amyloid-beta accumulation in brains of Shugoshin 1 (Sgo1) haploinsufficient mice, a cohesinopathy-mediated chromosome instability model. The result for the first time expands disease relevance of mitosis studies to a major disease other than cancers. Reverse-engineering of the model would shed light on the process of late-onset amyloid-beta accumulation in the brain and spontaneous LOAD development, and contribute to development of interventions for LOAD. This review will discuss the Sgo1 model, our current "three-hit hypothesis" regarding LOAD development with an emphasis on critical role of prolonged mitosis in amyloid-beta accumulation, and implications for human LOAD intervention and treatment. Abbreviations: Alzheimer's disease (AD); Late-onset Alzheimer's disease (LOAD); Early-onset Alzheimer's disease (EOAD); Shugoshin-1 (Sgo1); Chromosome Instability (CIN); apolipoprotein (Apoe); Central nervous system (CNS); Amyloid precursor protein (APP); N-methyl-d-aspartate (NMDA); Hazard ratio (HR); Cyclin-dependent kinase (CDK); Chronic Atrial Intestinal Dysrhythmia (CAID); beta-secretase 1 (BACE); phosphor-Histone H3 (p-H3); Research and development (R&D); Non-steroidal anti-inflammatory drugs (NSAIDs); Brain blood barrier (BBB).

Spontaneous development of Alzheimer's disease-associated brain pathology in a Shugoshin-1 mouse cohesinopathy model.

Spontaneous late-onset Alzheimer's disease (LOAD) accounts for more than 95% of all human AD. As mice do not normally develop AD and as understanding on molecular processes leading to spontaneous LOAD has been insufficient to successfully model LOAD in mouse, no mouse model for LOAD has been available. Existing mouse AD models are all early-onset AD (EOAD) models that rely on forcible expression of AD-associated protein(s), which may not recapitulate prerequisites for spontaneous LOAD. This limitation in AD modeling may contribute to the high failure rate of AD drugs in clinical trials. In this study, we hypothesized that genomic instability facilitates development of LOAD and tested two genomic instability mice models in the brain pathology at the old age. Shugoshin-1 (Sgo1) haploinsufficient (∓) mice, a model of chromosome instability (CIN) with chromosomal and centrosomal cohesinopathy, spontaneously exhibited a major feature of AD pathology; amyloid beta accumulation that colocalized with phosphorylated Tau, beta-secretase 1 (BACE), and mitotic marker phospho-Histone H3 (p-H3) in the brain. Another CIN model, spindle checkpoint-defective BubR1-/+ haploinsufficient mice, did not exhibit the pathology at the same age, suggesting the prolonged mitosis-origin of the AD pathology. RNA-seq identified ten differentially expressed genes, among which seven genes have indicated association with AD pathology or neuronal functions (e.g., ARC, EBF3). Thus, the model represents a novel model that recapitulates spontaneous LOAD pathology in mouse. The Sgo1-/+ mouse may serve as a novel tool for investigating mechanisms of spontaneous progression of LOAD pathology, for early diagnosis markers, and for drug development.

Biological effects and epidemiological consequences of arsenic exposure, and reagents that can ameliorate arsenic damage in vivo.

Through contaminated diet, water, and other forms of environmental exposure, arsenic affects human health. There are many U.S. and worldwide "hot spots" where the arsenic level in public water exceeds the maximum exposure limit. The biological effects of chronic arsenic exposure include generation of reactive oxygen species (ROS), leading to oxidative stress and DNA damage, epigenetic DNA modification, induction of genomic instability, and inflammation and immunomodulation, all of which can initiate carcinogenesis. High arsenic exposure is epidemiologically associated with skin, lung, bladder, liver, kidney and pancreatic cancer, and cardiovascular, neuronal, and other diseases. This review briefly summarizes the biological effects of arsenic exposure and epidemiological cancer studies worldwide, and provides an overview for emerging rodent-based studies of reagents that can ameliorate the effects of arsenic exposure in vivo. These reagents may be translated to human populations for disease prevention. We propose the importance of developing a biomarker-based precision prevention approach for the health issues associated with arsenic exposure that affects millions of people worldwide.

Frequently mutated genes/pathways and genomic instability as prevention targets in liver cancer.

The incidence of liver cancer has increased in recent years. Worldwide, liver cancer is common: more than 600000 related deaths are estimated each year. In the USA, about 27170 deaths due to liver cancer are estimated for 2016. Liver cancer is highly resistant to conventional chemotherapy and radiotherapy. For all stages combined, the 5-year survival rate is 15-17%, leaving much to be desired for liver cancer prevention and therapy. Heterogeneity, which can originate from genomic instability, is one reason for poor outcome. About 80-90% of liver cancers are hepatocellular carcinoma (HCC), and recent cancer genome sequencing studies have revealed frequently mutated genes in HCC. In this review, we discuss the cause of the tumor heterogeneity based on the functions of genes that are frequently mutated in HCC. We overview the functions of the genes that are most frequently mutated (e.g. TP53, CTNNB1, AXIN1, ARID1A and WWP1) that portray major pathways leading to HCC and identify the roles of these genes in preventing genomic instability. Notably, the pathway analysis suggested that oxidative stress management may be critical to prevent accumulation of DNA damage and further mutations. We propose that both chromosome instability (CIN) and microsatellite instability (MIN) are integral to the hepatic carcinogenesis process leading to heterogeneity in HCC and that the pathways leading to heterogeneity may be targeted for prognosis, prevention and treatment.

Emerging links among Chromosome Instability (CIN), cancer, and aging.

Aneuploidy was predicted to cause cancer. To test the prediction, various Chromosome Instability (CIN) mice models that carry transgenic mutations in mitotic regulators have been created. The availability of these mice has aided researchers in discovering connections between CIN, cancer, and aging. This review will focus on recent interdisciplinary findings regarding how CIN and aneuploidy affect carcinogenesis, immune dysfunction, and aging. High CIN can be generated in vivo by various intrinsic alterations (e.g., gene mutation, epigenetic modification) and extrinsic/environmental challenges (e.g., biological, chemical, biophysical), while immune surveillance, cell death, and natural turnover can remove cells with CIN. CIN itself is mutagenic and may cause further cellular mutations, which can be carcinogenic. Mitotically damaged cells can activate senescence-related tumor suppressors (e.g., p21WAF1 , p27KIP1 , p16INK4A ), which may lead to tissue-level senescence/aging through inflammatory paracrine mechanisms called Senescence-Associated Secretory Phenotype (SASP) and Senescence Inflammatory Response (SIR). Organs with high CIN show altered gene expressions in both organ-specific and non-specific manners. Organ-specific gene expression signatures include activation of oncogenic pathways. Non-organ-specific gene expression signatures include metabolic changes and downregulations in immune functions. Immune surveillance normally targets senescent cells and tetraploid cells, a form of aneuploidy, for elimination. However, with partial immune dysfunction, immune surveillance is weakened with systemic CIN. In this case, more senescent cells and aneuploid cells survive, which further leads to an inflammatory, pro-tumorigenic, and senescent/aging microenvironment. We also discuss how we may intervene in this sequence of events to prevent CIN- or age-related carcinogenesis and/or some aspects of tissue aging. © 2016 Wiley Periodicals, Inc.

Systemic Chromosome Instability Resulted in Colonic Transcriptomic Changes in Metabolic, Proliferation, and Stem Cell Regulators in Sgo1-/+ Mice.

Colon cancer is the second most lethal cancer and is predicted to claim 49,700 lives in the United States this year. Chromosome instability (CIN) is observed in 80% to 90% of colon cancers and is thought to contribute to colon cancer progression and recurrence. To investigate the impact of CIN on colon cancer development, we developed shugoshin-1 (Sgo1) haploinsufficient (-/+) mice, an animal model focusing on mitotic error-induced CIN. In this study, we analyzed signature changes in the colonic transcriptome of Sgo1(-/+) mice to examine the molecular events underlying the altered carcinogenesis profiles in Sgo1(-/+) mice. We performed next-generation sequencing of normal-looking colonic mucosal tissue from mice treated with the carcinogen azoxymethane after 24 weeks. Transcriptome profiling revealed 349 hits with a 2-fold expression difference threshold (217 upregulated genes, 132 downregulated genes, P < 0.05). Pathway analyses indicated that the Sgo1-CIN tissues upregulated pathways known to be activated in colon cancer, including lipid metabolism (z score 4.47), Notch signaling (4.47), insulin signaling (3.81), and PPAR pathways (3.75), and downregulated pathways involved in immune responses including allograft rejection (6.69) and graft-versus-host disease (6.54). Notably, stem cell markers were also misregulated. Collectively, our findings demonstrate that systemic CIN results in transcriptomic changes in metabolism, proliferation, cell fate, and immune responses in the colon, which may foster a microenvironment amenable to cancer development. Therefore, therapeutic approaches focusing on these identified pathways may be valuable for colon cancer prevention and treatment.

Antagonizing pathways leading to differential dynamics in colon carcinogenesis in Shugoshin1 (Sgo1)-haploinsufficient chromosome instability model.

Colon cancer is the second most lethal cancer. It is predicted to claim 50,310 lives in 2014. Chromosome Instability (CIN) is observed in 80-90% of colon cancers, and is thought to contribute to colon cancer progression and recurrence. However, there are no animal models of CIN that have been validated for studies of colon cancer development or drug testing. In this study, we sought to validate a mitotic error-induced CIN model mouse, the Shugoshin1 (Sgo1) haploinsufficient mouse, as a colon cancer study model. Wild-type and Sgo1(-/+) mice were treated with the colonic carcinogen, azoxymethane (AOM). We tracked colon tumor development 12, 24, and 36 wk after treatment to assess progression of colon tumorigenesis. Initially, more precancerous lesions, Aberrant Crypt Foci (ACF), developed in Sgo1(-/+) mice. However, the ACF did not develop straightforwardly into larger tumors. At the 36-wk endpoint, the number of gross tumors in Sgo1(-/+) mice was no different from that in wild-type controls. However, Copy Number Variation (CNV) analysis indicated that fully developed colon tumor in Sgo1(-/+) mice carried 13.75 times more CNV. Immunohistological analyses indicated that Sgo1(-/+) mice differentially expressed IL-6, Bcl2, and p16(INK4A) . We propose that formation of ACF in Sgo1(-/+) mice is facilitated by the IL6-STAT3-SOCS3 oncogenic pathway and by the Bcl2-anti-apoptotic pathway, yet further development of the ACF to tumors is inhibited by the p16(INK4A) tumor suppressor pathway. Manipulating these pathways would be beneficial for inhibiting development of colon cancer with CIN.

Targeting pancreatitis blocks tumor-initiating stem cells and pancreatic cancer progression.

Recent development of genetically engineered mouse models (GEMs) for pancreatic cancer (PC) that recapitulates human disease progression has helped to identify new strategies to delay/inhibit PC development. We first found that expression of the pancreatic tumor-initiating/cancer stem cells (CSC) marker DclK1 occurs in early stage PC and in both early and late pancreatic intraepithelial neoplasia (PanIN) and that it increases as disease progresses in GEM and also in human PC. Genome-wide next generation sequencing of pancreatic ductal adenocarcinoma (PDAC) from GEM mice revealed significantly increased DclK1 along with inflammatory genes. Genetic ablation of cyclo-oxygenase-2 (COX-2) decreased DclK1 in GEM. Induction of inflammation/pancreatitis with cerulein in GEM mice increased DclK1, and the novel dual COX/5-lipoxygenase (5-LOX) inhibitor licofelone reduced it. Dietary licofelone significantly inhibited the incidence of PDAC and carcinoma in situ with significant inhibition of pancreatic CSCs. Licofelone suppressed pancreatic tumor COX-2 and 5-LOX activities and modulated miRNAs characteristic of CSC and inflammation in correlation with PDAC inhibition. These results offer a preclinical proof of concept to target the inflammation initiation to inhibit cancer stem cells early for improving the treatment of pancreatic cancers, with immediate clinical implications for repositioning dual COX/5-LOX inhibitors in human trials for high risk patients.

Tumor-promoting/progressing role of additional chromosome instability in hepatic carcinogenesis in Sgo1 (Shugoshin 1) haploinsufficient mice.

A major etiological risk factor for hepatocellular carcinoma (HCC) is infection by Hepatitis viruses, especially hepatitis B virus and hepatitis C virus. Hepatitis B virus and hepatitis C virus do not cause aggressive activation of an oncogenic pathway, but they transactivate a broad array of genes, cause chronic inflammation, and, through interference with mitotic processes, lead to mitotic error-induced chromosome instability (ME-CIN). However, how ME-CIN is involved in the development of HCC remains unclear. Delineating the effect of ME-CIN on HCC development should help in identifying measures to combat HCC. In this study, we used ME-CIN model mice haploinsufficient in Shugoshin 1 (Sgo1(-/+)) to assess the role of ME-CIN in HCC development. Treatment with the carcinogen azoxymethane caused Sgo1(-/+) ME-CIN model mice to develop HCCs within 6 months, whereas control mice developed no HCC (P < 0.003). The HCC development was associated with expression of early HCC markers (glutamine synthetase, glypican 3, heat shock protein 70, and the serum marker alpha fetoprotein), although without fibrosis. ME-CIN preceded the expression of HCC markers, suggesting that ME-CIN is an important early event in HCC development. In 12-month-old untreated Sgo1 mice, persistent DNA damage, altered gene expression, and spontaneous HCCs were observed. Sgo1 protein accumulated in response to DNA damage in vitro. Overall, Sgo1(-/+)-mediated ME-CIN strongly promoted/progressed development of HCC in the presence of an initiator carcinogen, and it had a mild initiator effect by itself. Use of the ME-CIN model mice should help in identifying drugs to counteract the effects of ME-CIN and should accelerate anti-HCC drug development.

Genomic instability and colon carcinogenesis: from the perspective of genes.

Colon cancer is the second most lethal cancer; approximately 600,000 people die of it annually in the world. Colon carcinogenesis generally follows a slow and stepwise process of accumulation of mutations under the influence of environmental and epigenetic factors. To adopt a personalized (tailored) cancer therapy approach and to improve current strategies for prevention, diagnosis, prognosis, and therapy overall, advanced understanding of molecular events associated with colon carcinogenesis is necessary. A contemporary approach that combines genetics, epigenomics, and signaling pathways has revealed many genetic/genomic alterations associated with colon cancer progression and their relationships to a genomic instability phenotype prevalent in colon cancer. In this review, we describe the relationship between gene mutations associated with colon carcinogenesis and a genomic instability phenotype, and we discuss possible clinical applications of genomic instability studies. Colon carcinogenesis is associated with frequent mutations in several pathways that include phosphatidylinositol 3-kinase, adenomatous polyposis coli, p53 (TP53), F-box and WD repeat domain containing 7, transforming growth factor-ß, chromosome cohesion, and K-RAS. These genes frequently mutated in pathways affecting colon cancer were designated colon cancer (CAN) genes. Aberrations in major colon CAN genes have a causal relationship to genomic instability. Conversely, genomic instability itself plays a role in colon carcinogenesis in experimental settings, as demonstrated in transgenic mouse models with high genomic instability. Thus, there is a feedback-type relationship between CAN gene mutations and genomic instability. These genetic/genomic studies have led to emerging efforts to apply the knowledge to colon cancer prognosis and to targeted therapy.

Mitosis-targeting natural products for cancer prevention and therapy.

Mitosis is a complex process resulting in division of a cell into two daughter cells, and its failure often results in the death of the daughter cells (via apoptotic, necrotic, or proliferative/senescent death). Many chemicals that inhibit the mitotic process (anti-mitotic drugs) have proven effective for killing cancer cells in vitro and in clinical settings. Among the most studied anti-mitotic drugs are plant-origin natural products including taxanes (e.g. paclitaxel, docetaxel) and vinca alkaloids (e.g. vincristine, vinblastine), whose validated target is the spindle microtubules. With the success of these agents, efforts have been made to develop other spindle poisons as well as to improve efficacy of existing spindle poisons with structural modifications. Novel drugs and natural products that inhibit other proteins involved in mitosis (nonmicrotubule targets) have been sought in hopes of expanding available cancer-directed therapies. Recently, significant advances have been made in the understanding of mitotic mechanisms in tumor cells as well as in normal epithelial cells. These advances help us to identify and develop potential natural agents for the prevention and treatment of cancer. This review will focus on natural products that target mitotic process and/or proteins involved in mitotic progression.

Haploinsufficiency of SGO1 results in deregulated centrosome dynamics, enhanced chromosomal instability and colon tumorigenesis.

Chromosome instability (CIN) is found in 85% of colorectal cancers. Defects in mitotic processes are implicated in high CIN and may be critical events in colorectal tumorigenesis. Shugoshin-1 (SGO1) aids in the maintenance of chromosome cohesion and prevents premature chromosome separation and CIN. In addition, integrity of the centrosome may be compromised due to the deficiency of Cohesin and Sgo1 through the disengagement of centrioles. We report here the generation and characterization of SGO1-mutant mice and show that haploinsufficiency of SGO1 leads to enhanced colonic tumorigenesis. Complete disruption of SGO1 results in embryonic lethality, whereas SGO1+/- mice are viable and fertile. Haploinsufficiency of SGO1 results in genomic instability manifested as missegregation of chromosomes and formation of extra centrosomal foci in both murine embryonic fibroblasts and adult bone marrow cells. Enhanced CIN observed in SGO1-deficient mice resulted in an increase in formation of aberrant crypt foci (ACF) and accelerated development of tumors after exposure to azoxymethane (AOM), a colon carcinogen. Together, these results suggest that haploinsufficiency of SGO1 causes enhanced CIN, colonic preneoplastic lesions and tumorigenesis in mice. SGO1 is essential for the suppression of CIN and tumor formation.