Causality and Chance in the Development of Cancer

The methylation signature of hepatocellular carcinoma trajectory based on pseudotime and chronological time for predicting precancerous patients

BACKGROUND

Early screening of hepatocellular carcinoma (HCC) is strongly recommended for hepatitis B virus (HBV)-infected patients. We aimed to develop and validate a predictive nomogram based on HCC occurrence trajectory for screening precancerous patients with HCC.

METHODS

Peripheral blood mononuclear cells (PBMC) samples from 22 patients with HCC with their precancerous stage (n = 55) and 18 healthy controls were measured using HumanMethylation EPIC BeadChip assay. HCC trajectory was assessed by pseudotime based on TimeAx algorithm and chronological time. The 43 candidate CpG sites were selected from the methylation signature and measured using multiplex bisulfite sequencing in a retrospective cohort of HBV-infected patients (n = 604). A 5-CpG-classifier was built using the LASSO Cox regression model, based on the association between the methylation level of every CpG and the duration from enrollment to HCC occurrence of individual patient. We validated the risk stratification and predictive accuracy of this classifier in both the primary cohort (n = 300) and independent validation cohort (n = 304).

RESULTS

Pseudotime and chronological time of HCC trajectory analysis revealed that the PD-1/PD-L1 pathway underwent changes in the precancerous stage. Based on the trajectory of methylation signature, we built a 5-CpG-classifier which remained powerful and independent predictive efficiency after stratified analysis by clinicopathological risk factors in both primary cohort and independent validation cohort. A predicting nomogram including the 5-CpG-classifier was constructed after multivariate analysis. One-year cumulative hazard of HCC in low- and high-risk groups of HBV-infected patients was 3.0% (0.1%-5.8%) and 17.90% (11.00%-24.3%) (P < .0001) in primary cohort, 4.5% (1.20%-7.80%) and 27.3 (18.90-34.90) (P < .0001) in the independent validation cohort.

CONCLUSIONS

One-year before HCC was a critical period of transitional time when parts of the methylation profile underwent shifting toward HCC like. The nomogram could identify precancerous stage patients with HCC who should be screened for early diagnosis and intervention.

Founder pathogenic variants in colorectal neoplasia susceptibility genes in Ashkenazi Jews undergoing colonoscopy

BACKGROUND

Colorectal neoplasia is one of the most common tumors affecting Western populations.

METHODS

In this study we used a custom amplicon sequencing platform and an in-house bioinformatic pipeline to study constitutional DNA from two different case series of Ashkenazi Jews undergoing colonoscopy (n = 765). The first series all had pathologically confirmed colorectal adenomas and/or carcinoma. The second series consisted of persons who had undergone a colonoscopy within the five years prior to ascertainment, regardless of findings. Ninety-one percent of all patients were asymptomatic at the time of colonoscopy.

RESULTS

In the first group (n = 438), we identified 65 founder variants (56 in APC, 2 in GREM1, 3 in MSH2 and 4 in BLM). In the second group (n = 327), the findings were 30, nothing, 1 and 1, respectively, as well as 2 MSH6 variants.

CONCLUSIONS

Overall, we found that 10 to 15% of Ashkenazi Jewish persons undergoing colonoscopy harbor variants of interest in colorectal and/or polyposis predisposition. This includes pathogenic variants in MSH6, which is associated with colorectal cancer but not with polyposis. We identified no pathogenic variants in more recently discovered polyposis predisposition genes (POLE, POLD1 or NTHL1), rendering the presence of such founder variants rare.

The preimplantation genetic testing for monogenic disorders strategy for blocking the transmission of hereditary cancers through haplotype linkage analysis by karyomapping

PURPOSE

Providing feasible preimplantation genetic testing strategies for monogenic disorders (PGT-M) for prevention and control of genetic cancers.

METHODS

Inclusion of families with a specific pathogenic mutation or a clear family history of genetic cancers. Identification of the distribution of hereditary cancer-related mutations in families through genetic testing. After a series of assisted reproductive measures such as down-regulation, stimulation, egg retrieval, and in vitro fertilization, a biopsy of trophectoderm cells from a blastocyst was performed for single-cell level whole-genome amplification (WGA). Then, the detection of chromosomal aneuploidies was performed by karyomapping. Construction of a haplotype-based linkage analysis to determine whether the embryo carries the mutation. Meanwhile, we performed CNV testing. Finally, embryos can be selected for transfer, and the results will be verified in 18-22 weeks after pregnancy.

RESULTS

Six couples with a total of 7 cycles were included in our study. Except for cycle 1 of case 5 which did not result in a transferable embryo, the remaining 6 cycles produced transferable embryos and had a successful pregnancy. Four couples have had amniotic fluid tests to confirm that the fetus does not carry the mutation, while 1 couple was not tested due to insufficient pregnancy weeks. And the remaining couples had to induce labor due to fetal megacystis during pregnancy.

CONCLUSION

Our strategy has been proven to be feasible. It can effectively prevent transmission of hereditary cancer-related mutations to offspring during the prenatal stage.

Early-Onset Colorectal Cancer: Prevalence, Risk Factors, and Clinical Features Among Commercially Insured Adults in the United States

BACKGROUND

 The incidence of colorectal cancer (CRC) in patients younger than 50 has been rising over the last several decades, accounting for up to 25% of total cases. Despite the screening age recently being lowered to 45, a significant proportion of cases would still arise at younger ages prior to screening. Nonfamilial early-onset CRC remains a particular concern. Identification of risk factors and clinical features in this age group is needed to improve detection.

METHODS

In this retrospective cohort analysis using claims data from the Truven Health MarketScan® Commercial Claims insurance database from 2007 to 2017, patients were identified with colon and rectal cancer, compared across three age groups (ages 18-40, 40-50, and >50), and analyzed for risk factors and clinical features.

RESULTS

Female sex was more prevalent in the younger age group compared to age >50 (54% and 51.9% vs. 49.6%), with little change noted between rectal cancer age groups by sex. A higher percentage of younger patients were in the obese age groups compared with older groups for colon cancer, particularly the morbidly obese with BMI >40 (24.94%, 25.75%, and 21.34% in the three age groups). Abdominal pain was a common presenting symptom identified in the age groups <50 compared with age >50 (25% and 19% vs. 14%), along with hematochezia, weight loss, and anemia.

CONCLUSIONS

Morbid obesity and female sex may be important risk factors among patients with early-onset CRC. The presence of abdominal pain was more common among the early-onset CRC cohort.

A Different Way to Think About Syndromes of Hereditary Colorectal Cancer

BACKGROUND

Hereditary colorectal cancer is an increasingly complex field in which the commoner syndromes are being augmented by rarer genetic presentations contributing to familial polyposis and colorectal cancer. Coming to grips with the complexity is difficult because of the phenotypic and genotypic overlap between syndromes.

OBJECTIVE

This study aimed to describe a new way of thinking about syndromes of hereditary colorectal cancer based on their embryonic tissue of origin.

DATA SOURCES

Articles were searched through PubMed and MEDLINE.

STUDY SELECTION

The terms "hereditary colorectal cancer," "syndromes of hereditary colorectal cancer," and "hereditary polyposis" were used to direct the search.

RESULTS

Primarily endoderm-derived syndromes were different from mesoderm-derived syndromes in their genetics, molecular biology, histology, and clinical course.

LIMITATIONS

There is considerable phenotypic and genotypic overlap between syndromes, even when considering embryonic tissue of origin.

CONCLUSIONS

Thinking about hereditary syndromes of colorectal cancer from the perspective of embryonic tissue of origin provides a fresh look at phenotype and genotype that opens new areas of exploration.

UNA FORMA DIFERENTE DE PENSAR SOBRE LOS SNDROMES DEL CNCER COLORRECTAL HEREDITARIO

ANTECEDENTES:El cáncer colorrectal hereditario es un campo cada vez más complejo donde los síndromes más comunes se ven aumentados por presentaciones genéticas más raras que contribuyen a la poliposis familiar y al cáncer colorrectal. Hacer frente a esta complejidad resulta difícil debido a la superposición fenotípica y genotípica entre los síndromes.OBJETIVO:En este artículo, describimos una nueva forma de pensar sobre los síndromes de cáncer colorrectal hereditario en función del origen de su tejido embrionario.FUENTES DE DATOS:Se realizaron búsquedas de artículos en Pubmed y Medline.SELECCIÓN DE ESTUDIOS:Se utilizaron los términos "cáncer colorrectal hereditario", "síndromes de cáncer colorrectal hereditario", "poliposis hereditaria" para dirigir la búsqueda.RESULTADOS:Principalmente los síndromes derivados del endodermo fueron diferentes a los síndromes derivados del mesodermo en su genética, biología molecular, histología y curso clínico.LIMITACIONES:Existe una superposición fenotípica y genotípica considerable entre los síndromes, incluso cuando se considera el tejido de origen embrionario.CONCLUSIÓN:Pensar en los síndromes hereditarios del cáncer colorrectal desde la perspectiva del tejido embrionario de origen proporciona una nueva mirada al fenotipo y al genotipo que abre nuevas áreas de exploración. (Traducción-Dr Osvaldo Gauto ).

A Journey from Blood Cells to Genes and Back

I was attracted to hematology because by combining clinical findings with the use of a microscope and simple laboratory tests, one could often make a diagnosis. I was attracted to genetics when I learned about inherited blood disorders, at a time when we had only hints that somatic mutations were also important. It seemed clear that if we understood not only what genetic changes caused what diseases but also the mechanisms through which those genetic changes contribute to cause disease, we could improve management. Thus, I investigated many aspects of the glucose-6-phosphate dehydrogenase system, including cloning of the gene, and in the study of paroxysmal nocturnal hemoglobinuria (PNH), I found that it is a clonal disorder; subsequently, we were able to explain how a nonmalignant clone can expand, and I was involved in the first trial of PNH treatment by complement inhibition. I was fortunate to do clinical and research hematology in five countries; in all of them, I learned from mentors, from colleagues, and from patients.

Anticarcinogenic effect of gold nanoparticles synthesized from Albizia lebbeck on HCT-116 colon cancer cell lines

Colon cancer is one of the major prevailing types of cancer worldwide. It has been the most important public health difficulty. Thus, we planned phytoconstituents arbitrated synthesis of gold nanoparticles (AuNPs) and examined their curative efficacy against the colon cancer (HCT-116) cells. In this current study, we formulated the AuNPs by using Albizia lebbeck (AL) aqueous leaf extract by the green method and synthesized AL-AuNPs were distinguished by UV-visible spectroscopy (UV-vis), energy dispersive X-ray diffraction (XRD), selected area (electron) diffraction (SAED) pattern, Fourier transform infrared spectroscopy (FTIR) and high-resolution transmission electron microscopy (HR-TEM). Synthesized AL-AuNPs confirmed by the UV absorption highest at 535 nm and the crystal structure of AL-AuNPs was additionally established by XRD and SAED pattern. HR-TEM images explained the size and morphology allocation of nanoparticles. FTIR analysis confirmed the presence of alkynes, aromatic compounds, and alkenes of biomolecules in AL-AuNPs. Furthermore, AL-AuNPs induced cytotoxicity at the IC₅₀ concentration 48 µg/ml and also induced apoptosis by enhanced ROS production, decreased ΔΨm, apoptotic morphological changes by AO/EtBr and altering pro and anti-apoptotic protein expressions were analyzed in HCT-116 colon cancer cells. The findings of this investigation proved that the AL-AuNPs were revealed the potential anticancer activity against colon cancer (HCT-116) cells.

Febuxostat reduces muscle wasting in tumor-bearing mice with LM8 osteosarcoma cells via inhibition of reactive oxygen species generation

Cachexic condition due to malignant tumors has been a challenging problem. The aim of this study is to analyze effects of febuxostat on both in vitro and in vivo models of the wasting of skeletal muscles, due to LM8 osteosarcoma cells. C2C12 myotubes were incubated in the conditioned medium of LM8. Febuxostat was added at a concentration of 3 µM and 30 µM, and ROS, diameter of myotubes, and expression of atrogin-1 were analyzed. Furthermore, an in vivo study was performed by subcutaneous injection of LM8 on C3H mice. Febuxostat was administered in the drinking water at 5 µg/ml, and 25 µg/ml. In addition, tumor-bearing mice without febuxostat (group TB) and control mice (group C) were established. At 4 weeks, body weight, wet weights of the gastrocnemius muscles, XO activity, 8-OHdG, and expression of TNF-α and IL-6 were evaluated. ROS generation, atrophy of myotubes, and upregulation of atrogin-1 were clearly observed in C2C12 myotubes following incubation in the conditioned medium. These pathological conditions were significantly inhibited by febuxostat administration. Furthermore, mice in group TB showed significant loss of body weight and muscle weight in which XO activity, 8-OHdG, and expression of IL-6 were significantly increased compared to those in group C. Febuxostat administration not only significantly improved the body weight and muscleweight, but also reduced markers of oxidative stress and pro-inflammatory cytokines. Febuxostat did not show anti-tumor effects. Febuxostat, which is clinically used for treatment of hyperuricemia, is effective against the wasting of the skeletal muscles induced by LM8 osteosarcoma cells.

The ER-mitochondria Ca2+ signaling in cancer progression: Fueling the monster

Cancer is a leading cause of death worldwide. All major tumor suppressors and oncogenes are now recognized to have fundamental connections with metabolic pathways. A hallmark feature of cancer cells is a reprogramming of their metabolism even when nutrients are available. Increasing evidence indicates that most cancer cells rely on mitochondrial metabolism to sustain their energetic and biosynthetic demands. Mitochondria are functionally and physically coupled to the endoplasmic reticulum (ER), the major calcium (Ca²⁺) storage organelle in mammalian cells, through special domains known as mitochondria-ER contact sites (MERCS). In this domain, the release of Ca²⁺ from the ER is mainly regulated by inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), a family of Ca²⁺ release channels activated by the ligand IP3. IP3R mediated Ca²⁺ release is transferred to mitochondria through the mitochondrial Ca²⁺ uniporter (MCU). Once in the mitochondrial matrix, Ca²⁺ activates several proteins that stimulate mitochondrial performance. The role of IP3R and MCU in cancer, as well as the other proteins that enable the Ca²⁺ communication between these two organelles is just beginning to be understood. Here, we describe the function of the main players of the ER mitochondrial Ca²⁺ communication and discuss how this particular signal may contribute to the rise and development of cancer traits.

The shift of the paradigm between ageing and diseases

In the area of the Medical Sciences, the chronological age has always been, and still is, an indicator by which we try to understand the health status of an individual. However, besides considering people born with an already expressed disease, each human genome has sequence alterations called predisposing mutations; carriers of such genetic alterations have an increased risk of contracting diseases during their life. In addition, the exposome, i.e. the totality of environmental noxae (“hits”) to which our body is exposed throughout life (through ingestion, breathing, body surface hits, and psychosociological stress agents, etc.) contributes to increase gradually but inexorably the frailty of an organism, and this process is usually referred to as “physiological ageing”. This position paper proposes that we invert our visual angle and view the passage-of-time not as the cause of diseases, but consider the genome alterations present at birth and the noxae received during our life as the real major causes of ageing. The Biomedical Sciences are now increasingly unraveling the etiopathogenesis of most chronic degenerative diseases; thus, it will be possible to monitor and treat those that most contribute to the increased frailty of each person, which is now referred to with the misnomer “physiological ageing”. These concepts are not banal; indeed, they imply that we must try to avoid the causes of alterations that result later in chronic degenerative diseases. Thus, we should shift our attention from the cure to the prevention of alterations/diseases also to improve both the length and quality of our life. Moreover, this approach involves real personalized or individualized medicine, thus conferring a more direct benefit to each of us by finalizing either the cure or the monitoring of diseases.

Stem cell replication, somatic mutations and role of randomness in the development of cancer

An intense scientific debate has recently taken place relating to the "bad luck" hypothesis in cancer development, namely that intrinsic random, and therefore unavoidable, mutagenic events would have a predominant role in tumorigenesis. In this article we review the main contributions to this debate and explain the reasons why the claim that cancer is mostly explained by intrinsic random factors is unsupported by data and theoretical models. In support of this, we present an analysis showing that smoking-induced mutations are more predictive of cancer risk than the lifetime number of stem cell cellular divisions.

Early-onset colorectal cancer in young individuals

Treatment of young adults with colorectal cancer (CRC) represents an unmet clinical need, especially as diagnosis in this population might lead to the greatest loss of years of life. Since 1994, CRC incidence in individuals younger than 50 years has been increasing by 2% per year. The surge in CRC incidence in young adults is particularly alarming as the overall CRC frequency has been decreasing. Early-onset CRC are characterized by a more advanced stage at diagnosis, poorer cell differentiation, higher prevalence of signet ring cell histology, and left colon-sided location of the primary tumor. Among EO-CRC, approximately 30% of patients are affected by tumors harboring mutations causing hereditary cancer predisposing syndromes, and 20% have familial CRC. Most notably, the remaining 50% of EO-CRC patients have neither hereditary syndromes nor familial CRC, thus representing a formidable challenge for research. In this review article we summarize epidemiology, clinical and molecular features, heredity and outcome of treatments of EO-CRC, and provide considerations for future perspectives.

A stochastic model of myeloid cell lineages in hematopoiesis and pathway mutations in acute myeloid leukemia

A model for hematopoiesis is presented that explicitly includes the erythrocyte, granulocyte, and thrombocyte lineages and their common precursors. A small number of stem cells proliferate and differentiate through different compartments to produce the vast number of blood cells needed every day. Growth factors regulate the proliferation of cells dependent on the current demand. We provide a steady state analysis of the model and rough parameter estimates. Furthermore, we extend the model to include mutations that alter the replicative capacity of cells and introduce differentiation blocks. With these mutations the model develops signs of acute myeloid leukemia.

Higher frequency but random distribution of EGFR mutation subtypes in familial lung cancer patients

Despite the advancement of epidermal growth factor receptor (EGFR) inhibitors in lung cancer therapy, it remains unclear whether EGFR mutation status in familial lung cancers is different from that of sporadic cases. In this multicenter retrospective study, we compared both the EGFR mutation frequency and patterns between familial and sporadic cases. The results explored that family history of lung cancer is an independent predictor for higher EGFR mutation rate in 1713 lung adenocarcinoma patients (Odd ratio 1.68, 95% CI 1.06–2.67, P = 0.028). However, the distribution of EGFR mutation subtypes was similar to that of sporadic cases. Part of our study involved 40 lung cancer families with at least 2 tumor tissues available within each single family (n = 88) and there was no familial aggregation pattern in EGFR mutation subtypes. There were two families harboring the YAP1 R331W germline risk allele and EGFR mutation statuses among YAP1 family members also varied. These phenomena may hint at the direction of future research into lung carcinogenesis and EGFR mutagenesis.

Genetic and epigenetic alterations in normal tissues have differential impacts on cancer risk among tissues

Genetic and epigenetic alterations are both involved in carcinogenesis, and their low-level accumulation in normal tissues constitutes cancer risk. However, their relative importance has never been examined, as measurement of low-level mutations has been difficult. Here, we measured low-level accumulations of genetic and epigenetic alterations in normal tissues with low, intermediate, and high cancer risk and analyzed their relative effects on cancer risk in the esophagus and stomach. Accumulation of genetic alterations, estimated as a frequency of rare base substitution mutations, significantly increased according to cancer risk in esophageal mucosae, but not in gastric mucosae. The mutation patterns reflected the exposure to lifestyle risk factors. In contrast, the accumulation of epigenetic alterations, measured as DNA methylation levels of marker genes, significantly increased according to cancer risk in both tissues. Patients with cancer (high-risk individuals) were precisely discriminated from healthy individuals with exposure to risk factors (intermediate-risk individuals) by a combination of alterations in the esophagus (odds ratio, 18.2; 95% confidence interval, 3.69-89.9) and by only epigenetic alterations in the stomach (odds ratio, 7.67; 95% confidence interval, 2.52-23.3). The relative importance of epigenetic alterations upon genetic alterations was 1.04 in the esophagus and 2.31 in the stomach. The differential impacts among tissues will be critically important for effective cancer prevention and precision cancer risk diagnosis.

Ancient oncogenesis, infection and human evolution

The recent discovery that malignant neoplastic lesions date back nearly 2 million years ago not only highlights the antiquity of cancer in the human lineage, but also provides remarkable insight into ancestral hominin disease pathology. Using these Early Pleistocene examples as a point of departure, we emphasize the prominent role of viral and bacterial pathogens in oncogenesis and evaluate the impact of pathogens on human evolutionary processes in Africa. In the Shakespearean vernacular "what's past is prologue," we highlight the significance of novel information derived from ancient pathogenic DNA. In particular, and given the temporal depth of human occupation in sub-Saharan Africa, it is emphasized that the region is ideally positioned to play a strategic role in the discovery of ancient pathogenic drivers of not only human mortality, but also human evolution. Ancient African pathogen genome data can provide novel revelations concerning human-pathogen coevolutionary processes, and such knowledge is essential for forecasting the ways in which emerging zoonotic and increasingly transmissible diseases might influence human demography and longevity in the future.

Inequality in genetic cancer risk suggests bad genes rather than bad luck

Heritability is often estimated by decomposing the variance of a trait into genetic and other factors. Interpreting such variance decompositions, however, is not straightforward. In particular, there is an ongoing debate on the importance of genetic factors in cancer development, even though heritability estimates exist. Here we show that heritability estimates contain information on the distribution of absolute risk due to genetic differences. The approach relies on the assumptions underlying the conventional heritability of liability model. We also suggest a model unrelated to heritability estimates. By applying these strategies, we describe the distribution of absolute genetic risk for 15 common cancers. We highlight the considerable inequality in genetic risk of cancer using different metrics, e.g., the Gini Index and quantile ratios which are frequently used in economics. For all these cancers, the estimated inequality in genetic risk is larger than the inequality in income in the USA.

Health Equity and the Fallacy of Treating Causes of Population Health as if They Sum to 100

Numerous examples exist in population health of work that erroneously forces the causes of health to sum to 100%. This is surprising. Clear refutations of this error extend back 80 years. Because public health analysis, action, and allocation of resources are ill served by faulty methods, I consider why this error persists. I first review several high-profile examples, including Doll and Peto's 1981 opus on the causes of cancer and its current interpretations; a 2015 high-publicity article in Science claiming that two thirds of cancer is attributable to chance; and the influential Web site "County Health Rankings & Roadmaps: Building a Culture of Health, County by County," whose model sums causes of health to equal 100%: physical environment (10%), social and economic factors (40%), clinical care (20%), and health behaviors (30%). Critical analysis of these works and earlier historical debates reveals that underlying the error of forcing causes of health to sum to 100% is the still dominant but deeply flawed view that causation can be parsed as nature versus nurture. Better approaches exist for tallying risk and monitoring efforts to reach health equity.

Cancer Prevention and Interception: A New Era for Chemopreventive Approaches

At several recent, internationally attended scientific meetings, including the American Association for Cancer Research (AACR)'s "Shaping the Future of Cancer Prevention: A Roadmap for Integrative Cancer Science and Public Health" summit in Leesburg (VA) and the AACR Annual Meeting in New Orleans, the focus on cancer prevention to reduce cancer-related deaths was extensively discussed with renewed attention and emphasis. Cancer prevention should be actively proposed even to healthy individuals, and not just to individuals with high cancer risk. We discuss evaluation of a high cancer risk versus the relatively low risk for side effects of chemopreventive agents. The concept of cancer interception, which is halting transformed cells from becoming malignant cancers, should be adopted for cancer prevention. Potential prevention/interception actions include adopting healthy life style and avoiding carcinogens, repressing inflammation and pathologic angiogenesis, controlling metabolism, correcting insulin resistance and other metabolic alterations. Current drugs with limited toxicity can be repurposed to reduce cancer incidence. Aspirin is now being recommended for the prevention of colorectal cancer and it prevents other neoplasms as well. Metformin and β-blockers could be valuable for reducing pancreatic and breast cancer onset. On the basis of the evaluation of cancer risk, we here call for personalized approaches for cancer prevention and preventive interception and we envisage a list of measures and potential guidelines for preventive and interceptive strategies to reduce cancer burden. Investment into translational research to bring these approaches into public health policies and in the clinic is urgently needed. Clin Cancer Res; 22(17); 4322-7. ©2016 AACR.

The Interplay of Reactive Oxygen Species, Hypoxia, Inflammation, and Sirtuins in Cancer Initiation and Progression

The presence of ROS is a constant feature in living cells metabolizing O2. ROS concentration and compartmentation determine their physiological or pathological effects. ROS overproduction is a feature of cancer cells and plays several roles during the natural history of malignant tumor. ROS continuously contribute to each step of cancerogenesis, from the initiation to the malignant progression, acting directly or indirectly. In this review, we will (a) underline the role of ROS in the pathway leading a normal cell to tumor transformation and progression, (b) define the multiple roles of ROS during the natural history of a tumor, (c) conciliate many conflicting data about harmful or beneficial effects of ROS, (d) rethink the importance of oncogene and tumor suppressor gene mutations in relation to the malignant progression, and (e) collocate all the cancer hallmarks in a mechanistic sequence which could represent a "physiological" response to the initial growth of a transformed stem/pluripotent cell, defining also the role of ROS in each hallmark. We will provide a simplified sketch about the relationships between ROS and cancer. The attention will be focused on the contribution of ROS to the signaling of HIF, NFκB, and Sirtuins as a leitmotif of cancer initiation and progression.

Strategies to Prevent "Bad Luck" in Cancer

It is impossible to predict exactly who will develop a cancer and who will not. We know that several “risk factors” may increase the chance of getting cancer and that risk increases with age. However, even with that in mind we seem to be able to explain only a certain number of cancers. Recently, Tomasetti and Vogelstein published a provocative article in Science stating that a large percentage of cancers may be due to “bad luck” (stochastic mutation events during DNA replication) and only a few to carcinogens, pathogens, or inherited genes and that this should impact public health policies. However, their intriguing analysis has numerous limitations, some of which have already been commented upon, including the likely biased subset of cancers and that finding a correlation does not signify a cause-effect mechanism. Here, we point out that there may also be an alternative explanation for the data, the cancer stem cell hypothesis, which postulates that cancers are derived from tissue stem cells and not from somatic differentiated cells. We also highlight the importance of the tissue microenvironment in the growth of transformed cells and outline a table of concurrent factors for several cancers. The message communicated to the public should not be one of helplessness in avoiding cancers, particularly given the now extensive knowledge of known risk factors and several agents/behaviors that can lower risk for specific cancers. While some tumors will still be due to chance, prevention should still be a primary goal for public health policies.