The natural history of cancer

Nonlinear progression during the occult transition establishes cancer lethality

Cancer screening relies upon a linear model of neoplastic growth and progression. Yet, historical observations suggest that malignant progression is uncoupled from growth, which may explain the paradoxical increase in early-stage breast cancer detection without a dramatic reduction in metastasis. Here, we lineage trace millions of transformed cells and thousands of tumors using a cancer rainbow mouse model of HER2 (also known as ERBB2)-positive breast cancer. Transition rates from field cell to screen-detectable tumor to symptomatic tumor were estimated from a dynamical model of tumor development. Field cells were orders of magnitude less likely to transition to a screen-detectable tumor than the subsequent transition from screen-detectable tumor to symptomatic tumor. Our model supports a critical 'occult' transition in tumor development during which a transformed cell becomes a bona fide neoplasm. Lineage tracing and test by transplantation revealed that nonlinear progression during the occult transition gives rise to nascent lethal cancers at screen detection. Simulations illustrated how occult transition rates are a critical determinant of tumor growth and malignancy. Our data provide direct experimental evidence that cancers can deviate from the predictable linear progression model that is foundational to current screening paradigms.

Current treatments for oropharyngeal squamous cell carcinoma and the move towards molecular therapy

OBJECTIVES

In this review, we discuss oropharyngeal squamous cell carcinoma (OPSCC) treatment options with a focus on the molecular mechanisms of OPSCC in head and neck squamous cell carcinoma (HNSCC) and head and neck cancers (HNCs). Treatment can be radical intent (aim for cure) or palliative intent (aim for disease control and symptom management). OPSCC is a prominent subset of HNSCCs in Australia and the Western World.

METHOD

We looked at the current conventional treatment options with an overview of recent advances and future endeavours.

KEY FINDINGS

We identified that radiotherapy is the primary management for OPSCC in most countries, including the USA, UK, NZ, and Australia. In contrast, surgery is only considered for superficial OPSCC or neck surgery. If surgery is incomplete, then definitive management still requires radiotherapy.

CONCLUSION

Molecular therapy is largely at the preclinical stage, with cetuximab, nivolumab, pembrolizumab, Lenvatinib, and bevacizumab being tested clinically currently.

Red Blood Cell Transfusions in Patients with Advanced Cancer Receiving Home Palliative Care

Background: Red blood cell (RBC) transfusion is the standard treatment for anemia in advanced cancer. Nevertheless, guidelines for managing this condition are still not exhaustive. Objective: To investigate frequency, timing, and clinical characteristics associated with RBC transfusions in patients with advanced cancer assisted by at-home oncological care service and to evaluate the association between parameters at the entry and the possibility of receiving RBC transfusions during homecare. Design: Retrospective observational study without medication. Setting/Subjects: Patients with advanced cancer entered in homecare during 2021 living in Bologna (Italy). Measurements: Gender, tumor primary site, oncological therapy, and symptoms at the entry were considered as possible factors in a binary logistic regression for the possibility of receiving at least one RBC transfusion during assistance. Data about transfusions were analyzed, and the transfusion history for each patient from the entry to death was traced. Results: Among the 1108 patients admitted, 179 (16.2%) were given at least one RBC transfusion during homecare. Genitourinary, hematological malignancies, and being still in therapy for advanced cancer are associated with a higher probability of receiving RBC transfusion during assistance (p = 0.017, p < 0.001, and p = 0.032, respectively). Half of the patients (52%) underwent RBC transfusions less than a month before death. Duration of the assistance was correlated with the period from last transfusion to death (p < 0.001). Conclusion: Hematological and genitourinary cancer and being in simultaneous care at the entry were associated with transfusion. Although the appropriateness of this treatment remains to be defined in this population, transfused patients frequently received "late in life" transfusions.

Onco-Circuit Addiction and Onco-Nutrient mTORC1 Signaling Vulnerability in a Model of Aggressive T Cell Malignancy

How genetic lesions drive cell transformation and whether they can be circumvented without compromising function of non-transformed cells are enduring questions in oncology. Here we show that in mature T cells-in which physiologic clonal proliferation is a cardinal feature- constitutive MYC transcription and Tsc1 loss in mice modeled aggressive human malignancy by reinforcing each other's oncogenic programs. This cooperation was supported by MYC-induced large neutral amino acid transporter chaperone SLC3A2 and dietary leucine, which in synergy with Tsc1 deletion overstimulated mTORC1 to promote mitochondrial fitness and MYC protein overexpression in a positive feedback circuit. A low leucine diet was therapeutic even in late-stage disease but did not hinder T cell immunity to infectious challenge, nor impede T cell transformation driven by constitutive nutrient mTORC1 signaling via Depdc5 loss. Thus, mTORC1 signaling hypersensitivity to leucine as an onco-nutrient enables an onco-circuit, decoupling pathologic from physiologic utilization of nutrient acquisition pathways.

From complexity to clarity: unravelling tumor heterogeneity through the lens of tumor microenvironment for innovative cancer therapy

Despite the tremendous clinical successes recorded in the landscape of cancer therapy, tumor heterogeneity remains a formidable challenge to successful cancer treatment. In recent years, the emergence of high-throughput technologies has advanced our understanding of the variables influencing tumor heterogeneity beyond intrinsic tumor characteristics. Emerging knowledge shows that drivers of tumor heterogeneity are not only intrinsic to cancer cells but can also emanate from their microenvironment, which significantly favors tumor progression and impairs therapeutic response. Although much has been explored to understand the fundamentals of the influence of innate tumor factors on cancer diversity, the roles of the tumor microenvironment (TME) are often undervalued. It is therefore imperative that a clear understanding of the interactions between the TME and other tumor intrinsic factors underlying the plastic molecular behaviors of cancers be identified to develop patient-specific treatment strategies. This review highlights the roles of the TME as an emerging factor in tumor heterogeneity. More particularly, we discuss the role of the TME in the context of tumor heterogeneity and explore the cutting-edge diagnostic and therapeutic approaches that could be used to resolve this recurring clinical conundrum. We conclude by speculating on exciting research questions that can advance our understanding of tumor heterogeneity with the goal of developing customized therapeutic solutions.

On a sugar high: Role of O-GlcNAcylation in cancer

Recent advances in the understanding of the molecular mechanisms underlying cancer progression have led to the development of novel therapeutic targeting strategies. Aberrant glycosylation patterns and their implication in cancer have gained increasing attention as potential targets due to the critical role of glycosylation in regulating tumor-specific pathways that contribute to cancer cell survival, proliferation, and progression. A special type of glycosylation that has been gaining momentum in cancer research is the modification of nuclear, cytoplasmic, and mitochondrial proteins, termed O-GlcNAcylation. This protein modification is catalyzed by an enzyme called O-GlcNAc transferase (OGT), which uses the final product of the Hexosamine Biosynthetic Pathway (HBP) to connect altered nutrient availability to changes in cellular signaling that contribute to multiple aspects of tumor progression. Both O-GlcNAc and its enzyme OGT are highly elevated in cancer and fulfill the crucial role in regulating many hallmarks of cancer. In this review, we present and discuss the latest findings elucidating the involvement of OGT and O-GlcNAc in cancer.

Cancer metastasis: Molecular mechanisms and clinical perspectives

Metastatic progression combined with non-responsiveness towards systemic therapy often shapes the course of disease for cancer patients and commonly determines its lethal outcome. The complex molecular events that promote metastasis are a combination of both, the acquired pro-metastatic properties of cancer cells and a metastasis-permissive or -supportive tumor micro-environment (TME). Yet, dissemination is a challenging process for cancer cells that requires a series of events to enable cancer cell survival and growth. Metastatic cancer cells have to initially detach themselves from primary tumors, overcome the challenges of their intravasal journey and colonize distant sites that are suited for their metastases. The implicated obstacles including anoikis and immune surveillance, can be overcome by intricate intra- and extracellular signaling pathways, which we will summarize and discuss in this review. Further, emerging modulators of metastasis, like the immune-microenvironment, microbiome, sublethal cell death engagement, or the nervous system will be integrated into the existing working model of metastasis.

Hematopoietic and Chronic Myeloid Leukemia Stem Cells: Multi-Stability versus Lineage Restriction

There is compelling evidence to support the view that the cell-of-origin for chronic myeloid leukemia is a hematopoietic stem cell. Unlike normal hematopoietic stem cells, the progeny of the leukemia stem cells are predominantly neutrophils during the disease chronic phase and there is a mild anemia. The hallmark oncogene for chronic myeloid leukemia is the BCR-ABLp210 fusion gene. Various studies have excluded a role for BCR-ABLp210 expression in maintaining the population of leukemia stem cells. Studies of BCR-ABLp210 expression in embryonal stem cells that were differentiated into hematopoietic stem cells and of the expression in transgenic mice have revealed that BCR-ABLp210 is able to veer hematopoietic stem and progenitor cells towards a myeloid fate. For the transgenic mice, global changes to the epigenetic landscape were observed. In chronic myeloid leukemia, the ability of the leukemia stem cells to choose from the many fates that are available to normal hematopoietic stem cells appears to be deregulated by BCR-ABLp210 and changes to the epigenome are also important. Even so, we still do not have a precise picture as to why neutrophils are abundantly produced in chronic myeloid leukemia.

Impact of cancer evolution on immune surveillance and checkpoint inhibitor response

Intratumour heterogeneity (ITH) is pervasive across all cancers studied and may provide the evolving tumour multiple routes to escape immune surveillance. Immune checkpoint inhibitors (CPIs) are rapidly becoming standard of care for many cancers. Here, we discuss recent work investigating the influence of ITH on patient response to immune checkpoint inhibitor (CPI) therapy. At its simplest, ITH may confound the diagnostic accuracy of predictive biomarkers used to stratify patients for CPI therapy. Furthermore, ITH is fuelled by mechanisms of genetic instability that can both engage immune surveillance and drive immune evasion. A greater appreciation of the interplay between ITH and the immune system may hold the key to increasing the proportion of patients experiencing durable responses from CPI therapy.

Attack of the Subclones: Accurate Detection of Mutational Heterogeneity in Bulk DNA from Tumors

Tumors are often polyclonal and are therefore heterogenous in their genomic and molecular profiles, which contributes to drug resistance and treatment failure. The methods used to detect these heterogenous differences in tumor samples are critical, but findings have been hindered by methodological inability to detect low-frequency subclones in bulk DNA. Chang et al. (2020) have addressed some of these methodological issues.

Can conventional DWI accurately assess the size of endometrial cancer?

PURPOSE

To compare T2-weighted image (T2WI) and conventional Diffusion-weighted image (cDWI) of magnetic resonance imaging (MRI) for sensitivity of qualitative diagnosis and accuracy of tumor size (TS) measurement in endometrial cancer (EC). Meanwhile, the effect of the lesion size itself and tumor grade on the ability of T2WI and cDWI of TS assessment was explored. Ultimately, the reason of deviation on size evaluation was studied.

MATERIALS AND METHODS

34 patients with EC were enrolled. They were all treated with radical hysterectomy and performed MR examinations before operation. Firstly, the sensitivity of T2WI alone and T2WI-DWI in qualitative diagnosis of EC were compared according to pathology. Secondly, TS on T2WI and cDWI described with longitudinal (LD) and horizontal diameter (HD) were compared to macroscopic surgical specimen (MSS) quantitatively in the entire lesions and the subgroup lesions which grouped by postoperative tumor size itself and tumor grade. Thirdly, the discrepancy of mean ADC values (ADC mean) and range ADC values (ADC range) between different zones of EC were explored.

RESULTS

For qualitative diagnosis, the sensitivity of T2WI-DWI (97%) was higher than T2WI alone (85%) (p = 0.046).For TS estimation, no significant difference (PLD = 0.579; PHD = 0.261) was observed between T2WI (LDT2WI = 3.90 cm; HDT2WI = 2.88 cm) and MSS (LD = 4.00 cm; HD = 3.06 cm), whereas TS of cDWI (LDDWI = 3.01 cm; HDDWI = 2.54 cm) were smaller than MSS (PLD = 0.002; PHD = 0.002) in all lesions. In subgroup of tumor with G1 (grade 1) and small lesion (defined as maximum diameter < 3 cm), both T2WI and cDWI were not significantly different from MSS; In subgroup of tumor with G2 + 3 (grade 2 and grade 3) and big lesion (maximum diameter ≥ 3 cm), T2WI matched well with MSS still, but DWI lost accuracy significantly. The result of ADC values between different zones of tumor showed ADC mean of EC rose from central zone to peripheral zone of tumor gradually and ADC range widened gradually.

CONCLUSION

cDWI can detect EC very sensitively. The TS on cDWI was smaller than the fact for the ECs with G2/3 and big size. The TS of T2WI was in accordance with the actual size for all ECs. The heterogeneity may be responsible for the inaccuracy of cDWI.

The Many Facets of Tumor Heterogeneity: Is Metabolism Lagging Behind?

Tumor functional heterogeneity has been recognized for decades, and technological advancements are fueling renewed interest in uncovering the cell-intrinsic and extrinsic factors that influence tumor development and therapeutic response. Intratumoral heterogeneity is now arguably one of the most-studied topics in tumor biology, leading to the discovery of new paradigms and reinterpretation of old ones, as we aim to understand the profound implications that genomic, epigenomic, and functional heterogeneity hold with regard to clinical outcomes. In spite of our improved understanding of the biological complexity of cancer, characterization of tumor metabolic heterogeneity has lagged behind, lost in a century-old controversy debating whether glycolysis or mitochondrial respiration is more influential. But is tumor metabolism really so simple? Here, we review historical and current views of intratumoral heterogeneity, with an emphasis on summarizing the emerging data that begin to illuminate just how vast the spectrum of metabolic strategies a tumor can employ may be, and what this means for how we might interpret other tumor characteristics, such as mutational landscape, contribution of microenvironmental influences, and treatment resistance.

The emerging links between chromosomal instability (CIN), metastasis, inflammation and tumour immunity

Many cancers possess an incorrect number of chromosomes, a state described as aneuploidy. Aneuploidy is often caused by Chromosomal Instability (CIN), a process of continuous chromosome mis-segregation. CIN is believed to endow tumours with enhanced evolutionary capabilities due to increased intratumour heterogeneity, and facilitating adaptive resistance to therapies. Recently, however, additional consequences and associations with CIN have been revealed, prompting the need to understand this universal hallmark of cancer in a multifaceted context. This review is focused on the investigation of possible links between CIN, metastasis and the host immune system in cancer development and treatment. We specifically focus on these links since most cancer deaths are due to the consequences of metastasis, and immunotherapy is a rapidly expanding novel avenue of cancer therapy.

Curcumin and its Potential for Systemic Targeting of Inflamm-Aging and Metabolic Reprogramming in Cancer

Pleiotropic effects of curcumin have been the subject of intensive research. The interest in this molecule for preventive medicine may further increase because of its potential to modulate inflamm-aging. Although direct data related to its effect on inflamm-aging does not exist, there is a strong possibility that its well-known anti-inflammatory properties may be relevant to this phenomenon. Curcumin's binding to various proteins, which was shown to be dependent on cellular oxidative status, is yet another feature for exploration in depth. Finally, the binding of curcumin to various metabolic enzymes is crucial to curcumin's interference with powerful metabolic machinery, and can also be crucial for metabolic reprogramming of cancer cells. This review offers a synthesis and functional links that may better explain older data, some observational, in light of the most recent findings on curcumin. Our focus is on its modes of action that have the potential to alleviate specific morbidities of the 21st century.

The Roles of DNA Methylation in the Stages of Cancer

Next year will mark 60 years since Dr. Leslie Foulds outlined his hypothesis that cancer is "a dynamic process advancing through stages that are qualitatively different," leading the way to our view of cancer progression as we know it today. Our understanding of the mechanisms of these stages has been continuously evolving this past half-century, and there has always been an active discussion of the roles of both genetic and epigenetic changes in directing this progression. In this review, we focus on the roles one particular epigenetic mark-DNA methylation-plays in these various "discontinuous" stages of cancer. Understanding these steps not only gives us a better picture of how this fascinating biological process operates, but also opens the doors to new prognostic biomarkers and therapies against these malignancies.

The molecular characteristics of colorectal cancer: Implications for diagnosis and therapy

Colorectal cancer (CRC) results from the progressive accumulation of multiple genetic and epigenetic aberrations within cells. The progression from colorectal adenoma to carcinoma is caused by three major pathways: Microsatellite instability, chromosomal instability and CpG island methylator phenotype. A growing body of scientific evidences suggests that CRC is a heterogeneous disease, and genetic characteristics of the tumors determine their prognostic outcome and response to targeted therapies. Early diagnosis and effective targeted therapies based on a current knowledge of the molecular characteristics of CRC are essential to the successful treatment of CRC. Therefore, the present review summarized the current understanding of the molecular characteristics of CRC, and discussed its implications for diagnosis and targeted therapy.

Defining key concepts of intestinal and epithelial cancer biology through the use of mouse models

Over the past 20 years, huge advances have been made in modelling human diseases such as cancer using genetically modified mice. Accurate in vivo models are essential to examine the complex interaction between cancer cells, surrounding stromal cells, tumour-associated inflammatory cells, fibroblast and blood vessels, and to recapitulate all the steps involved in metastasis. Elucidating these interactions in vitro has inherent limitations, and thus animal models are a powerful tool to enable researchers to gain insight into the complex interactions between signalling pathways and different cells types. This review will focus on how advances in in vivo models have shed light on many aspects of cancer biology including the identification of oncogenes, tumour suppressors and stem cells, epigenetics, cell death and context dependent cell signalling.

The role of tumour heterogeneity and clonal cooperativity in metastasis, immune evasion and clinical outcome

BACKGROUND

The advent of rapid and inexpensive sequencing technology allows scientists to decipher heterogeneity within primary tumours, between primary and metastatic sites, and between metastases. Charting the evolutionary history of individual tumours has revealed drivers of tumour heterogeneity and highlighted its impact on therapeutic outcomes.

DISCUSSION

Scientists are using improved sequencing technologies to characterise and address the challenge of tumour heterogeneity, which is a major cause of resistance to therapy and relapse. Heterogeneity may fuel metastasis through the selection of rare, aggressive, somatically altered cells. However, extreme levels of chromosomal instability, which contribute to intratumour heterogeneity, are associated with improved patient outcomes, suggesting a delicate balance between high and low levels of genome instability.

CONCLUSIONS

We review evidence that intratumour heterogeneity influences tumour evolution, including metastasis, drug resistance, and the immune response. We discuss the prevalence of tumour heterogeneity, and how it can be initiated and sustained by external and internal forces. Understanding tumour evolution and metastasis could yield novel therapies that leverage the immune system to control emerging tumour neo-antigens.

Blood vessel tortuosity selects against evolution of aggressive tumor cells in confined tissue environments: A modeling approach

Cancer is a disease of cellular regulation, often initiated by genetic mutation within cells, and leading to a heterogeneous cell population within tissues. In the competition for nutrients and growth space within the tumors the phenotype of each cell determines its success. Selection in this process is imposed by both the microenvironment (neighboring cells, extracellular matrix, and diffusing substances), and the whole of the organism through for example the blood supply. In this view, the development of tumor cells is in close interaction with their increasingly changing environment: the more cells can change, the more their environment will change. Furthermore, instabilities are also introduced on the organism level: blood supply can be blocked by increased tissue pressure or the tortuosity of the tumor-neovascular vessels. This coupling between cell, microenvironment, and organism results in behavior that is hard to predict. Here we introduce a cell-based computational model to study the effect of blood flow obstruction on the micro-evolution of cells within a cancerous tissue. We demonstrate that stages of tumor development emerge naturally, without the need for sequential mutation of specific genes. Secondly, we show that instabilities in blood supply can impact the overall development of tumors and lead to the extinction of the dominant aggressive phenotype, showing a clear distinction between the fitness at the cell level and survival of the population. This provides new insights into potential side effects of recent tumor vasculature normalization approaches.

The Origin and Significance of Hyperplastic Hepatocellular Islands and Nodules in Hepatic Carcinogenesis

Results of many studies, summarized in this review, support the hypothesis that carcinogen-induced hepatocellular carcinomas develop from phenotypically-altered hyperplastic hepatocellular nodules; these in turn apparently arise from smaller focal collections of hyperplastic cells referred to as hepatocellular islands. The very recent recognition that phenobarbital, when administered after carcinogens, fosters the outgrowth of hepatocellular islands and carcinomas, now provides the means for studying stages of initiation and promotion in hep-atocarcinogenesis. In addition, the recognition that enzymatic alterations, particularly the acquisition of canalicular gamma glutamyl transpeptidase activity, loss of ATP'ase activity, and loss of glucose-6-phosphatase activity that characterize many islands, have been particularly useful for measuring and evaluating the growth kinetics and heterogeneity of the islands. Evidence is presented that periportal gamma glutamyl transpeptidase positive hepatocytes are considerably more abundant after four weeks of feeding .02% 2-acetyl-aminofluorene to young rats than in control animals, and that the outgrowth of these cells is fostered by a distinctive type of periportal reparative hyperplasia. The cells appear to arise from a pool of cells that are normally abundant in periportal location in young growing rats. The studies suggest that it may now be possible to develop short term in vivo bioassays for initiators, promoters, and complete carcinogens in the rodent liver.

Evolutionary determinants of cancer

Our understanding of cancer is being transformed by exploring clonal diversity, drug resistance, and causation within an evolutionary framework. The therapeutic resilience of advanced cancer is a consequence of its character as a complex, dynamic, and adaptive ecosystem engendering robustness, underpinned by genetic diversity and epigenetic plasticity. The risk of mutation-driven escape by self-renewing cells is intrinsic to multicellularity but is countered by multiple restraints, facilitating increasing complexity and longevity of species. But our own species has disrupted this historical narrative by rapidly escalating intrinsic risk. Evolutionary principles illuminate these challenges and provide new avenues to explore for more effective control.

SIGNIFICANCE

Lifetime risk of cancer now approximates to 50% in Western societies. And, despite many advances, the outcome for patients with disseminated disease remains poor, with drug resistance the norm. An evolutionary perspective may provide a clearer understanding of how cancer clones develop robustness and why, for us as a species, risk is now off the scale. And, perhaps, of what we might best do to achieve more effective control.

Evolutionary determinants of cancer

Our understanding of cancer is being transformed by exploring clonal diversity, drug resistance, and causation within an evolutionary framework. The therapeutic resilience of advanced cancer is a consequence of its character as a complex, dynamic, and adaptive ecosystem engendering robustness, underpinned by genetic diversity and epigenetic plasticity. The risk of mutation-driven escape by self-renewing cells is intrinsic to multicellularity but is countered by multiple restraints, facilitating increasing complexity and longevity of species. But our own species has disrupted this historical narrative by rapidly escalating intrinsic risk. Evolutionary principles illuminate these challenges and provide new avenues to explore for more effective control.

SIGNIFICANCE

Lifetime risk of cancer now approximates to 50% in Western societies. And, despite many advances, the outcome for patients with disseminated disease remains poor, with drug resistance the norm. An evolutionary perspective may provide a clearer understanding of how cancer clones develop robustness and why, for us as a species, risk is now off the scale. And, perhaps, of what we might best do to achieve more effective control.

Putative mechanisms responsible for the decline in cancer prevalence during organism senescence

Most scientific literature reports that aging favors the development of cancers. Each type of cancer, however, initiates and evolves differently, and their natural history can start much earlier in life before their clinical manifestations. The incidence of cancers is spread throughout human life span, and is the result of pre- and post-natal aggressions, individual susceptibility, developmental changes that evolve continuously throughout an individual's life, and time of exposure to carcinogens. Finally, during human senescence, the incidence declines for all cancers. Frequently, the progression of cancers is also slower in aged individuals. There are several possible explanations for this decline at the tissue, cell, and molecular levels, which are described here in. It is time to ask why some tumors are characteristic of either the young, the aged, or during the time of a decline in the reproductive period, and finally, why the incidence of cancers declines late during senescence of human beings. These questions need to be addressed before the origin of cancers can be understood.

Drug Development for Metastasis Prevention

Metastatic disease is responsible for 90% of death from solid tumors. However, only a minority of metastasis-specific targets has been exploited therapeutically, and effective prevention and suppression of metastatic disease is still an elusive goal. In this review, we will first summarize the current state of knowledge about the molecular features of the disease, with particular focus on steps and targets potentially amenable to therapeutic intervention. We will then discuss the reasons underlying the paucity of metastatic drugs in the current oncological arsenal and potential ways to overcome this therapeutic gap. We reason that the discovery of novel promising targets, an increased understanding of the molecular features of the disease, the effect of disruptive technologies, and a shift in the current preclinical and clinical settings have the potential to create more successful drug development endeavors.

Biological and Clinical Implications of Clonal Heterogeneity and Clonal Evolution in Multiple Myeloma

Clonal heterogeneity and clonal evolution have emerged as critical concepts in the field of oncology over the past four decades, largely thanks to the implementation of novel technologies such as comparative genomic hybridization, whole genome/exome sequencing and epigenetic analysis. Along with the identification of cancer stem cells in the majority of neoplasia, the recognition of intertumor and intratumor variability has provided a novel perspective to understand the mechanisms behind tumor evolution and its implication in terms of treatment failure and cancer relapse or recurrence. First hypothesized over two decades ago, clonal heterogeneity and clonal evolution have been confirmed in multiple myeloma (MM), an incurable cancer of plasma cells, almost universally preceded by a pre-malignant conditioned named monoclonal gammopathy of undetermined significance (MGUS). The genetic events and molecular mechanisms underlying such evolution have been difficult to dissect. Moreover, while a role for the bone marrow microenvironment in supporting MM cell survival, proliferation and drug-resistance has been well established, whether it is directly involved in driving evolution from MGUS to MM is at present unclear. We present in this review a historical excursus on the concepts of clonal heterogeneity and clonal evolution in MM with a special emphasis on their role in the progression from MGUS to MM; the contribution of the microenvironment; and the clinical implications in terms of resistance to treatment and disease relapse/recurrence.

Diagnostic value of stool DNA testing for multiple markers of colorectal cancer and advanced adenoma: a meta-analysis

BACKGROUND AND OBJECTIVES

The diagnostic value of stool DNA (sDNA) testing for colorectal neoplasms remains controversial. To compensate for the lack of large-scale unbiased population studies, a meta-analysis was performed to evaluate the diagnostic value of sDNA testing for multiple markers of colorectal cancer (CRC) and advanced adenoma.

METHODS

The PubMed, Science Direct, Biosis Review, Cochrane Library and Embase databases were systematically searched in January 2012 without time restriction. Meta-analysis was performed using a random-effects model using sensitivity, specificity, diagnostic OR (DOR), summary ROC curves, area under the curve (AUC), and 95% CIs as effect measures. Heterogeneity was measured using the χ(2) test and Q statistic; subgroup analysis was also conducted.

RESULTS

A total of 20 studies comprising 5876 individuals were eligible. There was no heterogeneity for CRC, but adenoma and advanced adenoma harboured considerable heterogeneity influenced by risk classification and various detection markers. Stratification analysis according to risk classification showed that multiple markers had a high DOR for the high-risk subgroups of both CRC (sensitivity 0.759 [95% CI 0.711 to 0.804]; specificity 0.883 [95% CI 0.846 to 0.913]; AUC 0.906) and advanced adenoma (sensitivity 0.683 [95% CI 0.584 to 0.771]; specificity 0.918 [95% CI 0.866 to 0.954]; AUC 0.946) but not for the average-risk subgroups of either. In the methylation subgroup, sDNA testing had significantly higher DOR for CRC (sensitivity 0.753 [95% CI 0.685 to 0.812]; specificity 0.913 [95% CI 0.860 to 0.950]; AUC 0.918) and advanced adenoma (sensitivity 0.623 [95% CI 0.527 to 0.712]; specificity 0.926 [95% CI 0.882 to 0.958]; AUC 0.910) compared with the mutation subgroup. There was no significant heterogeneity among studies for subgroup analysis.

CONCLUSION

sDNA testing for multiple markers had strong diagnostic significance for CRC and advanced adenoma in high-risk subjects. Methylation makers had more diagnostic value than mutation markers.

Targeting the therapeutic effects of exercise on redox-sensitive mechanisms in the vascular endothelium during tumor progression

The American Cancer Society estimated 1.5 million new cancer cases in the United States in 2012. Although the exact number is not known, it is estimated that brain metastases occur in 20-40% of cancer patients (39). Owing to the complexity of development and the variation in tumor etiology, therapy options have been limited for a number of cancers, whereas progressive treatments have been successful for some malignancies. Combining treatment strategies has shown potential to increase positive outcomes; however, cancer remains a formidable diagnosis with no true cure. Many researchers have focused on alternative forms of cancer prevention or treatment to slow cancer progression. Studies have shown that with moderate, regular exercise signaling pathways associated with increased antioxidant activity and cellular repair are upregulated in vascular tissue; however, the physiological mechanisms are poorly understood. The purpose of this review is to examine the current literature to better understand the impact of exercise on cancer progression and tumor metastasis and discuss potential redox-related signaling in the vasculature that may be involved.

Interleukin-6--a key regulator of colorectal cancer development

Growing evidence proposes an important role for pro-inflammatory cytokines during tumor development. Several experimental and clinical studies have linked the pleiotropic cytokine interleukin-6 (IL-6) to the pathogenesis of sporadic and inflammation-associated colorectal cancer (CRC). Increased IL-6 expression has been related to advanced stage of disease and decreased survival in CRC patients. According to experimental studies, these effects are mediated through IL-6 trans-signaling promoting tumor cell proliferation and inhibiting apoptosis through gp130 activation on tumor cells with subsequent signaling through Janus kinases (JAKs) and signal transducer and activator of transcription 3 (STAT3).

During recent years, several therapeutics targeting the IL-6/STAT3 pathway have been developed and pose a promising strategy for the treatment of CRC. This review discusses the molecular mechanisms and possible therapeutic targets involved in IL-6 signaling in CRC.

The involvement of a Nanog, Klf4 and c-Myc transcriptional circuitry in the intertwining between neoplastic progression and reprogramming

One undisputed milestone of traditional oncology is neoplastic progression, which consists of a progressive selection of dedifferentiated cells driven by a chance sequence of genetic mutations. Recently it has been demonstrated that the overexpression of well-defined transcription factors reprograms somatic cells to the pluripotent stem status. The demonstration raises crucial questions as to whether and to what extent this reprogramming contributes to tumorigenesis, and whether the epigenetic changes involved in it are reversible. Here, we show for the first time that a tumor produced in vivo by a chemical carcinogen is the product of the interaction between neoplastic progression and reprogramming. The experimental model employed the prototype of ascites tumors, the Yoshida AH130 hepatoma and other neoplasias, including human melanoma. AH130 hepatoma was started in the liver by the carcinogen o-aminoazotoluene. This compound binds to and abolishes the p53 protein, producing a genomic instability that promotes both the neoplastic progression and the hepatoma reprogramming. Eventually this tumor contained 100% CD133(+) elements and pO(2)-dependent percentages of the three embryonic transcription factors Nanog, Klf4 and c-Myc. Once transferred into aerobic cultures, the minor cellular fraction expressing this triad generates various types of adherent cells, which are progressively substituted by non-tumorigenic elements committed to fibromuscular, neuronal and glial differentiation. This reprogramming appears to be accomplished stepwise, with the assembly of the triad into a sophisticated transcriptional, oxygen-dependent circuitry, in which Nanog and Klf4 antagonistically regulate c-Myc, and hence, cell hypoxia survival and cell cycle activation.

SIRT3 and cancer: tumor promoter or suppressor?

Sirtuins (SIRT1-7), the mammalian homologues of the Sir2 gene in yeast, have emerging roles in age-related diseases, such as cardiac hypertrophy, diabetes, obesity, and cancer. However, the role of several sirtuin family members, including SIRT1 and SIRT3, in cancer has been controversial. The aim of this review is to explore and discuss the seemingly dichotomous role of SIRT3 in cancer biology with particular emphasis on its potential role as a tumor promoter and tumor suppressor. This review will also discuss the potential role of SIRT3 as a novel therapeutic target to treat cancer.

Progress in understanding melanoma propagation

Melanoma, like most cancers, is a disease that wreaks havoc mostly through its propensity to spread and establish secondary tumors at sites that are anatomically distant from the primary tumor. The consideration of models of cancer progression is therefore important to understand the essence of this disease. Previous work has suggested that melanoma may propagate according to a cancer stem cell (CSC) model in which rare tumorigenic and bulk non-tumorigenic cells are organized into stable hierarchies within tumors. However, recent studies using assays that are more permissive for revealing tumorigenic potential indicate that it will not be possible to cure patients by focusing research and therapy on rare populations of cells within melanoma tumors. Studies of the nature of tumorigenic melanoma cells reveal that these cells may gain a growth, metastasis and/or therapy resistance advantage by acquiring new genetic mutations and by reversible epigenetic mechanisms. In this light, efforts to link the phenotypes, genotypes and epigenotypes of melanoma cells with differences in their in vivo malignant potential provide the greatest hope of advancing the exciting progress finally being made against this disease.

Normal stem cells and cancer stem cells: similar and different

The functional capabilities of normal stem cells and tumorigenic cancer cells are conceptually similar in that both cell types are able to proliferate extensively. Indeed, mechanisms that regulate the defining property of normal stem cells - self-renewal - also frequently mediate oncogenesis. These conceptual links are strengthened by observations in some cancers that tumorigenic cells can not only renew their malignant potential but also generate bulk populations of non-tumorigenic cells in a manner that parallels the development of differentiated progeny from normal stem cells. But cancer cells are not normal. Although tumorigenic cells and normal stem cells are similar in some ways, they are also fundamentally different in other ways. Understanding both shared and distinguishing mechanisms that regulate normal stem cell proliferation and tumor propagation is likely to reveal opportunities for improving the treatment of patients with cancer.

Precancer: sequentially acquired or predetermined?

Recognition of focal morphological intraepithelial lesions associated with the eventual development of invasive cancer has long been the sine qua non of precancer. Empirically, precancers are associated with a morphological continuum from atypia to dysplasia and invasive neoplasia. Such lesions are used as early indicators of cancers and have dramatically reduced mortality from cancers of the colon, uterine cervix, and breast. Progression has been modeled as a linear, stepwise process. Some molecular evidence supports a linear model. However, clinical studies now suggest that preexisting cofactors such as human papilloma virus (HPV) in cervical cancer determines the cell fate. Other clinical studies such as bladder, prostate, and breast suggest that many intraepithelial lesions do not progress to malignancy. The more recent experimental analyses reveal that the key molecular and genetic events even predate the emergence of visible lesions. Thus, a new nonlinear, parallel model is proposed. The parallel model suggests an origin in a putative progenitor cell that expands and invades. The clinical outcome is thus predetermined. If correct, this model suggests that "progression" to malignancy is epigenetic. Further, future assessment of biological potential will involve identification and genetic analysis of the progenitor cell populations.

Pancreatic cancer stem cells: fact or fiction?

The terms cancer-initiating or cancer stem cells have been the subject of great interest in recent years. In this review we will use pancreatic cancer as an overall theme to draw parallels with historical findings to compare to recent reports of stem-like characteristics in pancreatic cancer. We will cover such topics as label-retaining cells (side-population), ABC transporter pumps, telomerase, quiescence, cell surface stem cell markers, and epithelial-mesenchymal transitions. Finally we will integrate the available findings into a pancreatic stem cell model that also includes metastatic disease.

[Genetic abnormalities of digestive tract adenocarcinomas and correlation with the histologic sequence of their development]

Over 90% of digestive tract malignancies are adenocarcinomas (ADC) and almost 95% of them have gastric (G), colorectal (CR) or pancreatic (P) localizations. The objectives of this work are to review the genetic abnormalities of ADC in these locations and their potential coincidences, along with the histogenetic correlation of their emergence. Genetic abnormalities affecting over 50% of cases include: in G-ADC, inactivation of suppressor genes of p53, APC and DCC tumor in its intestinal variant, hypoexpression of of caderine E in the diffuse variant and hyperexpression of cyclooxygenase-2 and cyclyn D in the intestinal form; in in CR-ADC, inactivation of of genes p53, APC and DCC together with mutational activation of k-ras oncogen, and in P-ADC, the inactivation of suppressor genes p53, p16 and DPC4 along with mutational activation of k-ras oncogen. P-ADC is the one showing a more characteristic and exclusive genetic mark, followed by CR-ADC. Finally, the histogenetic correlation in the tumorigenic sequence is more evident in CR-ADC, followed by P-ADC. The complex biologic reality of G-ADC makes it more difficult to draw its genetic profile and its histogenetic correlation. In order to understand better the arguments of this work, the authors comment on the genetic-molecular basis governing the life and death of normal somatic cells and the biologic profile of the groups of genes mainly involved in tumorigenesis.

Molecular mechanisms of the effects of olive oil and other dietary lipids on cancer

Cancer is one of the main causes of mortality worldwide. Geographical differences in incidence rates suggest a key effect of environmental factors, especially diet, in its aetiology. Epidemiologic and experimental studies have found a role of dietary lipids in cancer, particularly breast, colorectal, and prostate cancers. Their incidence in the Mediterranean countries, where the main source of fat is olive oil, is lower than in other areas of the world. Human studies about the effects of dietary lipids are little conclusive, probably due to methodological issues. On the other hand, experimental data have clearly demonstrated that the influence of dietary fats on cancer depends on the quantity and the type of lipids. Whereas a high intake of n-6 PUFA and saturated fat has tumor-enhancing effects, n-3 PUFA, conjugated linoleic acid and gamma-linolenic acid have inhibitory effects. Data regarding MUFA have not always been conclusive, but high olive oil diets seem to have protective effects. Such effects can be due to oleic acid, the main MUFA in olive oil, and to certain minor compounds such as squalene and phenolic compounds. This work aims to review the current knowledge about the relationship between dietary lipids and cancer, with a special emphasis on olive oil, and the molecular mechanisms underlying these effects: modifications on the carcinogenesis stages, hormonal status, cell membrane structure and function, signal transduction pathways, gene expression, and immune system.

Darwinian medicine: a case for cancer

Epidemiological, genetic and molecular biological studies have collectively provided us with a rich source of data that underpins our current understanding of the aetiology and molecular pathogenesis of cancer. But this perspective focuses on proximate mechanisms, and does not provide an adequate explanation for the prevalence of tumours and cancer in animal species or what seems to be the striking vulnerability of Homo sapiens. The central precept of Darwinian medicine is that vulnerability to cancer, and other major diseases, arises at least in part as a consequence of the 'design' limitations, compromises and trade-offs that characterize evolutionary processes.