Risk factors and random chances

Unblinding the watchmaker: cancer treatment and drug design in the face of evolutionary pressure

INTRODUCTION

Death due to cancer is mostly associated with therapy ineffectiveness, i.e. tumor cells no longer responding to treatment. The underlying dynamics that facilitate this mutational escape from selective pressure are well studied in several other fields and several interesting approaches exist to combat this phenomenon, for example in the context of antibiotic-resistance in bacteria.

AREAS COVERED

Ninety percent of all cancer-related deaths are associated with treatment failure. Here, we discuss the common treatment modalities and prior attempts to overcome acquired resistance to therapy. The underlying molecular mechanisms are discussed and the implications of emerging resistance in other systems, such as bacteria, are discussed in the context of cancer.

EXPERT OPINION

Reevaluating emerging therapy resistance in tumors as an evolutionary mechanism to survive in a rapidly and drastically altering fitness landscape leads to novel treatment strategies and distinct requirements for new drugs. Here, we propose a scheme of considerations that need to be applied prior to the discovery of novel therapeutic drugs.

Zanthoxylum zanthoxyloides Alkaloidal Extract Improves CCl4-Induced Hepatocellular Carcinoma-Like Phenotypes in Rats

Background

Despite the enrollment of new small molecules such as Sorafenib for the treatment of hepatocellular carcinoma (HCC), HCC still remains a significant contributor to cancer-related mortality and morbidity globally. Zanthoxylum zanthoxyloides is long suspected of possessing anticancer bioactive compounds that may hold the prospect of adjunctive therapy against inflammation-related cancers such as HCC.

Objective

This study assessed the effects of an alkaloidal extract of the leaves of Zanthoxylum zanthoxyloides on CCl₄/olive oil (1 : 1 v/v)-induced HCC-like phenotypes in rats.

Materials and Methods

Zanthoxylum zanthoxyloides alkaloidal extract (ZZAE) was prepared using Soxhlet and liquid-liquid extraction methods. Subsequently, ZZAE was characterized phytochemically. In the curative method, experimental HCC was established in adult (8-10 weeks old) male Sprague-Dawley rats weighing 150-300 g by twice-daily administration of CCl₄/olive oil (1 : 1 v/v) (2 mL/kg ip). After confirmation of experimental HCC in rats, the rats were randomly reassigned into seven (7) groups of seven (7) rats each and treated daily for 12 weeks as follows: control (normal saline, 5 ml/kg po), model (CCl₄, 5 ml/kg, ip), ZZAE (50, 100, and 200 mg/kg po), carvedilol (6.25 mg/kg po), and 20% Tween20 (1 mL/rat, po). To assess whether ZZAE has a prophylactic (preventive) effect, rats were first treated with ZZAE and later exposed to CCl₄ reconstituted in olive oil.

Results

ZZAE (100 and 200 mg/kg) and carvedilol decreased tumor incidence compared to that of control. Compared to control, ZZAE (100 and 200 mg/kg) significantly (P < 0.05) improved serum GGT. Compared to control, ZZAE improved hepatohistological distortions induced by CCl₄/olive oil and also improved liver/body weight ratio. Compared to water, ZZAE arrested mitosis in the Allium cepa assay.

Conclusion

ZZAE ameliorated CCl₄/olive oil-induced HCC-like phenotype in rats and demonstrated general hepatoprotective effects by improving liver and kidney function markers. This finding rationalizes the need for further studies on ZZAE as a potential source of bioactive anti-HCC compounds.

Risk patterns of lung cancer mortality in northern Thailand

Background

Over the past decade, lung cancers have exhibited a disproportionately high mortality and increasing mortality trend in Thailand, especially in the northern region, and prevention strategies have consequently become more important in this region. Spatial analysis studies may be helpful in guiding any strategy put in place to respond to the risk of lung cancer mortality in specific areas. The aim of our study was to identify risk patterns for lung cancer mortality within the northern region of Thailand.

Methods

In the spatial analysis, the relative risk (RR) was used as a measure of the risk of lung cancer mortality in 81 districts of northern Thailand between 2008 and 2017. The RR was estimated according to the Besag-York-Mollié autoregressive spatial model performed using the OpenBUGS routine in the R statistical software package. We presented the overall and gender specific lung cancer mortality risk patterns of the region using the Quantum Geographic Information System.

Results

The overall risk of lung cancer mortality was the highest in the west of northern Thailand, especially in the Hang Dong, Doi Lo, and San Pa Tong districts. For both genders, the risk patterns of lung cancer mortality indicated a high risk in the west of northern Thailand, with females being at a higher risk than males.

Conclusions

There was distinct geographical variation in risk patterns of lung cancer mortality in Thailand. Differences could be related to differences in risk factors such as ground-based radon and air pollution. This study provides a starting point for estimating the spatial pattern of the risk of lung cancer mortality and for examining associations between geographic risk factors and lung mortality for further studies.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-6025-1) contains supplementary material, which is available to authorized users.

Epigenome-based cancer risk prediction: rationale, opportunities and challenges

The incidence of cancer is continuing to rise and risk-tailored early diagnostic and/or primary prevention strategies are urgently required. The ideal risk-predictive test should: integrate the effects of both genetic and nongenetic factors and aim to capture these effects using an approach that is both biologically stable and technically reproducible; derive a score from easily accessible biological samples that acts as a surrogate for the organ in question; and enable the effectiveness of risk-reducing measures to be monitored. Substantial evidence has accumulated suggesting that the epigenome and, in particular, DNA methylation-based tests meet all of these requirements. However, the development and implementation of DNA methylation-based risk-prediction tests poses considerable challenges. In particular, the cell type specificity of DNA methylation and the extensive cellular heterogeneity of the easily accessible surrogate cells that might contain information relevant to less accessible tissues necessitates the use of novel methods in order to account for these confounding issues. Furthermore, the engagement of the scientific community with health-care professionals, policymakers and the public is required in order to identify and address the organizational, ethical, legal, social and economic challenges associated with the routine use of epigenetic testing.

Context is everything: From cardiovascular disease to cerebral microbleeds

Increasingly, our approach to cerebrovascular disease has become blurred by evidence published in literature often without careful consideration of what this evidence implies for specific patients at hand. In this essay, we analyze key contextual issues in cerebrovascular small vessel disease, in an attempt to highlight the symbolic gap that exists between research and clinical practice, a recurring theme in medicine. We highlight the importance of considering context when using data from epidemiologic, neuroimaging, and biomarker studies in determining relevance to the patient at hand. We argue, that while biomarkers and neuroimaging may eventually serve to help to identify individuals with specific cerebrovascular diseases, we must always continue to understand patients in a specific clinical context. These reflections are particularly relevant when considering cerebral microbleeds-a key marker of cerebrovascular small vessel disease whose detection often raises thorny clinical dilemmas.

How the growth rate of host cells affects cancer risk in a deterministic way

It is well known that cancers are significantly more often encountered in some tissues than in other ones. In this paper, by using a deterministic model describing the interactions between host, effector immune and tumor cells at the tissue level, we show that this can be explained by the dependency of tumor growth on parameter values characterizing the type as well as the state of the tissue considered due to the "way of life" (environmental factors, food consumption, drinking or smoking habits, etc.). Our approach is purely deterministic and, consequently, the strong correlation (r = 0.99) between the number of detectable growing tumors and the growth rate of cells from the nesting tissue can be explained without evoking random mutation arising during DNA replications in nonmalignant cells or "bad luck". Strategies to limit the mortality induced by cancer could therefore be well based on improving the way of life, that is, by better preserving the tissue where mutant cells randomly arise.

Geographic Variations and Time Trends in Cancer Treatments in Taiwan

Background

Targeted therapies have become important treatment options for cancer care in many countries. This study aimed to examine recent trends in utilization of antineoplastic drugs, particularly the use of targeted therapies for treatment of cancer, by geographic region in Taiwan (northern, midwestern, southern, and eastern regions and the outer islands).

Methods

This was a retrospective observational study of antineoplastic agents using 2009-2012 quarterly claims data from Taiwan’s National Health Insurance Research Database. Yearly market shares by prescription volume and costs for targeted therapies among total antineoplastic agents by region were estimated. We used multivariate regression model and ANOVA to examine variations in utilization of targeted therapies between geographic regions and used ARIMA models to estimate longitudinal trends.

Results

Population-adjusted use and costs of antineoplastic drugs (including targeted therapies) were highest in the southern region of Taiwan and lowest in the outer islands. We found a 4-fold difference in use of antineoplastic drugs and a 49-fold difference in use of targeted therapies between regions if the outer islands were included. There were minimal differences in use of antineoplastic drugs between other regions with about a 2-fold difference in use of targeted therapies. Without considering the outer islands, the market share by prescription volume and costs of targeted therapies increased almost 2-fold (1.84-1.90) and 1.5-fold (1.26-1.61) respectively between 2009 and 2012. Furthermore, region was not significantly associated with use of antineoplastic agents or use of targeted therapies after adjusting for confounders. Region was associated with costs of antineoplastic agents but it was not associated with costs of targeted therapies after confounding adjustments.

Conclusions

Use of antineoplastic drugs overall and use of targeted therapies for treatment of cancer varied somewhat between regions in Taiwan; use was notably low in the outer islands. Strategies might be needed to ensure access to cancer care in each region as economic burden of cancer care increase due to growing use of targeted therapies.

"Bad Luck Mutations": DNA Mutations Are not the Whole Answer to Understanding Cancer Risk

It has been proposed that many human cancers are generated by intrinsic mechanisms that produce "Bad Luck" mutations by the proliferation of organ-specific adult stem cells. There have been serious challenges to this interpretation, including multiple extrinsic factors thought to be correlated with mutations found in cancers associated with these exposures. While support for both interpretations provides some validity, both interpretations ignore several concepts of the multistage, multimechanism process of carcinogenesis, namely, (1) mutations can be generated by both "errors of DNA repair" and "errors of DNA replication," during the "initiation" process of carcinogenesis; (2) "initiated" stem cells must be clonally amplified by nonmutagenic, intrinsic or extrinsic epigenetic mechanisms; (3) organ-specific stem cell numbers can be modified during in utero development, thereby altering the risk to cancer later in life; and (4) epigenetic tumor promoters are characterized by species, individual genetic-, gender-, developmental state-specificities, and threshold levels to be active; sustained and long-term exposures; and exposures in the absence of antioxidant "antipromoters." Because of the inevitability of some of the stem cells generating "initiating" mutations by either "errors of DNA repair" or "errors of DNA replication," a tumor is formed depending on the promotion phase of carcinogenesis. While it is possible to reduce our frequencies of mutagenic "initiated" cells, one can never reduce it to zero. Because of the extended period of the promotion phase of carcinogenesis, strategies to reduce the appearance of cancers must involve the interruption of the promotion of these initiated cells.

Changes of telomere status with aging: An update

Accumulated data have shown that most human somatic cells or tissues show irreversible telomere shortening with age, and that there are strong associations between telomere attrition and aging-related diseases, including cancers, diabetes and cognitive disorders. Although it has been largely accepted that telomere attrition is one of the major causes of aging-related disorders, critical aspects of telomere biology remain unresolved, especially the lack of standardized methodology for quantification of telomere length. Another frustrating issue is that no potentially promising methods for safe prevention of telomere erosion, or for telomere elongation, have been devised. Here, we review several methods for quantification of telomere length currently utilized worldwide, considering their advantages and drawbacks. We also summarize the results of our recent studies of human cells and tissues, mainly using quantitative fluorescence in situ hybridization and Southern blotting, including those derived from patients with progeria-prone Werner syndrome and trisomy 21, and several strains of induced pluripotent stem cells. We discuss the possible merits of using telomere shortness as an indicator, or a new marker, for diagnosis of precancerous states and aging-related disorders. In addition, we describe newly found factors that are thought to impact telomere dynamics, providing a new avenue for examining the unsolved issues related to telomere restoration and maintenance.

Clinical characteristics of synchronous colorectal cancers in Japan

BACKGROUND

Incidence and clinical characteristics of synchronous colorectal cancer (sCRC) patients significantly vary among studies, likely due to differences in surveillance methodology. If remain undetected, sCRC can progress to more advanced stages seriously aggravating patient prognosis. We studied the incidence and clinicopathological characteristics of Japanese patients with sCRCs who underwent surgery for primary CRC and received exhaustive perioperative surveillance.

METHODS

We recruited 1005 patients with surgically resected CRCs between January 2007 and December 2011. The associations of clinical and pathological factors with sCRC development were assessed by univariate and multivariate logistic regression.

RESULTS

Eighty-four patients (8.4 %) developed sCRCs, 16 of them (19.0 %) harboring three or more cancers. Companion sCRCs were smaller and earlier stage than the index lesion (P < 0.0001). In multivariate analysis, advanced age (odds ratio (OR) 1.03 per year; P = 0.009) and left colon tumor location (OR 1.78; P = 0.013) are associated with higher risk of sCRCs, particularly in females. Overall survival did not differ between solitary CRC and sCRC (P = 0.62).

CONCLUSIONS

Our results highlight the importance of perioperative colonoscopy examination to ensure the absence of sCRCs that, being small and early staged, are more difficult to detect. The incidence of sCRC, and notably of triple or more sCRCs, was higher than previously recognized. Because they are also significantly higher than expected by merely stochastic accumulation of individual cancerous lesions, we suggest that the occurrence of many sCRC reflects a hitherto uncharacterized predisposition condition.

The mathematics of cancer: integrating quantitative models

Mathematical modelling approaches have become increasingly abundant in cancer research. The complexity of cancer is well suited to quantitative approaches as it provides challenges and opportunities for new developments. In turn, mathematical modelling contributes to cancer research by helping to elucidate mechanisms and by providing quantitative predictions that can be validated. The recent expansion of quantitative models addresses many questions regarding tumour initiation, progression and metastases as well as intra-tumour heterogeneity, treatment responses and resistance. Mathematical models can complement experimental and clinical studies, but also challenge current paradigms, redefine our understanding of mechanisms driving tumorigenesis and shape future research in cancer biology.

Is bad luck the main cause of cancer?

A recent study reports that the log lifetime incidence rate across a selection of 31 cancer types is highly correlated with the log of the estimated tissue-specific lifetime number of stem cell divisions. This observation, which underscores the importance of errors in DNA replication, has been viewed as implying that most cancers arise through unavoidable bad luck, leading to the suggestion that research efforts should focus on early detection, rather than etiology or prevention. We argue that three statistical issues can, if ignored, lead analysts to incorrect conclusions. Statistics for traffic fatalities across the United States provide an example to demonstrate those inferential pitfalls. While the contribution of random cellular events to disease is often underappreciated, the role of chance is necessarily difficult to quantify. The conclusion that most cases of cancer are fundamentally unpreventable because they are the result of chance is unwarranted.