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The Vitamin D Receptor: A Tumor Suppressor in Skin


Cell Lineage Specification in Tumor Progression and Metastasis

Abstract: Cancer has long been compared to the aberrant development of human tissues. It was in the mid-19th century writings of Rudolf Virchow and Joseph Recamier that malignant tissue was first proposed to originate from embryonal cells. More contemporary perspectives on malignant progression are founded on the tenant that tumors emerge from somatic tissues. Yet examples linking the biological properties of cancer to developmental processes, both aberrant and normal, abound. In this review, we will discuss how the developmental lineage of tumor cells can influence the course of cancer metastasis. As new molecular mechanisms that control cell fate in various tissues are being rapidly uncovered, understanding how these well orchestrated programs can be subverted in human diseases should provide intriguing avenues for fundamental biological discoveries and new therapeutic opportunities in cancer. ... Read more

TNF-alpha Antagonism and Cancer Risk in Rheumatoid Arthritis: Is Continued Vigilance Warranted?

Abstract: Rheumatoid arthritis (RA) is a chronic, systemic inflammatory arthritis that can lead to significant damage and dysfunction of involved joints. Prior to 1998, treatment options were limited to disease modifying anti-rheumatic drugs, commonly referred to as DMARDs like methotrexate, sulfasalazine, hydroxychloroquine, and gold salts. Tumor necrosis factor alpha (TNF-α) is a central cytokine that drives the inflammation in RA; hence inhibition of TNF-α offers an attractive treatment strategy in RA. The introduction of TNF-α inhibitors, a class of biologic DMARDs, has dramatically changed the treatment of RA as these are highly effective therapies. Medication-related adverse events remain a major problem in health care. This is true of the TNF-α antagonists as well, with particular concerns about increased risks of infections and malignancy. Because clinical trials performed prior to medication approval are limited by the number and clinical complexity of participants and the duration of the trials, post-marketing surveillance is critical in identifying adverse events. In order to better clarify the safety issues related to the use of TNF-α inhibitors in RA, several studies using large observational registries along with pooled meta-analyses of these studies have been published. This review will summarize the data from these recent studies on the question of malignancy risk associated with TNF-α inhibitor use in RA. It is comforting that the data from these studies do not support an increased risk of cancer, except non-melanoma skin cancer, with the use of TNF-α antagonists in adults with RA. ... Read more

Inactivation of the p53 Tumor Suppressor Gene and Activation of the Ras Oncogene: Cooperative Events in Tumorigenesis

Abstract: Since the discovery of the tumor suppressor p53 and the Ras oncogene, ample data have been accumulated, describing their aberrations in human cancer and their contribution to the multistep process of tumorigenesis. Several studies have also demonstrated that these dysregulated pathways cooperate to promote malignancy. Here we review recent studies on the cooperative molecular mechanisms by which p53 inactivation and oncogenic Ras converge to enhance tumorigenesis. ... Read more

Programmed Cell Death and Apoptosis in Aging and Life Span Regulation

Abstract: Increasing evidence suggests an important role for programmed cell death (PCD) pathways in aging phenotypes across species. PCD is critical to the homeostasis of tissues maintained by cell division, for example, the blood and the lining of the gut. During aging, accumulated cellular damage and non-optimal systemic signaling can cause too little cell death (hyperproliferation and cancer), or too much cell death (tissue atrophy and ectopic cell death), thereby limiting tissue function and life span. For these reasons PCD pathways are promising targets for interventions in aging and aging-related diseases: reactivation of PCD may be beneficial in clearing cancerous and senescent cells, whereas inhibiting PCD may help prevent muscle atrophy and nervous system degeneration. ... Read more

Implementation of Biomarker-Driven Cancer Therapy: Existing Tools and Remaining Gaps

Abstract: There has been growing interest in biomarker-driven personalized cancer therapy, also known as precision medicine. Recently, dozens of molecular tests, including next generation sequencing, have been developed to detect biomarkers that have the potential to predict response of cancers to particular targeted therapies. However, detection of cancer-related biomarkers is only the first step in the battle. Deciding what therapy options to pursue can also be daunting, especially when tumors harbor more than one potentially actionable aberration. Further, different mutations/variants in a single gene may have different functional consequences, and response to targeted agents may be context dependent. However, early clinical trials with new molecular entities are increasingly conducted in a biomarker-selected fashion, and even when trials are not biomarker-selected, much effort is placed on enrolling patients onto clinical trials where they have the highest probability of response. We review available molecular tests and therapy discerning tools, including tools available for assessing functional consequences of molecular alterations and tools for finding applicable clinical trials, which exist to help bridge the gap between detection of cancer-related biomarker to the initiation of biomarker-matched targeted therapies. ... Read more

RNA Interference and Personalized Cancer Therapy

Abstract: Despite billions of dollars allocated to cancer research, cancer remains the number 2 cause of death in the United States with less than 50% of advanced cancer patients living one year following standard treatment. Cancer is a complex disease both intrinsically and in relation to its host environment. From a molecular standpoint no two cancers are the same despite histotypic similarity. As evidenced by the recent advances in molecular biology, treatment for advanced cancer is headed towards specific targeting of vulnerable signaling nodes within the reconfigured pathways created by "omic" rewiring. With advancements in proteo-genomics and the capacity of bioinformatics, complex tumor biology can now be more effectively and rapidly analyzed to discover the vulnerable high information transfer nodes within individual tumors. RNA interference (RNAi) technology, with its capability to knock down the expression of targeted genes (the vulnerable nodes), is moving into the clinic to target these nodes, which are integral to tumor maintenance, with a low risk of side-effects and to block intrinsic immunosuppressors thereby priming the tumor for immune attack. An RNAi based sequential approach, a so called "one-two punch," is being advocated comprising tumor volume reduction (ideally to minimal residual disease status) effected by integrated multi-target knockdown followed by immune activation. Examples and recent developments are provided to illustrate this highly powerful approach heralding the future of personalized cancer therapy. ... Read more

Degradation of the Transcription Factor Twist, an Oncoprotein that Promotes Cancer Metastasis

Abstract: Basic helix-loop-helix (bHLH) transcription factor Twist is one of the key inducers of epithelial to mesenchymal transition (EMT) that is a transdifferentiation program associated with embryo development and tumor metastasis. High level of Twist expression is shown to be correlated with cancer malignancy. Although Twist has been reported to be degraded by F-box and leucine-rich repeat protein 14 (FBXL14), the molecular mechanisms by which Twist levels are regulated have not been fully elucidated. In the present study, we identified Twist to be a ubiquitin substrate of β-transducin repeat-containing protein (β-TRCP), the adaptor subunit of SCFβ-TRCP (Skp1-Cul1-F-box protein) E3 ligase complex. We observed that depletion of β-TRCP leads to an accumulation of Twist protein, which could enhance tumor cell motility and cancer metastasis. Moreover, phosphorylation of Twist by inhibitor of KappaB kinase β (IKKβ) at multiple sites triggers its cytoplasmic translocation and the destruction by SCFβ-TRCP. Thus, our results provide the potential molecular mechanism of how the mesenchymal marker Twist is degraded, thereby shedding lights into regulation of the EMT, and providing the rationale for development of new therapeutic intervention to achieve better treatment outcomes in human cancer. ... Read more

Chemical-induced DNA Damage and Human Cancer Risk

Abstract: For more than 200 years human cancer induction has been known to be associated with a large variety of chemical exposures. Most exposures to chemical carcinogens occur as a result of occupation, pollution in the ambient environment, lifestyle choices, or pharmaceutical use. Scientific investigations have revealed that the majority of cancer causing chemicals, or chemical carcinogens, act through "genotoxic" or DNA damaging mechanisms, which involve covalent binding of the chemical to DNA (DNA adduct formation). Cancer-inducing exposures are typically frequent and/or chronic over years, and the accumulation of DNA damage or DNA adduct formation is considered to be a necessary requirement for tumor induction. Studies in animal models have indicated that the ability to reduce DNA damage will also result in reduction of tumor risk, leading to the hypothesis that individuals having the highest levels of DNA adducts may have an increased cancer risk, compared to individuals with the lowest levels of DNA adducts. Here we have reviewed twelve investigations showing 2- to 9-fold increased Relative Risks (RR) or Odds Ratios (OR) for cancer in (the 25% of) individuals having the highest DNA adduct levels, compared to (the 25% of) matched individuals with the lowest DNA adducts. These studies also provided preliminary evidence that multiple types of DNA adducts combined, or DNA adducts combined with other risk factors (such as infection or inflammation), may be associated with more than 10-fold higher cancer risks (RR = 34-60), compared to those found with a single carcinogen. Taken together the data suggest that a reduction in human DNA adduct level is likely to produce a reduction in human cancer risk. ... Read more

Cervical Cancer: Prevention and Treatment

Abstract: Cervical cancer is the commonest cancer cause of death among women in developing countries and efforts to prevent the disease using newer approaches and HPV vaccination need to be explored. Detection of cervical cancer at an early stage is associated with excellent survival but most women in developing countries present with advanced and often untreatable disease, with very poor survival. The ratio between incidence and mortality from cervical cancer remains very high, largely due to lack of access to appropriate anti-cancer therapies in developing countries. In developed countries with functional screening programs, cervical cancer has been rendered a relatively rare disease. Ongoing efforts to refine the characteristics of screening tests continue, as does implementation of current HPV vaccines for the primary prevention of cervical cancer. ... Read more

Tracking the Seed and Tending the Soil: Evolving Concepts in Metastatic Breast Cancer

Abstract: Metastasis, the process whereby cancer cells spread from their primary site of origin and grow in adjacent or distant sites, is the primary cause of death in cancer patients. The last 30 years has witnessed significant progress in decreasing cancer mortality rates -- largely as a result of improved screening and prevention, practical applications of cancer genomics, and less toxic, more targeted therapies. Despite these improvements, metastasis relentlessly drives mortality. The pervasive mortality from metastasis highlights the shortcomings of traditionally accepted hypotheses on the metastatic process. Historically, metastasis has been described as a unidirectional process, whereby cancer cells leave a primary tumor and seed metastasis in regional lymph nodes or distant sites. This anatomically based hypothesis has dictated much of our medical, and in particular, surgical approach to treating cancers. Alternatively, recent research indicates that metastasis is a multidirectional process whereby cancer cells can seed distant sites as well as the primary tumor itself. The multidirectional pathway of cancer cells, termed "self-seeding," has been corroborated in several experimental and clinical models. This review will evaluate the "self-seeding" hypothesis with attention both to the "seed" (cancer cells) as well as the "soil" (premetastatic niche). Increasingly, the role of the microenvironment surrounding metastases appears essential to the survival of metastatic colonies. The self-seeding model depends not only on the inherent mobility of cancer cells, but also on the supporting non-cancerous cells which enable circulating tumors cells to migrate to and survive in distant sites. The recognition that some of these non-cancerous cells include key components of the immune system has re-ignited the field of immunotherapy in cancer. One particular area of immunotherapy research, tumor entrained neutrophils, will be reviewed in more depth. Ultimately, understanding the dynamic interplay between cancer cells and the metastatic niche offers fertile ground for progress both in the treatment and prevention of metastasis. ... Read more

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