The molecular basis of α-thalassemia: a model for understanding human molecular genetics

Down-regulation of α-globin synthesis causes α-thalassemia with underproduction of fetal (HbF, α(2)γ(2)) and adult (HbA, α(2)β(2)) hemoglobin. This article focuses on the human α-globin cluster, which has been characterized in great depth over the past 30 years. In particular the authors describe how the α genes are normally switched on during erythropoiesis and switched off as hematopoietic stem cells commit to nonerythroid lineages. In addition, the principles by which α-globin expression may be perturbed by natural mutations that cause α-thalassemia are reviewed.     

Rapporteurs report — endocrinology and molecular biology

Over 25 years ago Bulbrooket al. [1] published initial results on the endocrine comparison of British and Japanese women, and this led him and Hayward to initiate a detailed Anglo-Japanese collaboration to determine whether there was an endocrine basis for the difference in breast cancer incidence. This study covered an age range from teenage to past the menopause. In the intervening years there have been a number of similar studies, and it seems appropriate that this meeting has provided a forum for discussing the results of these investigations.     

Medulloblastoma: what is the role of molecular genetics?

Among pediatric malignancies, medulloblastoma (MB) is one of the most common malignant tumors of the CNS. In the past few years, thanks to a multidisciplinary approach including surgery, chemo- and radiation therapy, survival has significantly improved. Despite that, a third of patients still have a low chance of being cured and long-term survivors experience severe treatment-related sequelae. MBs are usually classified according to a clinical risk stratification, based on histological features, age at diagnosis, extent of tumor resection and presence or absence of metastases. However, these clinical variables have recently been reported to be poor for defining risk-related disease. Retrospective studies have identified histological or biological factors that have distinct roles in prognosis. As several pathways have been discovered to be involved in MB pathogenesis, they should be taken into account to more accurately stratify patients and their treatment and to develop innovative therapies.     

Renal cell carcinoma bone metastasis—elucidating the molecular targets

The development of bone metastasis from renal cell carcinoma (RCC) signals a transition to a terminal state for the patient with previously isolated disease. These patients may suffer the morbidity of severe, persistent pain, pathologic fractures, and spinal compression from vertebral metastasis before they succumb to their cancer. Although recent advancements have been made in the understanding of breast and prostate bone metastasis, there has been less knowledge in the area of metastatic RCC to the skeleton. This particular cancer in bone remains relatively resistant to standard forms of treatment such as radiation and chemotherapy. A better understanding of the biology of RCC bone metastasis is critically needed in order to improve treatment. Bone-derived cell lines and an experimental animal model have been developed in order to explore the relevant mechanisms of how RCC cells survive within and destroy the bone. This review will focus on the growth factor signaling pathways most important for the RCC-stimulated osteoclast-mediated bone destruction, namely the epidermal growth factor receptor (EGF-R) and transforming growth factor-β receptor (TGF-βR) pathways. By inhibiting these receptors, growth of RCC within the bone is decreased which, directly or indirectly, decreases bone destruction.     

Papillary lesions of the breast: a molecular progression?

Summary Introduction. Breast papillary lesions represent a heterogeneous group of tumors ranging from benign to malignant, including several intermediate forms. Malignant papillary tumors are rare and their molecular characterization is still limited. A few studies pointed to the presence of specific genetic alterations that could be relevant both for diagnostic purposes and to elucidate tumour development and progression. In order to look into the issue, we compared LOH relative frequencies of four microsatellite markers located on chromosome 16 in a set of morphologically different papillary breast lesions. LOH at TP53 locus was also analyzed throughout lesions. Materials and methods. Fifteen cases were analyzed. Sections including a malignant papillary lesion, a benign lesion (when available), and normal breast tissue were selected. Fifteen malignant and twelve benign areas were microdissected using the Leica laser microdissection system (AS LMD). After DNA extraction samples were tested for the following markers: TP53, D16S423, D16S310, DS163210 and D16S476, and analyzed on ABI PRISM 3100 (Applied Biosystems, Foster city CA). Results. Fourteen malignant lesions and twelve paired benign areas appeared to be informative for at least one of the four markers on chromosome 16. In particular, LOH at loci 16p13 and 16q21 was detected in both benign and malignant lesions, whereas LOH at locus 16q23 was limited to malignant lesions. Nine malignant and seven benign lesions were informative for LOH at TP53 locus, that was found to be significantly associated (p=0.01) with the malignant phenotype. Conclusions. Our data suggest an involvement of chromosome 16 mutations in the early steps of breast papillary tumorigenesis. TP53 deletion and possibly LOH at 16q23 appear to play a role as progression factors, being they significantly associated with malignant transformation of breast papilloma.     

Can axillary dissection be avoided by improved molecular biological diagnosis?

Axillary dissection is presently a routine staging procedure in the management of breast cancer. The use of adjuvant systemic treatment is largely based on the diagnosis of axillary metastases. Routine axillary dissection leads to acute and chronic side-effects in a large proportion of patients. The sentinel node technique is presently explored with the aim of decreasing the need for standard axillary dissection. A complementary way forward is to analyse the primary breast cancer for molecular markers with prognostic significance with reference to the risk for metastatic capacity and thereby obtain a 'biological staging' and identify those patients in need of systemic adjuvant therapy. A large number of molecular biological factors have been shown to have prognostic significance in breast cancer e.g. c-erbB-2, p53, uPA, PAI-1 and VEGF. This article reviews the expression of these and other factors in the primary breast cancers in relation to the risk for axillary and systemic metastatic disease, with the long-term aim of excluding routine axillary dissection.     

The Potential for molecular therapeutic targets in Ewing’s sarcoma

Opinion statement Ewing’s sarcoma is an uncompromising tumor of children and young adults. Before the introduction of chemotherapy for Ewing’s sarcoma, nearly all patients succumbed to their disease, even with highly aggressive approaches to local control. The realization that most patients have micrometastatic disease at presentation, and the identification of active chemotherapeutic agents for this tumor, have resulted in significant improvements in patient survival. Modern therapy for Ewing’s sarcoma combines highdose chemotherapy for systemic control of disease, with advanced surgical and/or radiation therapeutic approaches for local control. Current therapy remains imperfect. Despite optimal management, the cure rate for localized disease is only approximately 70%, whereas the cure rate for metastatic disease at presentation is less than 30%. Patients who experience long-term disease-free survival are at risk for significant side effects of therapy, including infertility, limb dysfunction, and an increased risk for second malignancies. More effective and less toxic therapies are needed. This report presents an overview of dysregulated molecular pathways in Ewing’s sarcoma and highlights the possibility that they may serve as therapeutic targets for the disease. Although a great deal of additional investigation is required before most of these approaches can be assessed in the clinic, we think that these potential new targets offer a great deal of hope for patients with Ewing’s sarcoma.     

New specific molecular targets for radio‐chemotherapy of rectal cancer

Patients with locally advanced rectal cancer often receive preoperative radio‐chemotherapy (RCT). The mechanisms of tumour response to radiotherapy are not understood. The aim of this study was to identify the effects of RCT on gene expression in rectal tumour and normal rectal tissue. For that purpose tissue samples from 21 patients with resectable adenocarcinomas were collected for use in whole genome‐microarray based gene expression analysis. A factorial experimental design allowed us to determine the effect of RCT on tumour tissue alone by removing the effect of radiation on normal tissue. This resulted in 1327 differentially expressed genes in tumour tissue with p<0.05. In addition to known markers for radio‐chemotherapy, a Gene Set Enrichment Analysis (GSEA) showed a significant enrichment in gene sets associated with cell adhesion and leukocyte transendothelial migration. The profound change of cell adhesion molecule expression in rectal tumour tissue could either increase the risk of metastasis, or decrease the tumour''s invasive potential.     

The molecular landscape of the normal human breast – defining normal

A key approach in understanding how breast cancer can occur is to determine the regulatory pathways at play in the normal breast and to identify precisely the normal developmental mechanisms subverted during early breast cancer progression. Using normal human breast tissue samples, Pardo and colleagues have identified the gene targets and pathways displaying fluctuating expression as a consequence of the menstrual cycle. Detailed characterization of how the human breast functions in its normal state, and how this may be perturbed at its earliest point, will provide a critical step toward the prevention of breast cancer.Although breast cancer mortality rates have decreased over recent years, incidence rates continue to increase. There is broad acceptance that strategies focused on disease prevention and identification of early malignant change are most likely to contribute to real improvements in breast cancer incidence. Understanding the molecular landscape of the normal breast is a critical step in developing such approaches. The article by Pardo and colleagues [1] in the previous issue of Breast Cancer Research contributes an exciting new resource that addresses that goal.Recent advances in whole-genome sequencing and expression profiling have profoundly expanded our understanding of the malignant landscape [2,3], yet the combined complement of genes expressed in cancer tissue at the time of sampling fail to provide insight into biological pathways involved in carcinogenesis. Defining the molecular events in the normal breast which contribute to the formation of a breast tumor remains elusive, and the prevention of breast cancer at its earliest stages continues to be a holy grail in breast cancer management. Although it has long been known that the hormonal milieu of the breast influences normal tissue development [4] and that exposure to exogenous hormone analogues in hormone replacement therapy and oral contraceptives contributes adversely to breast cancer risk [5,6], there is a paucity of information on the molecular events underlying this influence in humans.Understanding regulatory pathways at play in the normal breast and the precise identification of normal developmental mechanisms subverted during early breast cancer progression are key steps toward prevention. Owing partly to a lack of appropriate models, much of our current understanding of normal breast development derives from studies in animals and, remarkably, details of how the normal human breast functions remain largely unknown. A landmark study by Longacre and Bartow [7] in 1986 described the morphological changes occurring in the normal breast during the menstrual cycle. In that study, histologic features, including mitoses, were described in a cohort of 75 premenopausal normal breast autopsy specimens, matched exactly to menstrual cycle phase by endometrial dating. The investigators discovered a striking correlation between menstrual cycle phase and proliferation, with the number of mitoses peaking with higher levels of circulating progesterone. This study was the first to directly implicate progesterone in driving cyclical development in the normal breast and is consistent with key epidemiological findings reported by Pike and colleagues [8], who postulated that this increased mitotic activity during the luteal phase is associated with a transient increase in breast cancer risk.The article by Pardo and colleagues [1] takes the approach of Longacre and Bartow to the molecular level, resulting in an interesting series of discoveries, which both confirm and extend the findings of the 1986 study. A major strength of this new study is the utilization of normal breast tissue samples from 20 premenopausal donors to the Susan G. Komen for the Cure Tissue Bank at the IU Simon Cancer Center (KTB). By laser capture microdissecting the ductal epithelium of these samples followed by next-generation RNA sequencing, they identified the gene targets and pathways displaying fluctuating expression during the menstrual cycle in the normal human breast.They demonstrated that 255 genes were differentially expressed between the follicular and luteal phases of the menstrual cycle. The vast majority of these (87%) displayed higher expression during the luteal phase, when serum concentrations of progesterone are higher. Significantly upregulated targets during the luteal phase were enriched for functions relating to cell cycle, cellular organization and repair, and DNA replication, recombination, and repair. These findings confirm the proliferative role of progesterone demonstrated in models of normal human breast [9] and in the murine mammary gland [10]. Data derived from mouse models have shown that progesterone regulates the mammary stem cell compartment during pregnancy and the reproductive cycle [11,12], a mechanism suggested to account for the increased window of susceptibility to transformation at these times.Interestingly, many of the proliferative targets that Pardo and colleagues identified to be upregulated during the luteal phase are also associated with overexpression in breast cancer. Could dysregulation of these particular gene sets similarly represent a transient period of increased susceptibility to tumorigenesis during the luteal phase in the human breast? As this study shows that the genetic signature of the breast epithelium of women taking hormonal contraception resembles that of a continuous luteal phase, the altered regulation of these gene sets could also provide a potential mechanism to account for the increased breast cancer risk associated with progestin-containing oral contraception [6]. Moreover, progesterone regulation of these gene sets may underlie its hypothesized role as a promoter of malignant lesions in the breast [13-15].As healthy women are frequently exposed to changes in their hormonal milieu, it will now be critical to determine whether this is indeed the case. Identification of such specific gene sets and pathways which contribute to increased breast tumor susceptibility could then provide novel indicators of breast cancer risk, prognosis, or treatment options (or a combination of these) and will be valuable in the development of new safer progestational agents. Moreover, as we now know that it is likely that only a subset of epithelial cells in the breast possess the potential to give rise to malignancies, these gene sets may represent key tools in the identification and isolation of such subpopulations.Through the altruistic tissue donations by healthy women to the KTB, this unique repository of normal breast tissue and matched serum, plasma, and DNA is the largest of its kind in the world. The challenges in studying cancer initiation and progression in humans in vivo present a critical imperative for normal human tissue resources, such as the KTB, to facilitate investigation into the complete evolution of breast cancer and, indeed, any type of cancer. That is, in order to determine what is abnormal, we need to fully define what is normal.     

Is molecular profiling ready for use in clinical decision making?

Molecular profiling, the classification of tissue or other specimens for diagnostic, prognostic, and predictive purposes based on multiple gene expression, is a technology that holds major promise for optimizing the management of patients with cancer. However, the use of these tests for clinical decision making presents many challenges to overcome. Assay development and data analysis in this field have been largely exploratory, and leave numerous possibilities for the introduction of bias. Standardization of profiles remains the exception. Classifier performance is usually overinterpreted by presenting the results as p-values or multiplicative effects (e.g., relative risks), while the absolute sensitivity and specificity of classification remain modest at best, especially when tested in large validation samples. Validation has often been done with suboptimal attention to methodology and protection from bias. The postulated classifier performance may be inflated compared to what these profiles can achieve. With the exception of breast cancer, we have little evidence about the incremental discrimination that molecular profiles can provide versus classic risk factors alone. Clinical trials have started to evaluate the utility of using molecular profiles for breast cancer management. Until we obtain data from these trials, the impact of these tests and the net benefit under real-life settings remain unknown. Optimal incorporation into clinical practice is not straightforward. Finally, cost-effectiveness is difficult to appreciate until these other challenges are addressed. Overall, molecular profiling is a fascinating and promising technology, but its incorporation into clinical decision making requires careful planning and robust evidence.     

Familial colorectal cancer type X syndrome: two distinct molecular entities?

In a fraction of families fulfilling the Amsterdam criteria for hereditary non-polyposis colorectal cancer, colorectal cancers are microsatellite stable and DNA mismatch repair gene (MMR) mutations are not found. These families were designated as familial colorectal cancer type X (FCCTX). We aimed to characterise a group of FCCTX families defined by the Amsterdam criteria and MSS tumours at clinical and molecular level. Twenty-four tumours from 15 FCCTX families were analysed for loss of known tumour suppressor gene (TSG) loci (APC, TP53, SMAD4 and DCC), MGMT and MMR genes promoter methylation, and also APC and KRAS somatic mutations. FCCTX families presented specific clinical features: absence of endometrial tumours, high adenoma/carcinoma ratio (1.91) and prevalence of rectal cancers (13/27, 48%). New molecular features were found: the majority of FCCTX tumours (13/18; 72%) presented TSG loss. TSG loss positive tumours presented frequent APC and KRAS somatic mutations and MGMT methylation [10/13 (77%), 7/13 (54%) and 6/11 (54%), respectively]. In TSG loss negative tumours (5/18; 28%), the same molecular events were found in 2/5 (40%), 2/5 (40%) and 1/3 (33%) tumours, respectively. Transition mutations in KRAS were more frequent among MGMT methylated tumours than in unmethylated [5/8 (63%) vs. 1/10 (10%), P?=?0.03]. Although sharing similar clinical features, at least two different molecular entities should exist among FCCTX families, one whose tumours present frequent TSG loss, APC and KRAS somatic mutations, and MGMT promoter methylation, and a second, lesser predominant, with no evidence of TSG loss and rarely presenting promoter methylation.     

RNA polymerase – An important molecular target of triptolide in cancer cells

Triptolide, a diterpenoid triepoxide, is the key biological component of Tripterygium wilfordii Hook. f. which was used in traditional Chinese medicine for centuries to treat inflammation and autoimmune diseases. Triptolide has shown potent activity in not only anti-inflammation and immune modulation, but also antiproliferative and proapoptotic activity in many different types of cancer cells. However, for a long time, the precise molecular target(s) of triptolide have remained elusive. Recently, several groups discovered that triptolide inhibited the activity of RNA polymerase. This review will focus on these breakthrough findings about the molecular target of triptolide and its implications for targeted-cancer therapeutics.     

Extraneuraxial metastases in medulloblastoma: is histology and molecular biology important?

Journal of Neuro-Oncology - Leptomeningeal metastases are a late manifestation of systemic cancer which affects up to 10% of patients with solid tumors. Prognosis is poor, and overall survival at...     

TWEAK and Fn14: New molecular targets for cancer therapy?

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) is a member of the tumor necrosis factor (TNF) superfamily of structurally related cytokines. Full-length, membrane-anchored TWEAK can be found on the surface of many cell types and a smaller, biologically active form, generated via proteolytic processing, has also been detected in the extracellular milieu. TWEAK acts via binding to a recently identified TNF receptor superfamily member named fibroblast growth factor-inducible 14 (Fn14). It has been demonstrated that TWEAK binding to the Fn14 receptor, or constitutive Fn14 overexpression, activates the nuclear factor-kappaB signaling pathway, which is known to play an important role in immune and inflammatory processes, oncogenesis, and cancer therapy resistance. In this article, we review recent studies indicating that TWEAK and Fn14 may be potential regulators of human tumorigenesis.     

Prognostic impact of molecular markers in a series of 220 primary glioblastomas

BACKGROUND： In contrast to ofigodendrogliomas, molecular predictors of prognosis have not been consistently found in glioblastomas. However, genetic studies show that glioblastomas consist of several genetic subtypes and raise the possibility that molecular alterations could be predictive of survival. METHODS： A search for loss of heterozygosity （LOH） on chromosome 1p, 9p, 10q, 19q, EGFR （epidermal growth factor receptor）, CDK4, and MDM2 （mouse double minute） amplifications, CDKN2A （INK4A/ARF） homozygous deletions, p53 expression, was performed in a series of 220 primary glioblastomas.