Joe B. Harford

Evidence that the pathway of transferrin receptor mRNA degradation involves an endonucleolytic cleavage within the 3' UTR and does not involve poly(A) tail shortening.

The stability of transferrin receptor (TfR) mRNA is regulated by iron availability. When a human plasma‐cytoma cell line (ARH‐77) is treated with an iron source (hemin), the TfR mRNA is destabilized and a shorter TfR RNA appears. A similar phenomenon is also observed in mouse fibroblasts expressing a previously characterized iron‐regulated human TfR mRNA (TRS‐1). In contrast, mouse cells expressing a constitutively unstable human TfR mRNA (TRS‐4) display the shorter RNA irrespective of iron treatment. These shorter RNAs found in both the hemin‐treated ARH‐77 cells and in the mouse fibroblasts are shown to be the result of a truncation within the 3′ untranslated regions of the mRNAs. The truncated RNA is generated by an endonuclease, as most clearly evidenced by the detection of the matching 3′ endonuclease product. The cleavage site of the human TfR mRNA in the mouse fibroblasts has been mapped to single nucleotide resolution to a single‐stranded region near one of the iron‐responsive elements contained in the 3′ UTR. Site‐directed mutagenesis demonstrates that the sequence surrounding the mapped endonuclease cleavage site is required for both iron‐regulated mRNA turnover and generation of the truncated degradation intermediate. The TfR mRNA does not undergo poly(A) tail shortening prior to rapid degradation since the length of the poly(A) tail does not decrease during iron‐induced destabilization. Moreover, the 3′ endonuclease cleavage product is apparently polyadenylated to the same extent as the full‐length mRNA.

Antigen Activation of Murine T Cells Induces Tyrosine Phosphorylation of a Polypeptide Associated with the T Cell Antigen Receptor

The antigen receptor complex on murine MHC class II-restricted T cells consists of disulfide-linked alpha and beta chains noncovalently associated with four additional polypeptides, two that are endoglycosaminidase F-sensitive, gp26 and gp21, and two that are endoglycosaminidase F-resistant, p25 and p16. We demonstrate here that treatment of murine T cell hybridomas with phorbol 12-myristate 13-acetate results in phosphorylation of p25 and gp21 on serine residues. However, activation of cells by antigen results in the phosphorylation of the gp21 chain and a heretofore unidentified 21 kd protein. This newly defined polypeptide, p21, is specifically immunoprecipitated with the antigen receptor complex, is endoglycosaminidase F-resistant, and is itself part of a disulfide-linked molecule. Unlike antigen-induced phosphorylation of gp21, which occurs on serine residues, phosphorylation of p21 occurs uniquely on tyrosine residues.

Guideline Implementation for Breast Healthcare in Low-Income and Middle-Income Countries Overview of the Breast Health Global Initiative Global Summit 2007

Breast cancer outcomes in low‐ and middle‐income countries (LMCs) correlate with the degree to which 1) cancers are detected at early stages, 2) newly detected cancers can be diagnosed correctly, and 3) appropriately selected multimodality treatment can be provided properly in a timely fashion. The Breast Health Global Initiative (BHGI) invited international experts to review and revise previously developed BHGI resource‐stratified guideline tables for early detection, diagnosis, treatment, and healthcare systems. Focus groups addressed specific issues in breast pathology, radiation therapy, and management of locally advanced disease. Process metrics were developed based on the priorities established in the guideline stratification. The groups indicated that cancer prevention through health behavior modification could influence breast cancer incidence in LMCs. Diagnosing breast cancer at earlier stages will reduce breast cancer mortality. Programs to promote breast self‐awareness and clinical breast examination and resource‐adapted mammographic screening are important early detection steps. Breast imaging, initially with ultrasound and, at higher resource levels with diagnostic mammography, improves preoperative diagnostic assessment and permits image‐guided needle sampling. Multimodality therapy includes surgery, radiation, and systemic therapies. Government intervention is needed to address drug‐delivery problems relating to high cost and poor access. Guideline dissemination and implementation research plays a crucial role in improving care. Adaptation of technology is needed in LMCs, especially for breast imaging, pathology, radiation therapy, and systemic treatment. Curricula for education and training in LMCs should be developed, applied, and studied in LMC‐based learning laboratories to aid information transfer of evidence‐based BHGI guidelines. Cancer 2008;113(8 suppl):2221–43. Published 2008 by the American Cancer Society.

Iron regulation of transferrin receptor mRNA levels requires iron-responsive elements and a rapid turnover determinant in the 3' untranslated region of the mRNA

Post‐transcriptional regulation of transferrin receptor mRNA levels by iron is mediated by a portion of the 3′ untranslated region (UTR) of the mRNA. We have previously shown that a 678 nucleotide fragment of the 3′UTR contains the regulatory element(s). Within this region are five RNA structures which resemble the iron‐responsive element (IRE) in the 5′ untranslated region of the ferritin mRNA which is regulated translationally by iron. The IREs from the ferritin and transferrin receptor mRNAs compete in an in vitro assay for interaction with a cytoplasmic protein; the activity of this IRE‐binding protein is dependent upon the iron status of the cells. Based on further deletion analysis reported here, the sequence required for iron regulation of the transferrin receptor have been limited to 250 nucleotides which we have produced synthetically and cloned. This sequence, which contains three IREs, is capable of producing iron‐dependent regulation of transferrin receptor levels. Removal of the three IREs from the synthetic element results in loss of iron regulation. Moreover, deletion of a single cytosine residue from each of the three IREs in the synthetic regulatory element eliminates high‐affinity binding to the IRE‐binding protein in vitro and results in low levels of iron‐independent transferrin receptor expression, consistent with production of a constitutively unstable mRNA. These data indicate that the ability of the mRNA to interact with the IRE‐binding protein is required for regulation of transferrin receptor mRNA levels by iron.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of the components of the murine T cell antigen receptor complex.

In addition to the alpha and beta chains of the MHC class II restricted antigen receptor, monoclonal anti-receptor antibodies coprecipitate four polypeptides that appear to be noncovalently associated with the alpha-beta dimer of murine T cells. Included in the murine T cell antigen receptor complex are two glycoproteins of 25 kd (gamma) and 21 kd (delta) and two nonglycosylated polypeptides of 26 kd (epsilon) and 16 kd (zeta). The epsilon chain appears to possess an intrachain disulfide bond and zeta exists in the complex as a disulfide-linked homodimer. The delta chain is phosphorylated on a serine residue in response to T cell activation with antigen. In contrast, both delta and epsilon are phosphorylated in response to treatment of the T cells with phorbol 12-myristate 13-acetate. These polypeptides may play a role in the transduction of the signal(s) in T cell activation.

Optimisation of breast cancer management in low-resource and middle-resource countries: executive summary of the Breast Health Global Initiative consensus, 2010

The purpose of the Breast Health Global Initiative (BHGI) 2010 summit was to provide a consensus analysis of breast cancer control issues and implementation strategies for low-income and middle-income countries (LMCs), where advanced stages at presentation and poor diagnostic and treatment capacities contribute to lower breast cancer survival rates than in high-income countries. Health system and patient-related barriers were identified that create common clinical scenarios in which women do not present for diagnosis until their cancer has progressed to locally advanced or metastatic stages. As countries progress to higher economic status, the rate of late presentation is expected to decrease, and diagnostic and treatment resources are expected to improve. Health-care systems in LMCs share many challenges including national or regional data collection, programme infrastructure and capacity (including appropriate equipment and drug acquisitions, and professional training and accreditation), the need for qualitative and quantitative research to support decision making, and strategies to improve patient access and compliance as well as public, health-care professional, and policy-maker awareness that breast cancer is a cost-effective, treatable disease. The biggest challenges identified for low-income countries were little community awareness that breast cancer is treatable, inadequate advanced pathology services for diagnosis and staging, and fragmented treatment options, especially for the administration of radiotherapy and the full range of systemic treatments. The biggest challenges identified for middle-resource countries were the establishment and maintenance of data registries, the coordination of multidisciplinary centres of excellence with broad outreach programmes to provide community access to cancer diagnosis and treatment, and the resource-appropriate prioritisation of breast cancer control programmes within the framework of existing, functional health-care systems.

Transcriptional regulation by iron of the gene for the transferrin receptor.

Treatment of K562 cells with desferrioxamine, a permeable iron chelator, led to an increase in the number of transferrin receptors. Increasing intracellular iron levels by treatment of cells with either human diferric transferrin or hemin lowered the level of the transferrin receptors. By using a cDNA clone of the human transferrin receptor, we showed that the changes in the levels of the receptor by iron were accompanied by alterations in the levels of the mRNA for the receptor. The rapidity of these changes indicated that the mRNA had a very short half-life. By using an in vitro transcriptional assay with isolated nuclei, we obtained evidence that this regulation occurred at the transcriptional level.

Translational repression by a complex between the iron-responsive element of ferritin mRNA and its specific cytoplasmic binding protein is position-dependent in vivo.

The interaction of ferritin mRNA is regulated by iron via the interaction of a cytoplasmic binding protein (IRE‐BP) with a specific stem‐loop structure in the 5′ untranslated region (UTR), referred to as the iron‐responsive element (IRE). A high affinity RNA‐protein complex between the IRE and the IRE‐BP functions as a repressor of translation in vivo. Translational repression appears to depend upon the position of the IRE in the 5′ UTR of the mRNA. IREs located in the 5′ untranslated region 67 nucleotides or more downstream of the 5′ terminus of the mRNA fail to mediate iron‐dependent translational regulation and give rise to constitutively derepressed transcripts. A model is proposed in which translational regulation of protein biosynthesis involves a position‐dependent interference of the IRE/IRE‐BP complex with one of the initial steps in translation initiation.

Challenges and opportunities in cancer control in Africa: a perspective from the African Organisation for Research and Training in Cancer

Sub-Saharan Africa has a disproportionate burden of disease and faces a major public-health challenge from non-communicable diseases. Although infectious diseases continue to afflict Africa, the proportion of the overall disease burden in sub-Saharan Africa attributable to cancer is rising. The region is predicted to have a greater than 85% increase in cancer burden by 2030. Approaches to minimise the burden of cancer in sub-Saharan Africa in the past few years have had little success because of low awareness of the cancer burden and a poor understanding of the potential for cancer prevention. Success will not be easy, and will need partnerships and bridges to be built across countries, economies, and professions. A strategic approach to cancer control in sub-Saharan Africa is needed to build on what works there and what is unique to the region. It should ideally be situated within strong, robust, and sustainable health-care systems that offer quality health care to all people, irrespective of their social or economic standing. However, to achieve this will need new leadership, critical thinking, investment, and understanding. We discuss the present situation in sub-Saharan Africa and propose ideas to advance cancer control in the region, including the areas of cancer awareness, advocacy, research, workforce, care, training, and funding.

Breast-cancer early detection in low-income and middle-income countries: do what you can versus one size fits all

In general, rates of breast cancer are lower in low-income and middle-income countries (LMCs) than they are in more industrialised countries of North America and Europe. This lower incidence means that screening programmes aimed at early detection in asymptomatic women would have a lower yield--ie, substantially more women would need to be examined to find a true case of breast cancer. Because the average age of breast cancer is generally younger in LMCs, it has been suggested that breast-cancer screening programmes begin at an earlier age in these settings. However, the younger average age of breast cancer is mainly driven by the age distribution of the population, and fewer older women with breast cancer, rather than by higher age-specific incidence rates in younger women. Resources in LMCs might be better used to raise awareness and encourage more women with palpable breast lumps to seek and receive treatment in a timely manner.