Tumour Infiltrating Lymphocytes (TILs) and immune composition in breast cancer patients from Kenya: Spatial distributions and associations with risk factors and tumour characteristics.

BACKGROUND: The immune landscape of breast cancer (BC) in patients from Sub Saharan Africa is understudied. Our aims were to describe the distribution of Tumour Infiltrating Lymphocytes (TILs) within the intratumoural stroma (sTILs) and the leading/invasive edge stroma (LE-TILs), and to evaluate TILs across BC subtypes with established risk factors and clinical characteristics in Kenyan women. METHODS: Visual quantification of sTILs and LE-TILs were performed on Haematoxylin and eosin -stained pathologically confirmed BC cases based on the International TIL working group guidelines. Tissue Microarrays were constructed and stained with immunohistochemistry (IHC) for CD3, CD4, CD8, CD68, CD20, and FOXP3. Linear and logistic regression models were used to assess associations between risk factors and tumour features with IHC markers and total TILs, after adjusting for other covariates. RESULTS: A total of 226 invasive BC cases were included. Overall, LE-TIL (mean = 27.9, SD = 24.5) proportions were significantly higher than sTIL (mean = 13.5, SD = 15.8). Both sTILs and LE- TILs were predominantly composed of CD3, CD8, and CD68. We found higher TILs to be associated with high KI67/high grade and aggressive tumour subtypes, although these associations varied by TIL locations. Older age at menarche (≥ 15 vs. < 15 years) was associated with higher CD3 (OR: 2.06, 95%CI:1.26-3.37), but only for the intra-tumour stroma. CONCLUSION: The TIL enrichment in more aggressive BCs is similar to previously published data in other populations. The distinct associations of sTIL/LE-TIL measures with most examined factors highlight the importance of spatial TIL evaluations in future studies.

Breast cancer risk factors in relation to molecular subtypes in breast cancer patients from Kenya.

BACKGROUND: Few studies have investigated risk factor heterogeneity by molecular subtypes in indigenous African populations where prevalence of traditional breast cancer (BC) risk factors, genetic background, and environmental exposures show marked differences compared to European ancestry populations. METHODS: We conducted a case-only analysis of 838 pathologically confirmed BC cases recruited from 5 groups of public, faith-based, and private institutions across Kenya between March 2012 to May 2015. Centralized pathology review and immunohistochemistry (IHC) for key markers (ER, PR, HER2, EGFR, CK5-6, and Ki67) was performed to define subtypes. Risk factor data was collected at time of diagnosis through a questionnaire. Multivariable polytomous logistic regression models were used to determine associations between BC risk factors and tumor molecular subtypes, adjusted for clinical characteristics and risk factors. RESULTS: The median age at menarche and first pregnancy were 14 and 21 years, median number of children was 3, and breastfeeding duration was 62 months per child. Distribution of molecular subtypes for luminal A, luminal B, HER2-enriched, and triple negative (TN) breast cancers was 34.8%, 35.8%, 10.7%, and 18.6%, respectively. After adjusting for covariates, compared to patients with ER-positive tumors, ER-negative patients were more likely to have higher parity (OR = 2.03, 95% CI = (1.11, 3.72), p = 0.021, comparing ≥ 5 to ≤ 2 children). Compared to patients with luminal A tumors, luminal B patients were more likely to have lower parity (OR = 0.45, 95% CI = 0.23, 0.87, p = 0.018, comparing ≥ 5 to ≤ 2 children); HER2-enriched patients were less likely to be obese (OR = 0.36, 95% CI = 0.16, 0.81, p = 0.013) or older age at menopause (OR = 0.38, 95% CI = 0.15, 0.997, p = 0.049). Body mass index (BMI), either overall or by menopausal status, did not vary significantly by ER status. Overall, cumulative or average breastfeeding duration did not vary significantly across subtypes. CONCLUSIONS: In Kenya, we found associations between parity-related risk factors and ER status consistent with observations in European ancestry populations, but differing associations with BMI and breastfeeding. Inclusion of diverse populations in cancer etiology studies is needed to develop population and subtype-specific risk prediction/prevention strategies.

The Role of Tumor Microenvironment in Chemoresistance: 3D Extracellular Matrices as Accomplices.

BACKGROUND: The functional interplay between tumor cells and their adjacent stroma has been suggested to play crucial roles in the initiation and progression of tumors and the effectiveness of chemotherapy. The extracellular matrix (ECM), a complex network of extracellular proteins, provides both physical and chemicals cues necessary for cell proliferation, survival, and migration. Understanding how ECM composition and biomechanical properties affect cancer progression and response to chemotherapeutic drugs is vital to the development of targeted treatments. METHODS: 3D cell-derived-ECMs and esophageal cancer cell lines were used as a model to investigate the effect of ECM proteins on esophageal cancer cell lines response to chemotherapeutics. Immunohistochemical and qRT-PCR evaluation of ECM proteins and integrin gene expression was done on clinical esophageal squamous cell carcinoma biopsies. Esophageal cancer cell lines (WHCO1, WHCO5, WHCO6, KYSE180, KYSE 450 and KYSE 520) were cultured on decellularised ECMs (fibroblasts-derived ECM; cancer cell-derived ECM; combinatorial-ECM) and treated with 0.1% Dimethyl sulfoxide (DMSO), 4.2 µM cisplatin, 3.5 µM 5-fluorouracil and 2.5 µM epirubicin for 24 h. Cell proliferation, cell cycle progression, colony formation, apoptosis, migration and activation of signaling pathways were used as our study endpoints. RESULTS: The expression of collagens, fibronectin and laminins was significantly increased in esophageal squamous cell carcinomas (ESCC) tumor samples compared to the corresponding normal tissue. Decellularised ECMs abrogated the effect of drugs on cancer cell cycling, proliferation and reduced drug induced apoptosis by 20⁻60% that of those plated on plastic. The mitogen-activated protein kinase-extracellular signal-regulated kinase (MEK-ERK) and phosphoinositide 3-kinase-protein kinase B (PI3K/Akt) signaling pathways were upregulated in the presence of the ECMs. Furthermore, our data show that concomitant addition of chemotherapeutic drugs and the use of collagen- and fibronectin-deficient ECMs through siRNA inhibition synergistically increased cancer cell sensitivity to drugs by 30⁻50%, and reduced colony formation and cancer cell migration. CONCLUSION: Our study shows that ECM proteins play a key role in the response of cancer cells to chemotherapy and suggest that targeting ECM proteins can be an effective therapeutic strategy against chemoresistant tumors.

TNF-dependent regulation and activation of innate immune cells are essential for host protection against cerebral tuberculosis.

BACKGROUND: Tuberculosis (TB) affects one third of the global population, and TB of the central nervous system (CNS-TB) is the most severe form of tuberculosis which often associates with high mortality. The pro-inflammatory cytokine tumour necrosis factor (TNF) plays a critical role in the initial and long-term host immune protection against Mycobacterium tuberculosis (M. tuberculosis) which involves the activation of innate immune cells and structure maintenance of granulomas. However, the contribution of TNF, in particular neuron-derived TNF, in the control of cerebral M. tuberculosis infection and its protective immune responses in the CNS were not clear. METHODS: We generated neuron-specific TNF-deficient (NsTNF(-/-)) mice and compared outcomes of disease against TNF(f/f) control and global TNF(-/-) mice. Mycobacterial burden in brains, lungs and spleens were compared, and cerebral pathology and cellular contributions analysed by microscopy and flow cytometry after M. tuberculosis infection. Activation of innate immune cells was measured by flow cytometry and cell function assessed by cytokine and chemokine quantification using enzyme-linked immunosorbent assay (ELISA). RESULTS: Intracerebral M. tuberculosis infection of TNF(-/-) mice rendered animals highly susceptible, accompanied by uncontrolled bacilli replication and eventual mortality. In contrast, NsTNF(-/-) mice were resistant to infection and presented with a phenotype similar to that in TNF(f/f) control mice. Impaired immunity in TNF(-/-) mice was associated with altered cytokine and chemokine synthesis in the brain and characterised by a reduced number of activated innate immune cells. Brain pathology reflected enhanced inflammation dominated by neutrophil influx. CONCLUSION: Our data show that neuron-derived TNF has a limited role in immune responses, but overall TNF production is necessary for protective immunity against CNS-TB.

Copy Number Analysis of the DLX4 and ERBB2 Genes in South African Breast Cancer Patients.

Breast cancer is one of the main causes of cancer death among South African women. Although several risk factors can be attributed to the observed high mortality rate, the biology of the tumors is not extensively investigated. Copy number gain of the DLX4 homeobox gene has been observed in breast cancer in association with poor prognosis and specific racial groups. Therefore, we aimed to assess the copy number and prognostic role of DLX4 in breast cancer from South African patients. Due to the co-location of ERBB2 and DLX4 in the 17q21 region, its copy number was also evaluated. Our results in the analysis of 66 cases demonstrated copy number gains of DLX4 and ERBB2 in 24.1 and 29.7% of the cases, respectively. Linear regression analysis showed no dependency between the copy number alterations in these genes. Although not significant, patients with DLX4 and ERBB2 gains presented a higher frequency of advanced-grade tumors. In addition, copy number alterations of these genes were not significantly differently observed in the 3 main racial groups of the Western Cape population: Colored, White, and Black. These findings indicate that gains of DLX4 and ERBB2 occur in South African breast cancer patients irrespectively of their race and factors known to influence prognosis.

Gene of the month: H3F3A and H3F3B.

H3F3A and H3F3B genes are located at 1q42.12 and 17q25.1, respectively, and encode identical H3.3 core histone proteins which form part of the histone hetero-octamer complex. Histones function by packaging DNA into small units, the nucleosome, and are highly susceptible to epigenetic post-translational modification. H3 K27 mutations have been shown to inhibit the polycomb repressive complex 2, which is normally involved in epigenetic gene silencing. Mutations in H3F3A and H3F3B are increasingly recognised in a variety of solid tumours. Point mutations in H3F3A have been described in giant cell tumour of bone and paediatric-type diffuse high-grade gliomas. Mutations in H3F3B have been described in chondroblastoma. Loss of trimethylation of H3 K27 is characteristic of most sporadic and radiation-associated malignant peripheral nerve sheath tumours. Immunohistochemistry with a variety of novel antibodies directed against specific mutations, as well as loss of H3K27me3 staining, may be useful in specific settings and in diagnostically challenging cases.

Plasmablastic lymphomas show restricted EBV latency profile and MYC gene aberrations.

The pathogenesis of plasmablastic lymphoma (PBL) involves the Epstein-Barr virus (EBV), human immunodeficiency virus (HIV), and MYC gene aberrations. We aimed to determine the EBV latent infection pattern and frequency of MYC gene aberrations in PBLs. Immunohistochemistry was performed using antibodies for EBNA1, EBNA2, and LMP1 while fluorescence in situ hybridization was performed using a MYC probe. The patient cohort comprised 49 adult cases (44 were HIV-positive and three were HIV-negative). Forty-one cases were EBV-positive with 11 EBNA1-positive cases, all cases EBNA2-negative, and four LMP1-positive cases. Latency 0 was determined in 29 cases, latency I in eight cases, and latency II in four cases. The MYC gene was rearranged in eight cases, showed copy number alterations in 11 cases and, no rearrangement in 11 cases. This is the largest cohort of PBLs from South Africa to show a predominantly restricted EBV latency pattern with MYC gene aberrations as a common finding.

Carbonic anhydrase IX: a regulator of pH and participant in carcinogenesis.

Carbonic anhydrase IX (CAIX) is a transmembrane metalloenzyme which is upregulated in tumour cells under hypoxic conditions. CAIX expression is induced by the accumulation of hypoxia-inducible factor-1α and has several downstream effects, including acidification of the extracellular pH, loss of cellular adhesion and increased tumour cell migration. CAIX is upregulated in a variety of solid organ tumours and has prognostic implications. High CAIX protein expression is a marker of poor prognosis in breast, lung, ovarian and bladder carcinomas. Conversely, low expression is an indicator of poor prognosis in clear cell renal cell carcinoma (CCRCC). CAIX immunohistochemistry is useful diagnostically to identify metastatic CCRCC, and the recently recognised clear cell papillary renal cell carcinoma. There is much interest in targeting CAIX with monoclonal antibodies and small molecule inhibitors. There are several small molecule inhibitors under development which have shown promising results in clinical trials. In this paper, we provide an overview of the role of CAIX in tumourigenesis and outline its use as a prognostic, diagnostic and therapeutic biomarker.

Syphilitic Pulmonary Inflammatory Pseudotumor: A Diagnostic Challenge.

A 46-year-old man presented with nonproductive cough and lower limb swelling. Chest radiograph showed a left lower lobe lung mass and multiple subpleural nodules. Other investigations revealed that he had nephrotic syndrome. Core biopsies of the left lower lobe lung mass showed features of inflammatory pseudotumor with endarteritis obliterans and a lymphoplasmacytic infiltrate. Immunohistochemical stain for Treponema pallidum was positive. Resolution of the lung mass and nephrotic syndrome was achieved after treatment with intramuscular benzathine benzylpenicillin. The differential diagnosis of pulmonary inflammatory pseudotumor, manifestations of pulmonary syphilis, and a literature review of secondary syphilis of the lung are discussed.

Inflammatory leiomyosarcoma of the head and neck: Case report.

INTRODUCTION AND IMPORTANCE: Primary sarcomas in the head and neck region are rare. Inflammatory leiomyosarcoma was first described in 1995. The case reported herein is the first reported inflammatory leiomyosarcoma occurring in the head and neck. PRESENTATION OF CASE: A 37-year-old male presented with a long history of an asymptomatic slowly enlarging neck mass. Examination revealed a firm mass in the lower third of the right sternocleidomastoid muscle. Computerized tomography and magnetic resonance imaging showed a lobulated, well-circumscribed tumour with malignant features. A wide local excision was performed and histopathological examination confirmed an inflammatory leiomyosarcoma. DISCUSSION: Inflammatory leiomyosarcoma is a recently described peculiar soft tissue tumour with histological features overlapping conventional leiomyosarcoma, and dense lymphocytic inflammation and immunohistochemical reactivity for both smooth and skeletal muscle markers. These are indolent tumours and wide local excision is curative. CONCLUSION: This case highlights the importance of considering primary sarcomas in the differential diagnosis of asymptomatic head and neck masses.

Targeting the oncogenic TBX3:nucleolin complex to treat multiple sarcoma subtypes.

Sarcomas are diverse cancers of mesenchymal origin, with compromised clinical management caused by insufficient diagnostic biomarkers and limited treatment options. The transcription factor TBX3 is upregulated in a diverse range of sarcoma subtypes, where it plays a direct oncogenic role, and it may thus represent a novel therapeutic target. To identify versatile ways to target TBX3, we performed affinity purification coupled by mass spectrometry to identify putative TBX3 protein cofactors that regulate its oncogenic activity in sarcomas. Here we identify and validate the multifunctional phosphoprotein nucleolin as a TBX3 cofactor. We show that nucleolin is co-expressed with TBX3 in several sarcoma subtypes and their expression levels positively correlate in sarcoma patients which are associated with poor prognosis. Furthermore, we demonstrate that nucleolin and TBX3 interact in chondrosarcoma, liposarcoma and rhabdomyosarcoma cells where they act together to enhance proliferation and migration and regulate a common set of tumor suppressor genes. Importantly, the nucleolin targeting aptamer, AS1411, exhibits selective anti-cancer activity in these cells and mislocalizes TBX3 and nucleolin to the cytoplasm which correlates with the re-expression of the TBX3/nucleolin target tumor suppressors CDKN1A (p21CIP1) and CDKN2A (p14ARF). Our findings provide the first evidence that TBX3 requires nucleolin to promote features of sarcomagenesis and that disruption of the oncogenic TBX3-nucleolin interaction by AS1411 may be a novel approach for treating sarcomas.

IL-4R{alpha}-responsive smooth muscle cells increase intestinal hypercontractility and contribute to resistance during acute Schistosomiasis.

Interleukin-(IL)-4 and IL-13 signal through heterodimeric receptors containing a common IL-4 receptor-alpha (IL-4Ralpha) subunit, which is important for protection against helminth infections, including schistosomiasis. Previous studies demonstrated important roles for IL-4Ralpha-responsive hematopoietic cells, including T cells and macrophages in schistosomiasis. In this study, we examined the role of IL-4Ralpha responsiveness by nonhematopoietic smooth muscle cells during experimental acute murine schistosomiasis. Comparative Schistosoma mansoni infection studies with smooth muscle cell-specific IL-4Ralpha-deficient (SM-MHC(cre)IL-4Ralpha(-/flox)) mice, heterozygous control (IL-4Ralpha(-/flox)) mice, and global IL-4Ralpha-deficient (IL-4Ralpha(-/-)) mice were conducted. S. mansoni-infected SM-MHC(cre)IL-4Ralpha(-/flox) mice showed increased weight loss and earlier mortalities compared with IL-4Ralpha(-/flox) mice, despite comparable T(H)2/type 2 immune responses. In contrast to highly susceptible IL-4Ralpha-deficient mice, increased susceptibility in SM-MHC(cre)IL-4Ralpha(-/flox) mice was not accompanied by intestinal tissue damage and subsequent sepsis. However, both susceptible mutant mouse strains failed to efficiently expel eggs, demonstrated by egg reduction in the feces compared with control mice. Reduced egg expulsion was accompanied by impaired IL-4/IL-13-mediated hypercontractile intestinal responses, which was present in the more resistant control mice. Together, we conclude that IL-4Ralpha responsiveness by smooth muscle cells and subsequent IL-4- and IL-13-mediated hypercontractility are required for host protection during acute schistosomiasis to efficiently expel S. mansoni eggs and to prevent premature mortality.

Vaccinia virus complement control protein (VCP) improves kidney structure and function following ischemia/reperfusion injury in rats.

Renal transplantation is often confronted with ischemia reperfusion (I/R) injury that accounts for a delayed recovery of the graft. This surgically and biologically induced injury often results in activation of the complement system. The vaccinia virus complement control protein (VCP) down-regulates both the classical and alternative complement pathways by preventing the formation of C3b, a component where both pathways converge. The aim of the study was to investigate the effect of VCP on renal I/R injury. Long Evans rats were subjected to laparotomy, mobilization of the right kidney in unilateral ischemia, and both kidneys in bilateral ischemia. The renal arteries were clamped for 60 min followed by 24 h reperfusion time. The animals were randomly allocated to receive recombinant VCP (rVCP), natural VCP, and humanized recombinant VCP (hrVCP) combination, vehicle (PBS), or sham group. Blood samples were collected for biochemical studies, and the kidneys were removed for histopathologic and immunohistochemical studies. The biochemical studies in the bilateral ischemia showed that the PBS group displayed 1.5-fold and 5-fold increases in the urea and creatinine concentrations, respectively, compared with the VCP/hrVCP groups. In both models, the histopathologic study revealed focal necrosis of the tubular epithelial cells in the rVCP or VCP/hrVCP treated animals compared with the diffuse and markedly elevated field scores in the PBS controls. The immunohistochemical study showed significant C3 deposition in the renal tubules of the PBS controls compared with the rVCP or VCP/hrVCP groups, suggesting that rVCP, VCP/hrVCP reduced I/R injury by inhibiting the biosynthesis of C3.

Gene of the month: IDH1.

Isocitrate dehydrogenase 1 (IDH1) encodes a protein which catalyses the oxidative decarboxylation of isocitrate to α-ketoglutarate. Mutant IDH1 favours the production of 2-hydroxyglutarate, an oncometabolite with multiple downstream effects which promote tumourigenesis. IDH1 mutations have been described in a number of neoplasms most notably low-grade diffuse gliomas, conventional central and periosteal cartilaginous tumours and cytogenetically normal acute myeloid leukaemia. Post zygotic somatic mutations of IDH1 characterise the majority of cases of Ollier disease and Maffucci syndrome. IDH1 mutations are uncommon in epithelial neoplasia but have been described in cholangiocarcinoma.

Gene of the month: BCOR.

BCL-6 transcriptional corepressor (BCOR) gene is located at Xp11.4 and encodes a protein which is involved in transcriptional repression in association with BCL-6 and epigenetic silencing through polycomb repressive complex 1 (PRC1). BCOR mutations are being identified in an increasing number of tumours which are diverse in their anatomical location and clinical setting. Interestingly, these tumours share similar and overlapping histological features, namely small round blue cell morphology and a myxoid background with delicate capillary channels. Clear cell sarcoma of the kidney, primitive myxoid mesenchymal tumour of infancy and central nervous system high-grade neuroepithelial tumour with BCOR alteration all share similar internal tandem duplications in the polycomb-group really interesting new gene (RING) finger homolog ubiquitin-likefold discriminator domain of BCOR Translocations resulting in BCOR fusion with CCNB3, MAML3 and ZC3H7B have been identified in undifferentiated round cell sarcoma. Subsets of high-grade endometrial stromal sarcoma and ossifying fibromyxoid tumour which have a more aggressive clinical course have been shown to harbour ZC3H7B-BCOR fusions. BCOR immunohistochemistry is an established marker with diagnostic utility.

The c-Myc/AKT1/TBX3 Axis Is Important to Target in the Treatment of Embryonal Rhabdomyosarcoma.

Rhabdomyosarcoma is a highly aggressive malignant cancer that arises from skeletal muscle progenitor cells and is the third most common solid tumour in children. Despite significant advances, rhabdomyosarcoma still presents a therapeutic challenge, and while targeted therapy has shown promise, there are limited options because the molecular drivers of rhabdomyosarcoma are poorly understood. We previously reported that the T-box transcription factor 3 (TBX3), which has been identified as a druggable target in many cancers, is overexpressed in rhabdomyosarcoma patient samples and cell lines. To identify new molecular therapeutic targets to treat rhabdomyosarcoma, this study investigates the potential oncogenic role(s) for TBX3 and the factors responsible for upregulating it in this cancer. To this end, rhabdomyosarcoma cell culture models in which TBX3 was either stably knocked down or overexpressed were established and the impact on key hallmarks of cancer were examined using growth curves, soft agar and scratch motility assays, as well as tumour-forming ability in nude mice. Our data show that TBX3 promotes substrate-dependent and -independent proliferation, migration and tumour formation. We further reveal that TBX3 is upregulated by c-Myc transcriptionally and AKT1 post-translationally. This study identifies c-Myc/AKT1/TBX3 as an important axis that could be targeted for the treatment of rhabdomyosarcoma.

The Karyopherin proteins, Crm1 and Karyopherin beta1, are overexpressed in cervical cancer and are critical for cancer cell survival and proliferation.

The Karyopherin proteins are involved in nucleo-cytoplasmic trafficking and are critical for protein and RNA subcellular localization. Recent studies suggest they are important in nuclear envelope component assembly, mitosis and replication. Since these are all critical cellular functions, alterations in the expression of the Karyopherins may have an impact on the biology of cancer cells. In this study, we examined the expression of the Karyopherins, Crm1, Karyopherin beta1 (Kpnbeta1) and Karyopherin alpha2 (Kpnalpha2), in cervical tissue and cell lines. The functional significance of these proteins to cancer cells was investigated using individual siRNAs to inhibit their expression. Microarrays, quantitative RT-PCR and immunofluorescence revealed significantly higher expression of Crm1, Kpnbeta1 and Kpnalpha2 in cervical cancer compared to normal tissue. Expression levels were similarly elevated in cervical cancer cell lines compared to normal cells, and in transformed epithelial and fibroblast cells. Inhibition of Crm1 and Kpnbeta1 in cancer cells significantly reduced cell proliferation, while Kpnalpha2 inhibition had no effect. Noncancer cells were unaffected by the inhibition of Crm1 and Kpnbeta1. The reduction in proliferation of cancer cells was associated with an increase in a subG1 population by cell cycle analysis and Caspase-3/7 assays revealed increased apoptosis. Crm1 and Kpnbeta1 siRNA-induced apoptosis was accompanied by an increase in the levels of growth inhibitory proteins, p53, p27, p21 and p18. Our results demonstrate that Crm1, Kpnbeta1 and Kpnalpha2 are overexpressed in cervical cancer and that inhibiting the expression of Crm1 and Kpnbeta1, not Kpnalpha2, induces cancer cell death, making Crm1 and Kpnbeta1 promising candidates as both biomarkers and potential anticancer therapeutic targets.

Recent and rapid emergence of W-Beijing strains of Mycobacterium tuberculosis in Cape Town, South Africa.

BACKGROUND: There is increasing evidence of a strain-related variation in the virulence in Mycobacterium tuberculosis that may afford a selective advantage to certain strains. The W-Beijing strain family is globally distributed, highly virulent in animal models, associated with human immunodeficiency virus infection and drug resistance, and may be an emerging strain family. Our goal was to determine whether W-Beijing strains are expanding in a region of South Africa where rates of tuberculosis are among the highest in the world. METHODS: We used spoligotyping and single nucleotide polymorphism analysis to genotype all strains of tuberculosis from children presenting to the major pediatric referral hospital in Cape Town, South Africa over a period of 4 years and strains present in 352 archived histological samples from over a 76-year period. RESULTS: The proportion of W-Beijing strains from children increased from 13% to 33% from 2000 to 2003 (P= .026). With regard to the histological samples, W-Beijing strains were absent in the samples from the period 1930-1965 and rare in the samples from the period 1966-1995 (2.8% of samples), but they were increasingly common in samples from the period 1996-2005 (20% of samples; P= .001). CONCLUSIONS: The rapid expansion of W-Beijing strains in a region with a very high background incidence of tuberculosis suggests that these strains have a significant selective advantage. The biological reasons for this observation remain unclear but warrant further study. The rapid spread of this virulent strain lineage is likely to present additional challenges for tuberculosis control.

Gene of the month: SDH.

Succinate dehydrogenase (SDH) is a heterotetrameric nuclear encoded mitochondrial protein complex which plays a role in the citric acid cycle and the electron transfer chain. Germline mutations in SDHA are associated with Leigh syndrome. Mutations in SDHB, SDHC and SDHD are found in an increasing number of neoplasms, most notably paragangliomas and wild-type gastrointestinal stromal tumours. SDH deficiency in these tumours has important prognostic implications, and also provides a novel target for molecular therapy. In this article, we outline the structure and function of SDH and provide a summary of its role in various diseases.