Inactivation of the transforming growth factor β type II receptor in human small cell lung cancer cell lines

Transforming growth factor β (TGF-β) exerts a growth inhibitory effect on many cell types through binding to two types of receptors, the type I and II receptors. Resistance to TGF-β due to lack of type II receptor (RII) has been described in some cancer types including small cell lung cancer (SCLC). The purpose of this study was to examine the cause of absent RII expression in SCLC cell lines. Northern blot analysis showed that RII RNA expression was very weak in 16 of 21 cell lines. To investigate if the absence of RII transcript was due to mutations, we screened the poly-A tract for mutations, but no mutations were detected. Additional screening for mutations of the RII gene revealed a GG to TT base substitution in one cell line, which did not express RII. This mutation generates a stop codon resulting in predicted synthesis of a truncated RII of 219 amino acids. The nature of the mutation, which has not previously been observed in RII, has been linked to exposure to benzo[a]-pyrene, a component of cigarette smoke. Since RII has been mapped to chromosome 3p22 and nearby loci are often hypermethylated in SCLC, it was examined whether the lack of RII expression was due to hypermethylation. Southern blot analysis of the RII promoter did not show altered methylation patterns. The restriction endonuclease pattern of the RII gene was altered in two SCLC cell lines when digested with Sma 1. However, treatment with 5-aza-2′-deoxycytidine did not induce expression of RII mRNA. Our results indicate that in SCLC lack of RII mRNA is not commonly due to mutations and inactivation of RII transcription was not due to hypermethylation of the RII promoter or gene. Thus, these data show that in most cases of the SCLC cell lines, the RII gene and promoter is intact in spite of absent RII expression. However, the nature of the mutation found could suggest that it was caused by cigarette smoking. © 1999 Cancer Research Campaig

Restoration of TGF-β signalling reduces tumorigenicity in human lung cancer cells

Members of the transforming growth factor-β (TGF-β) family regulate a wide range of biological processes including cell proliferation, migration, differentiation, apoptosis, and extracellular matrix deposition. Resistance to TGF-β-mediated tumour suppressor function in human lung cancer may occur through the loss of type II receptor (TβRII) expression. In this study, we investigated the expression pattern of TβRII in human lung cancer tissues by RT–PCR and Western blot analyses. We observed downregulation of TβRII in 30 out of 46 NSCLC samples (65%) by semiquantitative RT–PCR. Western blot analyses with tumour lysates showed reduced expression of TβRII in 77% cases. We also determined the effect of TβRII expression in lung adenocarcinoma cell line (VMRC-LCD) that is not responsive to TGF-β due to lack of TβRII expression. Stable expression of TβRII in these cells restored TGF-β-mediated effects including Smad2/3 and Smad4 complex formation, TGF-β-responsive reporter gene activation, inhibition of cell proliferation and increased apoptosis. Clones expressing TβRII showed reduced colony formation in soft-agarose assay and significantly reduced tumorigenicity in athymic nude mice. Therefore, these results suggest that reestablishment of TGF-β signalling in TβRII null cells by stable expression of TβRII can reverse malignant behaviour of cells and loss of TβRII expression may be involved in lung tumour progression

Smad phosphoisoform signaling specificity: the right place at the right time

Transforming growth factor (TGF)-β antagonizes mitogenic Ras signaling during epithelial regeneration, but TGF-β and Ras act synergistically in driving tumor progression. Insights into these apparently contradictory effects have come from recent detailed analyses of the TGF-β signaling process. Here, we summarize the different modes of TGF-β/Ras signaling in normal epithelium and neoplasms and show how perturbation of TGF-β signaling by Ras may contribute to a shift from tumor-suppressive to protumorigenic TGF-β activity during tumor progression. Smad proteins, which convey signals from TGF-β receptors to the nucleus, have intermediate linker regions between conserved Mad homology (MH) 1 and MH2 domains. TGF-β Type I receptor and Ras-associated kinases differentially phosphorylate Smad2 and Smad3 to create C-terminally (C), linker (L) or dually (L/C) phosphorylated (p) isoforms. In epithelial homeostasis, TGF-β-mediated pSmad3C signaling opposes proliferative responses induced by mitogenic signals. During carcinogenesis, activation of cytoplasmic Ras-associated kinases including mitogen-activated protein kinase confers a selective advantage on benign tumors by shifting Smad3 signaling from a tumor-suppressive pSmad3C to an oncogenic pSmad3L pathway, leading to carcinoma in situ. Finally, at the edges of advanced carcinomas invading adjacent tissues, nuclear Ras-associated kinases such as cyclin-dependent kinases, together with cytoplasmic kinases, alter TGF-β signals to more invasive and proliferative pSmad2L/C and pSmad3L/C signaling. Taken together, TGF-β signaling specificity arises from spatiotemporal dynamics of Smad phosphoisoforms. Based on these findings, we have reason to hope that pharmacologic inhibition of linker phosphorylation might suppress progression to human advanced carcinomas by switching from protumorigenic to tumor-suppressive TGF-β signaling

HER-2 overexpression differentially alters transforming growth factor-β responses in luminal versus mesenchymal human breast cancer cells

INTRODUCTION: Amplification of the HER-2 receptor tyrosine kinase has been implicated in the pathogenesis and aggressive behavior of approximately 25% of invasive human breast cancers. Clinical and experimental evidence suggest that aberrant HER-2 signaling contributes to tumor initiation and disease progression. Transforming growth factor beta (TGF-β) is the dominant factor opposing growth stimulatory factors and early oncogene activation in many tissues, including the mammary gland. Thus, to better understand the mechanisms by which HER-2 overexpression promotes the early stages of breast cancer, we directly assayed the cellular and molecular effects of TGF-β1 on breast cancer cells in the presence or absence of overexpressed HER-2. METHODS: Cell proliferation assays were used to determine the effect of TGF-β on the growth of breast cancer cells with normal or high level expression of HER-2. Affymetrix microarrays combined with Northern and western blot analysis were used to monitor the transcriptional responses to exogenous TGF-β1 in luminal and mesenchymal-like breast cancer cells. The activity of the core TGF-β signaling pathway was assessed using TGF-β1 binding assays, phospho-specific Smad antibodies, immunofluorescent staining of Smad and Smad DNA binding assays. RESULTS: We demonstrate that cells engineered to over-express HER-2 are resistant to the anti-proliferative effect of TGF-β1. HER-2 overexpression profoundly diminishes the transcriptional responses induced by TGF-β in the luminal MCF-7 breast cancer cell line and prevents target gene induction by a novel mechanism that does not involve the abrogation of Smad nuclear accumulation, DNA binding or changes in c-myc repression. Conversely, HER-2 overexpression in the context of the mesenchymal MDA-MB-231 breast cell line potentiated the TGF-β induced pro-invasive and pro-metastatic gene signature. CONCLUSION: HER-2 overexpression promotes the growth and malignancy of mammary epithelial cells, in part, by conferring resistance to the growth inhibitory effects of TGF-β. In contrast, HER-2 and TGF-β signaling pathways can cooperate to promote especially aggressive disease behavior in the context of a highly invasive breast tumor model

Prevalence and Predictors of Tuberculosis Coinfection among HIV-Seropositive Patients Attending the Aminu Kano Teaching Hospital, Northern Nigeria

Background: The HIV/AIDS epidemic has been accompanied by a severe epidemic of tuberculosis (TB), although the prevalence of coinfection is largely unknown, especially in developing countries, including Nigeria. The aim of this study was to determine the prevalence and predictors of TB coinfection among HIV-seropositive Nigerians. Methods: The case files of HIV/AIDS patients attending Aminu Kano Teaching Hospital, Nigeria from January to December 2006 were reviewed. Results: A total of 1320 HIV/AIDS patients had complete records and were reviewed, among which 138 (10.5%) were coinfected with TB (95% CI, 8.9% to 12.2%). Pulmonary TB was diagnosed in 103 (74.6%) patients, among whom only 18 (17.5%) were sputum-positive. Fifty (36.2%) coinfected patients had some type of extrapulmonary TB (EPTB); 15 had both pulmonary TB and EPTB. Among the 35 patients with EPTB only, 20 (57.1%) had abdominal TB, 5 (14.3%) had TB adenitis, 5 (14.3%) had spinal TB, 3 (8.6%) were being monitored for tuberculous meningitis, and 1 (2.9%) each had renal TB and tuberculous adrenalitis. The highest prevalence of TB, 13.7% (n = 28), was seen among patients aged 41–50 years. TB coinfection was significantly associated with marital status, WHO clinical stage, and CD4 count. Marital status (OR, 2.1; 95% CI, 1.28–3.59; P = 0.04), WHO clinical stage at presentation (4.81; 1.42–8.34; P = 0.001), and baseline CD4 count (2.71; 1.51–6.21; P = 0.02) remained significant predictors after adjustment for confounding. Conclusions: The moderately high prevalence of TB among HIV-seropositive patients underscores the urgent need for strategies that lead to rapid identification and treatment of coinfection with active or latent TB

Postoperative Spinal Orthoses: Types and Outcomes

INTRODUCTIONPostoperative bracing (POB) after spinal surgery is a common practice that has been used for many decades. In the past few years, the indications, types, and outcomes of POB have been heavily questioned after many studies revealed no consistent evidence to support or refute the use of spinal orthoses after surgery. SUMMARYCurrently, there are no indications of the type, duration, or indication for many spinal orthoses and few studies have assessed their efficacy. Although much of the literature lacks adequate comparisons of brace types or specific indications, POB is still widely used for various surgical procedures. This study evaluated the current evidence concerning POB of the cervical, thoracic, and lumbosacral spine

Top 50 most cited articles in revision total hip arthroplasty research

Bibliometric analysis is a useful tool for measuring the scholarly impact of a topic. To date, there is no such review analyzing the characteristics and trends of publications focused on revision total hip arthroplasty (rTHA). The purpose of this study is to use bibliometric analysis to comprehensively analyze the 50 most cited articles in rTHA research. This is a cross-sectional study that used the ISI Web of Knowledge database to identify articles published before September 2021. Articles were sorted in descending order by number of citations and those with a focus of rTHA were identified. Of these, the top 50 most cited articles were carried forward for evaluation. The 2000s (50%) and the 1990s (32%) had the greatest volume of contribution. 9 of the top 10 most cited articles were published in the 2000s. The highest impact article had 4702 citations. The level of evidence (LOE) published with the greatest frequency was LOE II (40%) followed by LOE III and LOE IV both recording 24%. The Journal of Bone and Joint Surgery-American Volume had the greatest productivity (46%) followed by The Journal of Bone and Joint Surgery-British Volume (18%). The United States was the country with the highest number of contributions to this list with 56% followed by England (12%), and Sweden and Canada both with 8%. The most impactful articles focusing on rTHA research were comprehensively and objectively analyzed. The most common article type was clinical outcomes (46%) followed by natural history/epidemiology (24%) and surgical technique (16%). While this topic is highly studied with significant level of evidence to support the studies, there is a lack of influential research regarding imaging and clinical guidelines. This analysis can be used by researchers to develop further discussions and build research questions

Orthopaedic Surgery Residency Application, and Selection Criteria Adaptations, in Times of COVID-19 A Survey Study

Amid the COVID-19 pandemic, medical education and residency application have faced unprecedented changes. This has forced residency directors to alter their selection criteria in the absence of away rotations and the implementation of nationwide virtual interviews. PURPOSE: The purpose of this study was to assess how residency directors have adapted their selection criteria in light of this unique application cycle and to look at the effect, and future, of the different changes. METHODS: A 16-question online survey was disseminated to 31 residency programs gathering data about new opportunities offered this cycle, changes to selection criteria, match outcomes, as well as the number of applicants to their program. RESULTS: Twenty-nine respondents completed the survey (94% response rate). There was a significant rise in the number of applications received by programs this cycle (p < 0.05). Programs have unanimously altered their selection processes. The biggest changes in selection criteria were putting more weight into communication from mentors, emails from the applicants, home applicant status, and virtual information session attendance. Some programs used additional application requirements beyond Electronic Residency Application Service, which were often uncompleted, and cut the number of eligible applications by up to 46%. Among the new opportunities offered this cycle, virtual information sessions and social media platforms seem to be the most commonly offered and are anticipated to grow. DISCUSSION AND CONCLUSION: Orthopaedic surgery residency continues to become more competitive with a significant rise in the number of applications during the COVID-19 pandemic. Amid this increasingly demanding virtual application cycle, a holistic application review was more challenging. More weight was put that cycle into communication from faculty mentors, emails from the applicants, home applicant status, and virtual information session attendance. Supplementary applications and virtual informative opportunities are likely to last and change the future of the orthopaedic surgery residency application process