Browsing by Author "Sanderson, Micheline"

Now showing 1 - 4 of 4
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    A biobank to support HIV malignancy research for sub-Saharan Africa
    (Health & Medical Publishing Group, 2016) Schneider, Johann Wilhelm; Sanderson, Micheline; Geiger, Dieter; Nokta, Mostafa; Silver, Sylvia
    Sub-Saharan Africa has one of the highest incidences of infection with HIV globally, but more people in this region are living longer owing to increased access to antiretroviral therapy. However, along with increased care and treatment, this population is expected to have an increase in HIV-associated cancers, as is being seen in the USA and other developed countries. To support translational research in HIV-associated cancers, Stellenbosch University in Cape Town, South Africa, was funded to house the state-of-the-art AIDS and Cancer Specimen Resource Sub-Saharan Africa Regional Biorepository (SSA RBR) to proactively obtain, manage and process biospecimens and associated clinical data representing both AIDS-defining and non-AIDS-defining cancers for research. The SSA RBR furthermore functions as the biorepository for AIDS Malignancy Consortium sub-Saharan clinical trial activities in this region. Although the site had much experience with cryopreservation and storage of specimens, capacity building revolving around operations under International Society for Environmental and Biological Resources/National Cancer Institute best practices took place in such areas as custodianship v. ownership, data sharing and facilities management. The process from selection until launch took 14 months.
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    An Evaluation of High‑Risk HPV in Squamous Cell Carcinomas of the Lip in a South African Cohort
    (Springer Nature, 2024-05-06) Harbor, Sharon N.; Schneider, Johann W.; Solomons, Nadine; Sanderson, Micheline; Afrogheh, Amir H.
    Background To determine the prevalence of HR-HPV in a series of lip SCC from South African patients, using currently accepted HPV-testing methodologies and to define the clinical and histomorphologic features of HPV-associated lip SCC. Methods Fifty SCC of lip and 50 control cases were tested for HR-HPV using p16 and HR-HPV DNA PCR. p16-equivocal/positive and HPV DNA PCR-positive SCC were further evaluated for the expression of HPV-16 and HPV-18 mRNA transcripts using reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) to confirm transcriptionally active HPV. Results p16 was positive in 22% (n = 11) and equivocal in 4% (n = 2) of the SCC. One p16-positive case showed positivity for both HPV-16 DNA and HPV-16 E6/E7 mRNA transcripts (HPV prevalence rate of 2%). The HPV-positive case was non-keratinizing and occurred in an 80-year-old female. The two p16-equivocal cases were HR-HPV DNA positive and mRNA PCR negative. p16 was found to have a positive predictive value of 9%. Conclusion Findings from our cohort of lip SCC suggest that HR-HPV may have an insignificant role in the pathogenesis of SCC at this site. Due to its low ppv, p16 is insufficient to establish HR-HPV infection in SCC of the lip. The combination of p16 and DNA PCR appears to correlate with the presence of transcriptionally active virus. HPV E6/E7 mRNA detection is the gold standard for identifying HR-HPV. mRNA testing is not widely available in sub-Saharan Africa due to technical and financial constraints; however, the test appears to be of great value in p16-equivocal lip SCC.
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    The role of MKP-1 in the anti-proliferative effects of glucocorticoids in primary rat pre-osteoblasts
    (Public Library of Science, 2015) Sanderson, Micheline; Sadie-Van Gijsen, Hanel; Hough, Stephen; Ferris, William F.
    Glucocorticoid (GC)-induced osteoporosis has been attributed to a GC-induced suppression of pre-osteoblast proliferation. Our previous work identified a critical role for mitogen-activated protein kinase (MAPK) phosphatase-1 (MKP-1) in mediating the anti-proliferative effects of GCs in immortalized pre-osteoblasts, but we subsequently found that MKP-1 null mice were not protected against the pathological effects of GCs on bone. In order to reconcile this discrepancy, we have assessed the effects of GCs on proliferation, activation of the MAPK ERK1/2 and MKP-1 expression in primary adipose-derived stromal cells (ADSCs) and ADSC-derived pre-osteoblasts (ADSC-OBs). ADSCs were isolated by means of collagenase digestion from adipose tissue biopsies harvested from adult male Wistar rats. ADSC-OBs were prepared by treating ADSCs with osteoblast differentiation media for 7 days. The effects of increasing concentrations of the GC dexamethasone on basal and mitogen-stimulated cell proliferation were quantified by tritiated thymidine incorporation. ERK1/2 activity was measured by Western blotting, while MKP-1 expression was quantified on both RNA and protein levels, using semi-quantitative real-time PCR and Western blotting, respectively. GCs were strongly anti-proliferative in both naïve ADSCs and ADSC-OBs, but had very little effect on mitogen-induced ERK1/2 activation and did not upregulate MKP-1 protein expression. These findings suggest that the anti-proliferative effects of GCs in primary ADSCs and ADSC-OBs in vitro do not require the inhibition of ERK1/2 activation by MKP-1, which is consistent with our in vivo findings in MKP-1 null mice.
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    The role of phosphatase activity and expression in glucocorticoid modulation of preosteoblasts
    (Stellenbosch : University of Stellenbosch, 2011-12) Sanderson, Micheline; Ferris, W. F.; Moolman-Smook, J. C.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Medicine. Internal Medicine.
    ENGLISH ABSTRACT: The increase in the prescription and use of glucocorticoids (GCs) to treat various diseases and resulting decrease in bone density and development of osteoporosis is of growing concern. Glucocorticoid-induced osteoporosis (GCIO) is a relatively under-researched disease with the mechanism by which GCs affect bone metabolism not yet fully delineated. This holds especially true for the early events in bone development. The negative effects of GCs are predominantly seen in osteoblasts, the cells responsible for bone formation, in that GCs diminish both the numbers and function of osteoblastic cells. Osteoblast precursor cell proliferation is crucial to ensure the existence of a healthy pool of osteoblastic cells needed to form new bone after bone resorption by osteoclasts. Previously, it was shown that GCs reduce the proliferation of immortalised osteoblastic cell lines. In addition, early immortalised preosteoblasts were more sensitive to GCs than their mature counterparts. However, these cells have corrupted cell cycles; therefore, primitive primary mesenchymal stromal cells (MSCs) were used in this study to examine the effect of GCs on the mitogen-induced proliferation of early osteoblast precursor cells (naïve MSCs and preosteoblasts) using the synthetic GC, dexamethasone (Dex). Mitogenic conditions established for naïve rat mesenchymal stromal cells (rMSCs) indicated that mild (5% FBS) stimulation is sufficient to induce proliferation, whereas a higher FBS concentration (20% FBS) was mitogenic in primary preosteoblasts. It was also found that pharmacological doses of Dex drastically decreased the mitogen-induced proliferation of both naïve rat MSCs (rMSCs) and preosteoblasts. Mitogen-activated protein kinase (MAPK) signalling pathways, such as ERK1/2, govern cell proliferation. GCs have been shown to decrease the activity of ERK1/2, which is associated with decreased proliferation in osteoblastic cells. In the present study, western blot analysis showed that Dex reduced the proliferation-associated shoulder of the ERK1/2 activity profile in both naïve rMSCs and preosteoblasts. Moreover, the ERK1/2 signalling pathway was shown to be essential for mitogen-stimulated growth of naïve rMSCs and preosteoblasts as the MEK1/2 inhibitor, U0126, inhibited mitogen-induced proliferation. Using western blot analysis, it was shown that, after mitogen administration, ERK1/2 activity exhibited a typical proliferation profile, which was blocked by U0126. Protein tyrosine phosphatases (PTPs) dephosphorylate and inactivate ERK1/2. Utilising sodium vanadate, an inhibitor of PTPs, in vitro phosphatase assays revealed that PTP activity was the predominant phosphatase activity present in naïve rMSCs and preosteoblast lysates after concomitant mitogen and Dex stimulation. The mRNA of the dual specificity phosphatase, MKP-1, was rapidly (within 30 minutes) upregulated after mitogen and Dex administration in both naïve rMSCs and preosteoblasts. However, the protein expression pattern of MKP-1 did not correspond to the mRNA induction, suggesting that the MKP-1 protein could be subjected to rapid degradation. These findings suggest that MKP-1 could possibly be involved in the GC regulation of mitogen-induced proliferation of early osteoblast precursor cells, but closer investigation is needed to fully elucidate this role. In addition, the involvement of other PTPs should not be excluded and warrants further investigation. During the course of the present study, it was found that strong mitogenic stimulation with 20% FBS led to oncogene-induced senescence (OIS). Flow cytometry analysis revealed the presence of two populations in naïve rMSCs preparations and DNA content analysis was consistent with that of cells undergoing OIS. These results indicated that the more primitive osteoblast precursor cells (naïve rMSCs) are more responsive to mitogens than their mature counterparts (preosteoblasts). In addition, it was found that the magnitude of ERK1/2 activation was increased in naïve rMSC after strong mitogenic stimulation, indicating that naïve rMSCs are still highly sensitive to stimulation with strong mitogens. In summary, these findings show that Dex decreased the proliferation of naïve rMSCs and preosteoblasts concomitantly with a decrease in ERK1/2 activity. In addition, Dex upregulated MKP-1 mRNA, but the same effect was not seen on the MKP-1 protein levels. Therefore, this suggests that PTP/s other than MKP-1 could be responsible for the inactivation of ERK1/2 by Dex, leading to decreased proliferation in naïve rMSCs and preosteoblasts. Further identification of PTPs that regulate osteoblast precursor cell numbers and function could lead to the elucidation of the mechanism through which GCs act to negatively influence bone density. This will improve our insights into the pathogenesis of GCIO and aid in the identification of therapeutic targets which can be exploited to develop new agents to treat osteoporosis.