The cholinergic basal forebrain in the ferret and its inputs to the auditory cortex

Cholinergic inputs to the auditory cortex can modulate sensory processing and regulate stimulus‐specific plasticity according to the behavioural state of the subject. In order to understand how acetylcholine achieves this, it is essential to elucidate the circuitry by which cholinergic inputs influence the cortex. In this study, we described the distribution of cholinergic neurons in the basal forebrain and their inputs to the auditory cortex of the ferret, a species used increasingly in studies of auditory learning and plasticity. Cholinergic neurons in the basal forebrain, visualized by choline acetyltransferase and p75 neurotrophin receptor immunocytochemistry, were distributed through the medial septum, diagonal band of Broca, and nucleus basalis magnocellularis. Epipial tracer deposits and injections of the immunotoxin ME20.4‐SAP (monoclonal antibody specific for the p75 neurotrophin receptor conjugated to saporin) in the auditory cortex showed that cholinergic inputs originate almost exclusively in the ipsilateral nucleus basalis. Moreover, tracer injections in the nucleus basalis revealed a pattern of labelled fibres and terminal fields that resembled acetylcholinesterase fibre staining in the auditory cortex, with the heaviest labelling in layers II/III and in the infragranular layers. Labelled fibres with small en‐passant varicosities and simple terminal swellings were observed throughout all auditory cortical regions. The widespread distribution of cholinergic inputs from the nucleus basalis to both primary and higher level areas of the auditory cortex suggests that acetylcholine is likely to be involved in modulating many aspects of auditory processing.     

Other transgenic mutation assays: Tissue specificity of spontaneous point mutations in λsupF transgenic mice

Transgenic mice carrying multiple copies of a recoverable λ phage shuttle vector carrying the supF mutation reporter gene (λsupF) were constructed for the purpose of studying mutagenesis in a whole animal. Spontaneous mutations in rescued supF target genes from mouse liver and skin were analyzed. The mutation frequency was similar in both tissues (in the range of 2 × 10⁻⁵), but the spectrum of point mutations was distinct, with transitions common in the skin and transversions more prominent in the liver (P = 0.01). These results may help to elucidate pathways of endogenous mutagenesis in vivo, and they illustrate potentially important tissue-specific differences in genetic instability. © 1996 Wiley-Liss, Inc.     

Loss of glucose 6-phosphate dehydrogenase function increases oxidative stress and glutaminolysis in metastasizing melanoma cells

The pentose phosphate pathway is a major source of NADPH for oxidative stress resistance in cancer cells but there is limited insight into its role in metastasis, when some cancer cells experience high levels of oxidative stress. To address this, we mutated the substrate binding site of glucose 6-phosphate dehydrogenase (G6PD), which catalyzes the first step of the pentose phosphate pathway, in patient-derived melanomas. G6PD mutant melanomas had significantly decreased G6PD enzymatic activity and depletion of intermediates in the oxidative pentose phosphate pathway. Reduced G6PD function had little effect on the formation of primary subcutaneous tumors, but when these tumors spontaneously metastasized, the frequency of circulating melanoma cells in the blood and metastatic disease burden were significantly reduced. G6PD mutant melanomas exhibited increased levels of reactive oxygen species, decreased NADPH levels, and depleted glutathione as compared to control melanomas. G6PD mutant melanomas compensated for this increase in oxidative stress by increasing malic enzyme activity and glutamine consumption. This generated a new metabolic vulnerability as G6PD mutant melanomas were more dependent upon glutaminase than control melanomas, both for oxidative stress management and anaplerosis. The oxidative pentose phosphate pathway, malic enzyme, and glutaminolysis thus confer layered protection against oxidative stress during metastasis.

The pentose phosphate pathway is an important source of NADPH for oxidative stress resistance (1–5). The oxidative branch of the pentose phosphate pathway contains two enzymes that generate NADPH from NADP⁺, glucose 6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (PGD) (SI Appendix, Fig. S1). NADPH is an important source of reducing equivalents for oxidative stress resistance because it is used by cells to convert oxidized glutathione (GSSG) to glutathione (GSH), an abundant redox buffer. Complete deficiency for G6PD is embryonic-lethal in mice (2, 6, 7) but hypomorphic G6PD mutations are common in certain human populations, perhaps because they protect against malaria (8, 9). These partial loss-of-function G6PD mutations are well tolerated in adults, though they sensitize red blood cells to hemolysis from oxidative stress under certain circumstances (10).Several studies have reported a lower incidence and mortality for certain cancers in people with hypomorphic mutations in G6PD (11–14), suggesting that cancer cells depend upon G6PD to manage oxidative stress. Cells experience high levels of oxidative stress during certain phases of cancer development and progression, including during metastasis (15–17). Antioxidant mechanisms thus promote the survival of cells during oncogenic transformation (18, 19) as well as during metastasis (15, 16). For example, relative to primary cutaneous tumors, metastasizing melanoma cells exhibit increased dependence upon the folate pathway (15), monocarboxylate transporter-1 (MCT1) (20), and glutathione peroxidase-4 (GPX4) (21), each of which directly or indirectly attenuate oxidative stress. By better understanding the mechanisms that confer oxidative stress resistance in cancer cells, it may be possible to develop pro-oxidant therapies that inhibit cancer progression by exacerbating the oxidative stress experienced by cancer cells.G6PD (22) or PGD deficiency (23–25) reduce the growth of some cancers, including melanoma, but G6PD deficiency has little effect on primary tumor formation by K-Ras–driven epithelial cancers (26). This is at least partly because loss of G6PD in these cancers leads to compensatory increases in the function of other NADPH-generating enzymes, including malic enzyme and isocitrate dehydrogenase (1, 27). Nonetheless, pentose phosphate pathway function may increase during metastasis (20, 28–30) and higher G6PD expression is associated with worse outcomes in several cancers (31–33), raising the question of whether metastasizing cells are particularly dependent upon G6PD. G6PD is not essential for metastasis in a breast cancer cell line but it reduces their capacity to form metastatic tumors (26).Melanoma cells show little evidence of oxidative stress in established primary tumors but exhibit increased levels of reactive oxygen species (ROS) and dependence upon antioxidant mechanisms during metastasis (15, 20, 21). To test if these cells are more dependent upon the pentose phosphate pathway during metastasis, we generated three G6PD mutant melanomas, including two patient-derived xenografts and one human melanoma cell line. Reduced G6PD function had little effect on the formation or growth of primary subcutaneous tumors but significantly increased ROS levels and reduced spontaneous metastasis. G6PD mutant melanomas compensated by increasing malic enzyme activity and glutamine consumption, both to increase oxidative stress resistance and to replenish tricarboxylic acid (TCA) cycle intermediates through anaplerosis. Melanoma cells thus have redundant layers of protection against oxidative stress during metastasis, including the abilities to alter fuel consumption and antioxidant pathway utilization.     

Installing oncofertility programs for breast cancer in limited versus optimum resource settings: Empirical data from 39 surveyed centers in Repro-Can-OPEN Study Part I & II

PurposeAs a further step to elucidate the actual diverse spectrum of oncofertility practices for breast cancer around the globe, we present and discuss the comparisons of oncofertility practices for breast cancer in limited versus optimum resource settings based on data collected in the Repro-Can-OPEN Study Part I & II.MethodsWe surveyed 39 oncofertility centers including 14 in limited resource settings from Africa, Asia & Latin America (Repro-Can-OPEN Study Part I), and 25 in optimum resource settings from the United States, Europe, Australia and Japan (Repro-Can-OPEN Study Part II). Survey questions covered the availability of fertility preservation and restoration options offered to young female patients with breast cancer as well as the degree of utilization.ResultsIn the Repro-Can-OPEN Study Part I & II, responses for breast cancer and calculated oncofertility scores showed the following characteristics: (1) higher oncofertility scores in optimum resource settings than in limited resource settings especially for established options, (2) frequent utilization of egg freezing, embryo freezing, ovarian tissue freezing, GnRH analogs, and fractionation of chemo- and radiotherapy, (3) promising utilization of oocyte in vitro maturation (IVM), (4) rare utilization of neoadjuvant cytoprotective pharmacotherapy, artificial ovary, and stem cells reproductive technology as they are still in preclinical or early clinical research settings, (5) recognition that technical and ethical concerns should be considered when offering advanced and innovative oncofertility options.ConclusionsWe presented a plausible oncofertility best practice model to guide oncofertility teams in optimizing care for breast cancer patients in various resource settings.     

Fecal biomarkers in inflammatory bowel disease

Over the last two decades, knowledge on fecal biomarkers has substantially increased. Nowadays, these non‐invasive markers of inflammation have significant clinical utility in the management of inflammatory bowel disease. Their use informs the decision to perform endoscopy before diagnosis is made right through to influencing therapeutic choices and the need for interval endoscopic assessment. In this review, the roles of two S100 proteins, calprotectin, and S100A12 are described along with that of lactoferrin, in the context of inflammatory bowel disease.