Inheritance of resistance to fenthion in Culex pipiens fatigans Wied

The insecticide fenthion, which shows great promise for controlling the filariasis vector Culex pipiens fatigans, has been found in the laboratory to induce a certain amount of resistance. As the biochemical nature of fenthion resistance was known to be due to an increase in a particular esterase activity, the inheritance of the character was investigated in the present study. It was found to be mainly due to a single slightly recessive gene associated with linkage-group 2, and the increase in detoxifying esterase activity showed a similar inheritance.     

Absence of FGFR3 mutations in urinary bladder tumours of rats and mice treated with N-butyl-N-(-4-hydroxybutyl)nitrosamine

Frequent activating mutations of FGFR3 (fibroblast growth factor receptor 3) are found in human urothelial cell carcinomas, particularly in superficial papillary tumours (in 74%-84% of pTaG1-G2), but not in carcinomas in situ (CIS) and at a low rate in invasive tumours (in 16%-21% of pT1-4). In mice and rats, BBN (N-butyl-N-(4-hydroxybutyl)nitrosamine) specifically induces bladder tumours. In rats, superficial papillary tumours are mostly observed. In mice, tumour progression follows the CIS pathway: CIS are first observed, followed by tumours that invade surrounding muscle. Therefore, we looked for FGFR3 mutations in these two animal models of bladder cancer. Only the FGFR3b isoform is expressed in human urothelium and derived tumours. We identified the FGFR3b isoform in rats for the first time and showed that this is the main isoform expressed in the bladder urothelium and derived carcinomas in mice and rats, as in humans. SSCP and sequence analysis of FGFR3b showed sequence changes (polymorphisms or silent mutations) in four BBN-induced rat and mouse bladder tumours. The absence of activating mutations of FGFR3 in the mouse model was in agreement with the fact that mouse BBN-induced bladder tumour progression mimics the CIS pathway. The absence of FGFR3 mutations in the rat bladder tumours suggests that, at least at the genetic level, rat superficial papillary tumours differ from their human counterparts.     

Identification of novel VHL target genes and relationship to hypoxic response pathways

Upregulation of hypoxia-inducible factors HIF-1 and HIF-2 is frequent in human cancers and may result from tissue hypoxia or genetic mechanisms, in particular the inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene (TSG). Tumours with VHL inactivation are highly vascular, but it is unclear to what extent HIF-dependent and HIF-independent mechanisms account for pVHL tumour suppressor activity. As the identification of novel pVHL targets might provide insights into pVHL tumour suppressor activity, we performed gene expression microarray analysis in VHL-wild-type and VHL-null renal cell carcinoma (RCC) cell lines. We identified 30 differentially regulated pVHL targets (26 of which were 'novel') and the results of microarray analysis were confirmed in all 11 novel targets further analysed by real-time RT-PCR or Western blotting. Furthermore, nine of 11 targets were dysregulated in the majority of a series of primary clear cell RCC with VHL inactivation. Three of the nine targets had been identified previously as candidate TSGs (DOC-2/DAB2, CDKN1C and SPARC) and all were upregulated by wild-type pVHL. The significance for pVHL function of two further genes upregulated by wild-type pVHL was initially unclear, but re-expression of GNG4 (G protein gamma-4 subunit/guanine nucleotide-binding protein-4) and MLC2 (myosin light chain) in a RCC cell line suppressed tumour cell growth. pVHL regulation of CDKN1C, SPARC and GNG4 was not mimicked by hypoxia, whereas for six of 11 novel targets analysed (including DOC-2/DAB2 and MLC2) the effects of pVHL inactivation and hypoxia were similar. For GPR56 there was evidence of a tissue-specific hypoxia response. Such a phenomenon might, in part, explain organ-specific tumorigenesis in VHL disease. These provide insights into mechanisms of pVHL tumour suppressor function and identify novel hypoxia-responsive targets that might be implicated in tumorigenesis in both VHL disease and in other cancers with HIF upregulation.     

PK11195 potently sensitizes to apoptosis induction independently from the peripheral benzodiazepin receptor

1-(2-Chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide (PK11195) is a prototypic ligand of the peripheral benzodiazepine receptor (PBR), a mitochondrial outer membrane protein. PK11195 can be used to chemosensitize tumor cells to a variety of chemotherapeutic agents, both in vitro and in vivo. PK11195 has been suggested to exert this effect via inhibition of the multiple drug resistance (MDR) pump and by direct mitochondrial effects which could be mediated by the PBR. Here, we established a model system in which PK11195 and another PBR ligand, 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one (Ro5-4864), sensitize to nutrient depletion-induced cell death. In this MDR-independent model, PK11195 and Ro5-4864 are fully active even when the PBR is knocked down by small interfering RNA. Cells that lack PBR possess low-affinity binding sites for PK11195 and Ro5-4864. The starvation-sensitizing effects of PK11195 are not due to a modulation of the adaptive response of starved cells, namely autophagy and NF-kappaB activation. Rather, it appears that the combination of PK11195 with autophagy or NF-kappaB inhibitors has a potent synergistic death-inducing effect. Starved cells treated with PK11195 exhibit characteristics of apoptosis, including loss of the mitochondrial transmembrane potential, mitochondrial cytochrome c release, caspase activation and chromatin condensation. Accordingly, stabilization of mitochondria by overexpression of Bcl-2 or expression of the viral mitochondrial inhibitor (vMIA) from cytomegalovirus inhibits cell death induced by PK11195 plus starvation. Thus, PK11195 potently sensitizes to apoptosis via a pathway that involves mitochondria, yet does not involve the PBR.     

Crypt-restricted loss and decreased protein expression of cytochrome C oxidase subunit I as potential hypothesis-driven biomarkers of colon cancer risk.

There is an increasing demand for the development of intermediate biomarkers to assess colon cancer risk. We previously determined that a live cell bioassay, which assesses apoptosis resistance in the nonneoplastic colonic mucosa, detects approximately 50% of patients with colon cancer. A hypothesis-driven biomarker that reflects apoptosis resistance in routine formalin-fixed, paraffin-embedded tissue would be easier to use. Cytochrome c oxidase is a critical enzyme that controls mitochondrial respiration and is central to apoptosis. We did an immunohistochemical study of cytochrome c oxidase subunit I expression in 46 colonic mucosal samples from 16 patients who had undergone a colonic resection. These included five patients without evidence of colonic neoplasia (three normal and two diverticulitis), three patients with tubulovillous adenomas, and eight patients with colonic adenocarcinomas. Analysis of aberrancies in expression of cytochrome c oxidase subunit I showed that, compared with nonneoplasia, the patients with neoplasia had a higher mean incidence of crypts having decreased expression (1.7 versus 22.8, P = 0.03) and a higher mean incidence having crypt-restricted loss (0.6 versus 3.2, P = 0.06). The percentage with segmented loss was low and was similar in the two groups. Combining these results, the mean % normal (i.e., with none of the three types of abnormality) was 96.7 in nonneoplasia versus only 73.2 in patients with neoplasia (P = 0.02). It should be noted that a defect in cytochrome c oxidase subunit I immunostaining was not detected in all biopsy samples from each patient for whom some abnormality was found, indicating a "patchiness" in the cytochrome c oxidase subunit I field defect. As a result of this "patchiness," the increased variability in the incidence of crypt-restricted loss of cytochrome c oxidase subunit I expression was a statistically significant feature of the neoplasia group. Crypt-restricted loss of cytochrome c oxidase subunit I has not been previously reported in colonic mucosa and is presumably the result of a crypt-restricted stem cell mutation. Decreased cytochrome c oxidase subunit I expression also significantly correlated with apoptosis resistance, a factor known to contribute to carcinogenesis. The results suggest, however, that aberrant cytochrome c oxidase subunit I expression may be a better biomarker than loss of apoptosis competence for increased colon cancer risk.     

The relationship between available support, unmet needs and caregiver burden in patients with advanced cancer and their carers

Caregiver burden is an increasing problem with patients surviving longer and more care tasks falling to informal caregivers. While research has identified patient and caregiver variables associated with caregiver burden, less research has focused on aspects of the care environment. The present study investigated the available support and unmet needs of 57 patients with advanced cancer, 45 of their carers and 40 of their health professionals. Carers and patients consistently identified higher levels of available support for the patient than health care professionals, with carers identifying higher levels of support than patients. Carers also identified more patient unmet needs than health care professionals, who in turn identified more than patients. Surprisingly, available support did not increase over 6 months and there was a tendency for unmet needs to decrease over time. Low available support, high unmet needs and a larger discrepancy between carer and patients' reports of patients' unmet need predicted negative aspects of caregiver burden. These results suggest that health care professionals underestimate available support to patients and both patients and health care professionals underestimate patients' unmet needs in comparison to carers. Carers' reports of patients' unmet needs are important to consider as they were associated with high levels of caregiver burden, including poorer caregiver health. Health care professionals should encourage opportunities for carers to discuss their views of the ongoing needs of patients with advanced cancer.