Scotin expression and survival in breast cancer

e22006

Background: The Scotin gene (3p21.3) is directly trans-activated by p53 in response to ionising radiation and produces a 25kD trans-membrane protein located in the endoplasmic reticulum and nuclear membrane which induces a caspase- dependent apoptosis. This study examines the expression of scotin and scotin isoforms in breast cancer in relation to clinical and pathological parameters. Methods: Scotin was examined in 145 breast cancers by DNA sequencing, nested PCR for mRNA expression and using novel antibodies to scotin (pantropic), the C-terminal or N-terminal domain, and the scotin-5 isoform with western blotting and immunohistochemistry on a tissue microarray of breast cancers. Results: Scotin was mutated in 10% of cancers and mRNA expression lost in a further 10%. Moreover, Scotin-5 was expressed in 40% of cancers, while it was not detectable in normal breast epithelium. We established that Scotin-5 is anti-apoptotic and inhibits scotin-mediated apoptosis. Cytoplasmic staining of scotin on TMAs demonstrated that loss of scotin expression was associated with earlier relapse (Mantel-Cox log rank p<0.01) and poor survival (Mantel-Cox log rank p<0.002). Furthermore, loss of Scotin expression identified 50% of the WTp53 patients or 50% of the ER+ patients who also had a poor survival. Conclusions: Scotin may be used as an independent biomarker in breast cancer. Loss of Scotin function may account for a significant proportion of p53 malfunction even in the presence of wild type p53 in breast cancer and adds a further level of complexity to p53 directed therapy in breast cancer.

No significant financial relationships to disclose.

The clinical relevance of p53 isoforms modifying the effects of p53 mutation on survival from breast cancer

10505

Background: p53 is a key gene in the development of breast cancer and response to therapy. Nine splice variants of p53 in breast cancer have been identified, with full length p53, p53beta and p53gamma (both 46kD, C terminal truncated proteins) commonly expressed. This study examined the clinical relevance of splice variants in breast cancer. Methods: Tumors from 248 patients with primary breast cancer were examined for mutation with the Roche p53 mutation chip and p53 isoform expression detected by RT-PCR followed by nested PCR; full clinical and pathological data included median follow up of 6.4 years. Results: p53 mutation, identified in 65/248 (26%) cancers, was significantly associated by Chi square test with shorter survival (p=0.001), histological grade 3 (p<0.001) and estrogen receptor (ER) negative cancers (p<0.001), as expected. Expression of p53 beta or p53 gamma mRNA was associated with p53 mutation (p=0.002, Fisher's exact test). Intriguingly, the patient groups with a mutant p53 cancer but expressing p53 gamma or p53 beta or both isoforms had survival curves comparable to patients with cancer containing wild type p53. Similarly, p53 gamma or p53 beta was associated with ER negative cancers (Chi square; p<0.001), but the group of ER negative tumors expressing p53 gamma or p53 beta had improved survival similar to ER positive cancers. Patients with p53 mutant, p53 beta negative and ER negative cancers comprised half of those who died within 3 years of diagnosis. Conclusions: p53 beta or p53 gamma isoform expression in breast cancer is associated with better prognosis and may moderate disease behaviour even in mutant p53 and ER negative cancers. Manipulation of p53 isoforms in breast cancer may thus offer therapeutic potential.

No significant financial relationships to disclose.

Calcium overload increases oxidative stress in old rat gastrocnemius muscle

In order to challenge in vivo muscle Ca2+ homeostasis and analyze consequences on mitochondrial H2O2 release (MHR) and sarcopenia, we injected Ca2+ ionophore A23187 (200 microg/kg, ip) in adult and old rats and measured gastrocnemius mass and mitochondrial Ca2+ content (MCC) using radioactive Ca2+ 48 h after injection. In a second experiment performed in old rats, we measured isocitrate dehydrogenase (ICDH) activity as an index of MCC, MHR, mitochondrial respiration, citrate synthase, COX and antioxydant enzyme activities 24 h after a 150 microg/kg injection. In adult rats, muscle mass and MCC were unchanged by A23187. In old rats, MCC increased 24 h after injection as reflected by a significant increase in ICDH activity; measured MCC tended to increase at 48 h. MHR and Mn-SOD activity were significantly increased at 24 h, and GPX activity was reduced. Muscle mass was unchanged but was negatively correlated with MCC in control and treated old rats. In conclusion, in old rats, A23187 probably induced a mitochondrial Ca2+ overload responsible for the observed increase in MHR without leading to muscle atrophy on a short term basis.

Due to reverse electron transfer, mitochondrial H2O2 release increases with age in human vastus lateralis muscle although oxidative capacity is preserved

Age-related changes in mitochondrial H2O2 release (MHR) could be responsible for an increase in oxidative stress in skeletal muscle and participate in the development of sarcopenia. We compared MHR in vastus lateralis biopsies obtained from young (23.5+/-2.0 year, n=6) and elderly (67.3+/-1.5 year, n=6) healthy sedentary men. Isolated mitochondria were incubated in the presence of glutamate/malate/succinate, with or without rotenone. Muscle fat oxidative capacity, citrate synthase, complex II, complex III, and cytochrome c oxidase activities were also measured. In parallel, we analyzed in gastrocnemius of young male Wistar rats (n=6), the impact of lidocaine (local anesthetic used in humans) on mitochondrial respiration and MHR. In humans, muscle oxidative capacity was preserved with age but muscle MHR was markedly enhanced in elderly subjects compared to young adults (+175%, P<0.05). Rotenone abolished this increase, demonstrating that it was due to a free radical release during reverse electron transfer from complex II towards complex I. Lidocaine can interfere with MHR measurements (intra-muscular injection in rats) but it can be avoided by minimizing contact with muscle (small multiple subcutaneous injections in humans). Physiologic consequences of the observed increase in muscle MHR with aging remain to be determined.

A Quantum Chemical Conformational Analysis of the Ethylenediamine Molecule

The conformational analysis of the ethylenediamine molecule has been studied by the LCAO-EHMO calculation method. The results indicate that the most stable conformation of the molecule is the gauche form, in which the angle N—C—C—N is ca. 63.0° measured from the cis form. This is in agreement with experimental data and can explain the fact that the ethylenediamine in its chelate complexes is always in the gauche form. In addition, the present results indicate that the trans form is the next most stable conformation of ethylenediamine in agreement with experimental results on bridging ethylenediamine metal complexes.