SMAC-expression in denervated human skeletal muscle as a potential inhibitor of coexpressed inhibitor-of-apoptosis proteins.

In multinucleated skeletal muscle fibers, apoptotic muscle fiber loss is mediated by a consecutive disassembly of single fiber segments. During this period of time, proapoptotic and antiapoptotic factors compete for promotion or inhibition of apoptotic fiber degradation. In 16 patients with a neurogenic muscular atrophy, we studied the immunohistochemical expression of the inhibitor-of-apoptosis proteins (IAP) survivin, cIAP1, and XIAP and also of second mitochondria-derived activator of caspase (SMAC), which is released during apoptosis and binds to IAPs to prevent them from inhibiting caspases. Although normal control muscle fibers show no expression of SMAC and IAPs, there was a distinct sarcoplasmic expression of SMAC (12.0%+/-3.5%), survivin (10.2%+/-4.0%), cIAP1 (9.0%+/-3.1%), and XIAP (11.0%+/-4.6%) in varying numbers of muscle fibers in neurogenic muscular atrophy. Coexpression of SMAC and IAPs varied. Some denervated muscle fibers displayed up-regulation of either SMAC or IAPs. Other groups of atrophic muscle fibers showed coexpression of SMAC and IAPs. All factors were exclusively up-regulated in atrophic muscle fibers. These findings indicate that IAPs may inhibit apoptotic degradation of denervated muscle fibers. However, IAPs are finally insufficient to counterbalance and prevent muscle fiber apoptosis, as up-regulated expression of SMAC can antagonize this antiapoptotic potential and promote apoptotic muscle fiber disassembly and loss. The interplay between IAPs and SMAC may represent a threshold for muscle fiber-degrading caspase activities. If this bears a therapeutic potential in the prevention of loss of denervated muscle fibers, it remains highly speculative.

Reliability of human epidermal growth factor receptor 2 immunohistochemistry in breast core needle biopsies.

PURPOSE: Core needle biopsies (CNBs) are widely used to determine human epidermal growth factor receptor 2 (HER2) status in breast cancer. Recent publications reported up to 20% false-positive results on CNBs if immunohistochemistry (IHC) is compared with fluorescent in situ hybridization (FISH). To clarify, if confirmation of IHC positivity by FISH is generally required, we analyzed the reliability of IHC positivity on CNBs versus surgical specimens in a multi-institutional study. PATIENTS AND METHODS: Five pathologic laboratories contributed to this study by performing IHC on 500 CNBs and the corresponding surgical specimens overall. If IHC revealed score 2+ or 3+, HER2 status was confirmed by FISH in a central laboratory. We compared evaluation according to US Food and Drug Administration-approved scoring criteria and recently published American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines. RESULTS: CNBs scored 3+ revealed five false-positive results if scoring followed the US Food and Drug Administration criteria (five of 40; 12.5%) and two false-positives in terms of the ASCO-CAP criteria (two of 33; 6.1%). IHC was false negative in one CNB only. By contrast, IHC on surgical specimens revealed five false-negative results, but only one false-positive result (one of 35; 2.9%) if scored following US Food and Drug Administration-approved criteria. With the aid of the ASCO-CAP criteria, false-positive IHC results were obtained in only one of the five participating institutions. CONCLUSION: IHC 3+ scores on CNBs proved to be reliable in four of the five participating institutions if scoring followed the ASCO-CAP criteria. Therefore, accurate determination of HER2 status in breast cancer is possible on CNB using the common strategy to screen all cases by IHC and retest only 2+ scores by FISH. Prerequisites are quality assurance and the application of the new ASCO-CAP criteria.

Expression patterns of initiator and effector caspases in denervated human skeletal muscle.

There is evidence that apoptotic cell death contributes to the loss of denervated muscle fibers. In 17 patients with neurogenic muscular atrophy, we studied the expression of the apoptosis mediators APAF-1/caspase-9 and degrading caspases-2, -3, and -7 by immunohistochemical and western blot analyses. Muscle with neurogenic atrophy showed distinct upregulation of caspase-9 and -7 and no expression for APAF-1 (apoptosis protease-activating factor-1) and caspase-2 and -3. Expression of caspase-7 was restricted to atrophic fibers, but caspase-9 was also found in normal-sized muscle fibers where its expression was often confined to single fiber segments. These findings indicate that upregulated expression of caspase-9 can initiate the proteolytic cascade involving the downstream executioner caspase-7, which mediates degradation of denervated muscle fibers. However, apoptotic events may be restricted to single muscle-fiber segments, where apoptotic cell degradation contributes to the long-term process of atrophy. Pharmacological inhibition of caspases may be a therapeutic strategy in diminishing muscle atrophy.