calpain and Rhabdomyosarcoma--Alveolar

Rhabdomyosarcoma (RMS) are soft-tissue sarcoma commonly encountered in childhood. RMS cells can acquire invasive behavior and form metastases. The metastatic dissemination implicates many proteases among which are mu-calpain and m-calpain. Study of calpain expression and activity underline the deregulation of calpain activity in RMS. Analysis of kinetic characteristics of RMS cells, compared to human myoblasts LHCN-M2 cells, shows an important migration velocity in RMS cells. One of the major results of this study is the positive linear correlation between calpain activity and migration velocity presenting calpains as a marker of tumor aggressiveness. The RMS cytoskeleton is disorganized. Specifying the role of mu- and m-calpain using antisense oligonucleotides led to show that both calpains up-regulate alpha- and beta-actin in ARMS cells. Moreover, the invasive behavior of these cells is higher than that of LHCN-M2 cells. However, it is similar to that of non-treated LHCN-M2 cells, when calpains are inhibited. In summary, calpains may be involved in the anarchic adhesion, migration and invasion of RMS. The direct relationship between calpain activity and migration velocities or invasive behavior indicates that calpains could be considered as markers of tumor aggressiveness and as potential targets for limiting development of RMS tumor as well as their metastatic behavior.

Topics: Actins; Blotting, Western; Calcium-Binding Proteins; Calpain; Cell Adhesion; Cell Movement; Cell Proliferation; Cells, Cultured; Cytoskeleton; Humans; Myoblasts; Neoplasm Invasiveness; Reverse Transcriptase Polymerase Chain Reaction; Rhabdomyosarcoma, Alveolar; RNA, Messenger

Peroxiredoxin IV (Prx IV), a member of the peroxiredoxin family, has been shown to be involved in cell protection against radiation. Peroxiredoxins are also overexpressed and involved in the progression of several tumours. Calpains have been shown to be over-activated in alveolar rhabdomyosarcoma (ARMS). The present study focused on the possible cross-regulations between Prx IV and calpains in ARMS cells. Prx IV abundance was quantified by Western blot analysis in ARMS cells and compared with non-malignant LHCN-M2 cells. Its abundance is quantified in ARMS cells treated or untreated with calpain inhibitors moreover its mRNA expression is also quantified by real-time RT-PCR in these cells. The study showed that Prx IV is overexpressed by five times in ARMS cells when compared to non-malignant myoblasts. Moreover, the inhibition of calpains using chemical inhibitors led to a decrease in Prx IV abundance (64.32 ± 8.25 and 76.79 ± 4.60 for the precursor and secretable forms, respectively, with calpain inhibitor III treatment). It is the first time that a Prx IV calpain-dependent up-regulation is revealed. In summary, calpains may be implied in the tumour phenotype of ARMS cells especially through Prx IV regulation and may, thus, represent a potential therapeutic target to stop progression of ARMS tumour.

Topics: Calpain; Cell Line; Cell Line, Tumor; Humans; Myoblasts; Peroxiredoxins; Rhabdomyosarcoma, Alveolar; RNA, Messenger; Up-Regulation