Molecular characterization of Patched‐associated rhabdomyosarcoma

Abstract

Mutations in the human homologue of Drosophila Patched1 (PTCH1) have been found in several common tumours including basal cell carcinoma, medulloblastoma, and rhabdomyosarcoma (RMS). Medulloblastoma and RMS are also present in the murine model for Ptch1 deficiency. Tumours in heterozygous Ptch1(neo67/+) mice consistently exhibit elevated transcript levels of the proto-oncogene Gli1, of Ptch1 itself, and of the insulin-like growth factor 2 (Igf2). The present study has investigated additional molecular changes in RMSs of Ptch1 mutant mice by means of microarray analysis and protein expression analysis. The data show activation of the cell survival-promoting Akt/protein kinase B (Pkb). Furthermore, RMSs express increased levels of the anti-apoptotic protein Bcl-2 and of genes and proteins known to inhibit cell proliferation, including Gadd45a and p27kip1. Taken together, the data suggest that the formation of RMSs in Ptch1 mutants is associated with the ability of tumour cells to resist apoptosis.

The hedgehog regulated oncogenes Gli1 and Gli2 block myoblast differentiation by inhibiting MyoD-mediated transcriptional activation

“…Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed that Gli1 message was expressed at higher levels than Gli2 in primary tumor tissue (Supplementary Figure 1). This is consistent with previous characterizations of elevated Hh pathway activity and Gli1 expression in Ptch1 þ /À rhabdomyosarcomas (Hahn et al, 1998;Kappler et al, 2003).…”

Profiling the molecular difference between Patched- and p53-dependent rhabdomyosarcoma

“…Third, the relative abundance of genes such as Igf2, Foxf1, Gadd45a and Cav3 in RMS of heterozygous Ptch1 neo67/ þ mice in comparison to tumors of p53 þ /À mice is consistent with their involvement in Hedgehog/ Patched signaling (Hahn et al, 2000;Karpen et al, 2001;Kappler et al, 2003Kappler et al, , 2004. It has previously been described that Igf2 is highly expressed in RMS of heterozygous Ptch1 neo67/ þ mice, and that it is indispensable for tumor formation (Hahn et al, 2000).…”

“…Next, we stained for desmin, a widely used marker for RMS (Coindre, 2003), and found strong expression in all tumors examined, with desminpositive cells more prevalent in p53-dependent RMS. In addition, we stained for the antiapoptotic protein Bcl-2, which has recently been shown to be strongly expressed in 36% of human RMS, as well as in all cases of murine Ptch1-associated RMS (Boman et al, 1997;Kappler et al, 2003). We found high levels of Bcl-2 protein in RMS from both Ptch1 neo67/ þ and p53 þ /À mice.…”

“…We also ruled out severe alterations of p53 signaling in Ptch1-associated and of Hedgehog/Patched signaling in p53-associated tumors. However, some feature are shared by both tumor subtypes, notably expression of markers for RMS such as desmin and Bcl-2 (Boman et al, 1997;Merlino and Helman, 1999;Kappler et al, 2003), and the pattern of distribution of tumors to the trunk and extremities. The subtypes differed from each other in several points.…”

“…The same set of genes was strongly expressed in SM tissue, but not in C2C12 cells. Another interesting cluster of genes sharing differentially expression between the two RMS subtypes contained genes associated with Hedgehog/ Patched signaling ( Figure 6, upper panel), namely Igf2 (Hahn et al, 2000), forkhead box gene Foxf1 (Kappler et al, 2003), the growth arrest and DNA-damageinducible gene Gadd45a (Kappler et al, 2004), and caveolin 3 (Cav3) (Karpen et al, 2001). These genes generally exhibited higher transcript levels in Ptch1-dependend RMS rather than in p53-dependend RMS or SM tissue and C2C12 cells.…”