Abstract
Rhabdomyosarcoma (RMS), is the most frequent soft tissue tumor in children that originates from disturbances in differentiation process. Mechanisms leading to the development of RMS are still poorly understood. Therefore, by analysis of two RMS RH30 cell line subclones, one subclone PAX7 negative, while the second one PAX7 positive, and comparison with other RMS cell lines we aimed at identifying new mechanisms crucial for RMS progression. RH30 subclones were characterized by the same STR profile, but different morphology, rate of proliferation, migration activity and chemotactic abilities in vitro, as well as differences in tumor morphology and growth in vivo. Our analysis indicated a different level of expression of adhesion molecules (e.g., from VLA and ICAM families), myogenic microRNAs, such as miR-206 and transcription factors, such as MYOD, MYOG, SIX1, and ID. Silencing of PAX7 transcription factor with siRNA confirmed the crucial role of PAX7 transcription factor in proliferation, differentiation and migration of RMS cells. To conclude, our results suggest that tumor cell lines with the same STR profile can produce subclones that differ in many features and indicate crucial roles of PAX7 and ID proteins in the development of RMS.
Highlights
Myogenesis and myogenic differentiation are processes of muscle formation that are regulated by a number of transcription factors [1]
Culturing under differentiating conditions in medium with 2% horse serum (HS) indicated a higher percentage of PAX7+ cells in the G0/G1 phase and lower in S phase than PAX7− cells (Figure 1D,E), what suggests that PAX7+ cells might be more sensitive to starving differentiating conditions that may induce cell cycle arrest
We demonstrated that two subclones of RH30 cell line from different sources with the same STR profile, but with or without PAX7 expression, differ in multiple features, such as: morphology, proliferation, migration, chemotaxis, and cell growth in vivo
Summary
Myogenesis and myogenic differentiation are processes of muscle formation that are regulated by a number of transcription factors [1]. Myogenesis involves signaling pathways consisting of myogenic regulatory factors (MRF, such as MYF5, MYOD, MYOG, and MRF4), paired-homeobox transcription factors (PAX3 and PAX7) and sine oculis– related homeobox (SIX1 and SIX4) [2]. Lineage specification is regulated mainly by SIX1/4 and PAX3/7 transcription factors, whereas MYF5 and MYOD commit cells to the myogenic program. Cells in which PAX7 expression remains unchanged recreate a pool of undifferentiated satellite cells [2]. Another family of factors involved in the intramuscular differentiation are inhibitors of DNA binding/differentiation (IDs), belonging to the family of bHLH type transcription factors. The ID1 and ID2 proteins were shown to interact strongly with MYOD and MYF5 and weakly with myogenin and MRF4, while ID3 interacts strongly with all MRFs [7]
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