Induction of terminal differentiation by constitutive activation of p38 MAP kinase in human rhabdomyosarcoma cells

Abstract

MyoD inhibits cell proliferation and promotes muscle differentiation. A paradoxical feature of rhabdomyosarcoma (RMS), a tumor arising from muscle precursors, is the block of the differentiation program and the deregulated proliferation despite MyoD expression. A deficiency in RMS of a factor required for MyoD activity has been implicated by previous studies. We report here that p38 MAP kinase (MAPK) activation, which is essential for muscle differentiation, is deficient in RMS cells. Enforced induction of p38 MAPK by an activated MAPK kinase 6 (MKK6EE) restored MyoD function and enhanced MEF2 activity in RMS deficient for p38 MAPK activation, leading to growth arrest and terminal differentiation. Stress and cytokines could activate the p38 MAPK in RMS cells, however, these stimuli did not promote differentiation, possibly because they activated p38 MAPK only transiently and they also activated JNK, which could antagonize differentiation. Thus, the selective and sustained p38 MAPK activation, which is distinct from the stress-activated response, is required for differentiation and can be disrupted in human tumors.

Anti‑oncogenic and pro‑myogenic action of the MKK6/p38/AKT axis induced by targeting MEK/ERK in embryonal rhabdomyosarcoma

“…It has previously been reported that the enforced induction of MKK6/p38 pathways restores the myogenic differentiation of ERMS cell lines ( 10 ). The present study demonstrates for the first time, to the best of our knowledge, that extracellular signals, such as those induced by the MEK/ERK inhibitor within the pathological myogenesis of ERMS, restore the activation of endogenous MKK6/p38.…”

“…no. 14670; Addgene, Inc.), expressing dominant negative and constitutively active MKK3 isoforms, respectively; the MKK6-EE (caMKK6-EE) constitutively active form of MKK6 was a gift from Professor Puri Pier Lorenzo (Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA) ( 10 ). Plasmids expressing shRNA specific for p38α knockdown and puromycin resistance for transfected cell selection were obtained from OriGene Technologies, Inc. shRNAs were cloned in the pRS plasmid under the U6 promoter, with puromycin as selectable marker and ampicillin as bacterial resistance.…”

“…Taking into account the data available on the promyogenic role of MKK6 (10), the present study aimed to investigate the possible differential roles played by MKK3 and MKK6 in the ERMS reversal of the transformed phenotype. MKK3 and MKK6 expression levels in ERMS primary biopsies compared to NSM were obtained by interrogating three different public transcriptomic datasets deposited on the R2-Genomics Analysis and Visualization Platform (http://r2.amc.nl).…”

“…The abnormal expression of Ras leads to the upregulation of these pathways and, consequently, to tumorigenesis ( 9 ). The constitutive activation of ERKs, which results from Ras mutations in RMS cells, leads to the reduced capacity of myodifferentiation due to the inhibition of p38 signalling ( 10 ), which is known to regulate the expression of specific skeletal muscle genes ( 11 , 12 ). Indeed, MEK/ERK inhibition in RD cells has been shown to induce the p38-dependent rescue of the myogenic program that is also related to a marked c-Myc downregulation ( 13 , 14 ).…”

Curcumin Induces Apoptosis of Chemoresistant Lung Cancer Cells via ROS-Regulated p38 MAPK Phosphorylation

“…The canonical activation pathway of p38 MAPK phosphorylation at the Thr180 and Tyr182 residues is essential to activate its kinase activity to either prevent or induce apoptosis [ 41 ]. The intensity of p38 MAPK activation has been linked with its pro-death or pro-survival role, whereby potent p38 MAPK activation is associated with senescence [ 42 ] and terminal cell differentiation [ 43 ]. On the other hand, normal p38 activation has a cell survival effect [ 44 ].…”