The RAS isoforms are frequently mutated in many types of human cancers, including PAX3/PAX7 fusion-negative rhabdomyosarcoma. Pediatric RMS arises from skeletal muscle progenitor cells that have failed to differentiate normally. The role of mutant RAS in this differentiation blockade is incompletely understood. We demonstrate that oncogenic RAS, acting through the RAF-MEK [mitogen-activated protein kinase (MAPK) kinase]-ERK (extracellular signal-regulated kinase) MAPK effector pathway, inhibits myogenic differentiation in rhabdomyosarcoma by repressing the expression of the prodifferentiation myogenic transcription factor, MYOG. This repression is mediated by ERK2-dependent promoter-proximal stalling of RNA polymerase II at the locus. Small-molecule screening with a library of mechanistically defined inhibitors showed that RAS-driven RMS is vulnerable to MEK inhibition. MEK inhibition with trametinib leads to the loss of ERK2 at the promoter and releases the transcriptional stalling of expression. MYOG subsequently opens chromatin and establishes super-enhancers at genes required for late myogenic differentiation. Furthermore, trametinib, in combination with an inhibitor of IGF1R, potently decreases rhabdomyosarcoma cell viability and slows tumor growth in xenograft models. Therefore, this combination represents a potential therapeutic for RAS-mutated rhabdomyosarcoma.

Hyperbranched polymers (HBPs) are increasingly attracting the attention of scientists due to their unique physical and chemical 5 properties, as well as their potential applications in different fields. Many methods for the preparation of HBPs have hitherto been reported. This review focuses primarily on several novel synthesis methods for various HBPs. We present and discuss the advantages and disadvantages as well as recent progress relating to these synthesis methods, namely the slow monomer addition method, click chemistry, and the enzyme-catalyzed polymerization method. Besides, the applications of HBPs in analytical chemistry fields such as sample pretreatment and immunosensors are also briefly summarized. 10

It can be concluded that plant extracts added to fish feed can act as natural antimicrobial and immunostimulants to prevent pathogenic infection, enhance immune response, and promote growth of the fish.