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Unregulated smooth-muscle myosin in human intestinal neoplasia

Pia Alhopuro1, Denis Phichith, Sari Tuupanen

  • 1Department of Medical Genetics and Division of Pathology, HUSLAB and Haartman Institute, Helsinki University Central Hospital and Genome Scale Biology Program, Biomedicum Helsinki, University of Helsinki, 00014, Helsinki, Finland.

Proceedings of the National Academy of Sciences of the United States of America
|April 9, 2008
PubMed

Insights

Mutations in smooth muscle myosin (MYH11) cause intestinal abnormalities and cancer in zebrafish and humans. These MYH11 mutations lead to unregulated motor activity, contributing to intestinal neoplasia.

Area of Science:

  • Genetics and Molecular Biology
  • Cancer Research
  • Developmental Biology

Background:

  • A recessive mutation in smooth-muscle myosin (MYH11) causes the zebrafish meltdown (mlt) phenotype, characterized by intestinal abnormalities similar to human Peutz-Jeghers syndrome (PJS) and juvenile polyposis (JP).
  • The role of MYH11 in human intestinal neoplasia remains largely unexplored.

Purpose of the Study:

  • To investigate the presence and functional significance of MYH11 mutations in human intestinal neoplasia, including colorectal cancer (CRC), PJS, and JP.

Main Methods:

  • Screening for MYH11 mutations in patient cohorts with CRC, PJS, and JP.
  • Functional evaluation of identified MYH11 mutations (frameshift, missense) to assess their impact on protein activity.

Main Results:

  • Somatic protein-elongating frameshift mutations in MYH11 were found in 55% of microsatellite-instability-high CRCs.
  • Germline MYH11 mutations were identified in one PJS patient, and somatic missense mutations were found in one microsatellite-stable CRC.
  • All tested MYH11 mutations resulted in constitutively active, unregulated myosin motor activity.

Conclusions:

  • MYH11 mutations contribute to human intestinal neoplasia, challenging its role solely as a muscle contraction marker.
  • Unregulated MYH11 activity may disrupt cellular energy balance or progenitor cell lineage decisions in intestinal tumors.
  • These findings expand the understanding of the molecular mechanisms underlying intestinal neoplasia.

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