Somatic cell origin of teratocarcinomas.

Area of Science:

• Developmental biology
• Cancer research
• Stem cell biology

Background:

• Malignant teratocarcinomas arise from developmentally totipotent stem cells, but their origin (somatic vs. germ cells) is debated.
• Previous studies on teratocarcinoma induction were ambiguous due to germ cell formation in embryos and parthenogenesis.

Purpose of the Study:

• To determine if malignant teratocarcinomas originate from embryonal somatic cells or germ cells.
• To investigate the role of stem cell totipotency in teratocarcinoma development.

Main Methods:

• Grafting of day 6 mouse embryos from genetically sterile strains (S1(J)/S1(J) and W/W) to interrupt development.
• Utilizing a phosphoglucomutase (PGM) marker to identify tumors from sterile W/W embryos.
• Analyzing tumor formation and cellular content in grafted embryos.

Main Results:

• Tumors containing embryonal carcinoma cells formed in grafts of sterile S1(J)/S1(J) embryos at a rate comparable to controls.
• Tumors from sterile W/W embryos, identified by PGM-1D phenotype, also contained embryonal carcinoma cells.
• These findings indicate malignancy arises in somatic embryonal stem cells nearing the end of their totipotent stage.

Conclusions:

• Malignant teratocarcinomas arise from somatic embryonal stem cells that have reached the threshold of differentiation.
• This suggests a general model where stem cell differentiation state is critical for neoplastic transformation.
• Other teratocarcinomas, even those appearing to originate from germ cells, may involve these somatic stem cells prior to malignancy.