Malignant myoepithelial cells are associated with the differentiated papillary structure and metastatic ability of a syngeneic murine mammary adenocarcinoma model.
BACKGROUND
The normal duct and lobular system of the mammary gland is lined with luminal and myoepithelial cell types. Although evidence suggests that myoepithelial cells might suppress tumor growth, invasion and angiogenesis, their role remains a major enigma in breast cancer biology and few models are currently available for exploring their influence. Several years ago a spontaneous transplantable mammary adenocarcinoma (M38) arose in our BALB/c colony; it contains a malignant myoepithelial cell component and is able to metastasize to draining lymph nodes and lung.


METHODS
To characterize this tumor further, primary M38 cultures were established. The low-passage LM38-LP subline contained two main cell components up to the 30th subculture, whereas the higher passage LM38-HP subline was mainly composed of small spindle-shaped cells. In addition, a large spindle cell clone (LM38-D2) was established by dilutional cloning of the low-passage MM38-LP cells. These cell lines were studied by immunocytochemistry, electron microscopy and ploidy, and syngeneic mice were inoculated subcutaneously and intravenously with the different cell lines, either singly or combined to establish their tumorigenic and metastatic capacity.


RESULTS
The two subpopulations of LM38-LP cultures were characterized as luminal and myoepithelium-like cells, whereas LM38-HP was mainly composed of small, spindle-shaped epithelial cells and LM38-D2 contained only large myoepithelial cells. All of them were tumorigenic when inoculated into syngeneic mice, but only LM38-LP cultures containing both conserved luminal and myoepithelial malignant cells developed aggressive papillary adenocarcinomas that spread to lung and regional lymph nodes.


CONCLUSIONS
The differentiated histopathology and metastatic ability of the spontaneous transplantable M38 murine mammary tumor is associated with the presence and/or interaction of both luminal and myoepithelial tumor cell types.
Research Area, Institute of Oncology Angel H, Roffo, University of Buenos Aires, Argentina.
Viviana
V
Bumaschny
Alejandro
A
Urtreger
Miriam
M
Diament
Martín
M
Krasnapolski
Gabriel
G
Fiszman
Slobodanka
S
Klein
Elisa Bal de Kier
EB
Joffé
D000230:Adenocarcinoma / Q000201:enzymology / Q000235:genetics* / Q000556:secondary; D000231:Adenocarcinoma, Papillary / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000648:ultrastructure; D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology; D049109:Cell Proliferation; D004273:DNA, Neoplasm / Q000235:genetics; D004195:Disease Models, Animal; D008175:Lung Neoplasms / Q000235:genetics / Q000556:secondary; D008198:Lymph Nodes / Q000473:pathology; D008207:Lymphatic Metastasis / Q000235:genetics / Q000473:pathology; D015674:Mammary Neoplasms, Animal / Q000201:enzymology / Q000235:genetics* / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D046529:Microscopy, Electron, Transmission / Q000379:methods; D009208:Myoepithelioma / Q000235:genetics*; D009368:Neoplasm Transplantation / Q000379:methods; D010447:Peptide Hydrolases / Q000096:biosynthesis; D011003:Ploidies; D018874:Spheroids, Cellular / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; D010447:Peptide Hydrolases