Histopathologic findings and establishment of novel tumor linesfrom spontaneous tumors in FVB/N mice

The inbred FVB mouse strain is used extensively in cancer research. Transgenic mice with an FVB/N background in which the expression of green fluorescent protein is under the control of various promoters have been used widely for the last decade. However, little is known about the incidence and characteristics of spontaneous tumors in these mice. In addition, only a few tumor lines have been established for use in this particular mouse strain. Our aim was to initiate a database of spontaneous tumors in our retired FVB/N breeders, analyze the histopathologic characteristics of these tumors, and establish novel tumor lines in vivo and in vitro. A total of 234 (40 male, 194 female) breeder mice were observed during their natural lifespans. The incidence of spontaneous tumors was 45.0% in male mice and 52.8% in female mice. All tumors in male mice were lung alveolar-bronchiolar (AB) neoplasms, except for 1 testis interstitial cell tumor. In female mice, histopathologic examination revealed 48 lung AB tumors, 27 mammary gland tumors, 13 ovarian tumors, and 14 other tumors. Several of these spontaneous tumors have been transplanted into FVB/N mice. One mammary adenocarcinoma (MCaP0008) and 1 lung AB carcinoma (LAP0297) were successfully transplanted subcutaneously and passaged serially in vivo. Subsequently, we established cell lines from both tumors, which were maintained in monolayer in vitro. Both of the grafted tumors and cell lines are tumorigenic in VEGF^P-GFP/FVB and Tie2^P-GFP/FVB mice. Establishment of these novel tumor lines will benefit both in vivo and in vitro studies on the pathophysiology of cancer in this relatively new but widely used mouse strain.