Specificity of antibodies against rodent transforming growth factor-alpha protein

Characterization of uterine leiomyomas in CD-1 mice following developmental exposure to diethylstilbestrol (DES)

Experimental animal and clinical studies have well established the association of prenatal exposure to diethylstilbestrol (DES) and the subsequent development of reproductive tract abnormalities, including poor reproductive outcome and neoplasia. Overwhelmingly, the focus has been on DES-induced epithelial lesions, particularly vaginal adenosis and adenocarcinoma; however, uterine smooth muscle cells are also recognized as cellular targets of DES. This descriptive report characterizes uterine leiomyomas that occur in outbred CD-1 mice following exposure to DES prenatally on days 9 to 16 of gestation or on neonatal days 1 to 5. These DES-induced uterine leiomyomas have typical histomorphologic, and some immunohistochemical characteristics of spontaneously occurring uterine smooth muscle tumors of B6C3F1 mice previously described in our laboratory, and they are also similar to uterine leiomyomas (fibroids) commonly observed in premenopausal women.

Immortalization of human uterine leiomyoma and myometrial cell lines after induction of telomerase activity: molecular and phenotypic characteristics

In vitro model systems for studying uterine leiomyomas are limited in that human-derived leiomyoma cells grow poorly in culture compared with normal myometrial cells and begin to senesce early, at approximately passage 10 in our studies. To our knowledge, a good in vitro human-derived cell culturing system for leiomyomas does not exist. In an attempt to fill this void, we have immortalized a uterine leiomyoma cell line by inducing telomerase activity, which allows cells to bypass their normal programmed senescence. Telomerase activity was induced by infecting the target (uterine leiomyoma and normal myometrial) cells with a retroviral vector containing hTERT, the gene for the catalytic subunit of telomerase. Subsequent analysis by RT-PCR and the telomeric repeat amplification protocol assay confirmed expression of the inserted gene and induction of telomerase activity in leiomyoma and myometrial cells. Analysis of cells for estrogen receptor-alpha and progesterone receptor proteins by Western blotting showed no change in expression of these proteins between the immortalized and parental leiomyoma and myometrial cells. Both immortalized and parental myometrial and leiomyoma cells expressed the smooth muscle-specific cytoskeletal protein alpha-actin and were negative for mutant p53 protein as evidenced by immunocytochemical staining. The immortalized leiomyoma and myometrial cells showed no anchorage-independent growth, with the exception of a small subpopulation of immortalized leiomyoma cells at a higher passage that did form two to three small colonies (per 50,000 cells) in soft agar. None of the immortalized cells were tumorigenic in nude mice. In conclusion, our data show the successful insertion of the hTERT gene into leiomyoma and myometrial cells and the immortalization of these cell lines without phenotypic alteration from the parental cell types (up to 200 population doublings). These cells should help to advance research in understanding the molecular pathways involved in the conversion of a normal myometrial cell to a leiomyoma cell and the mechanisms responsible for the growth of uterine leiomyomas. Answers to these questions will undoubtedly lead to the development of more effective treatment and intervention regimens for clinical cases of uterine leiomyoma.

Transforming growth factor-alpha, epidermal growth factor receptor, and PCNA immunoexpression in uterine leiomyosarcomas and leiomyomas in B6C3F1 mice

The role of growth factors in the development of murine uterine mesenchymal tumors is unknown. In this study, immunohistochemical expression of transforming growth factor alpha (TGF-alpha) and its receptor epidermal growth factor (EGF-R) was assessed in spontaneous uterine leiomyomas and leiomyosarcomas in B6C3F1 mice. Cell proliferation, which has been induced by some growth factors, was evaluated by immunohistochemical detection of an endogenous marker of cell proliferation, proliferating cell nuclear antigen (PCNA). PCNA labeling indices were determined and compared to the intensity and distribution of TGF-alpha staining in sequential sections of control myometrium or tumor tissue. Results showed uterine leiomyosarcomas had positive cytoplasmic staining for TGF-alpha; however, all uterine leiomyomas evaluated were negative. Positive EGF-R staining was also observed in the uterine leiomyosarcomas, but not in the leiomyomas. EGF-R immunoexpression was detected primarily within the cytoplasm of the leiomyosarcoma cells, with occasional nuclear immunoreactivity. Immunohistochemical staining for PCNA was more intense and there were increased numbers of positively staining nuclei in the leiomyosarcomas compared to samples of control myometrium or leiomyomas. The mean labeling index for the uterine leiomyosarcomas (7.40%) was significantly (p < 0.01) higher than that of leiomyomas (0.29%) and control uterine myometrium (0.13%). We conclude, that TGF-alpha and its receptor, EGF-R, are expressed more intensely in uterine leiomyosarcomas, compared to leiomyomas in B6C3F1 mice. Immunoexpression of TGF-alpha may be an important biomarker of malignancy in uterine smooth muscle tumors in mice. Futhermore, TGF-alpha may play a critical role in increased proliferation of uterine smooth muscle tumor cells as suggested by increased immunolocalization of PCNA in rodent leiomyosarcomas expressing TGF-alpha, although other factors regulating cell replication can not be ruled out.

Specificity of the localization of transforming growth factor-alpha immunoreactivity in colon mucosa

Transforming growth factor-alpha (TGF-alpha) plays an important role in gastrointestinal pathophysiology. However, the exact location of its expression in the intestine is still controversial. This study systematically compared the localization of TGF-alpha immunoreactivity in frozen or fixed human colon using three different antibodies and examined specificity of antibodies by using tissues from TGF-alpha knockout mice and by Western blotting. Consistent with the mRNA distribution revealed by in situ hybridization, a similar staining pattern was obtained in frozen sections by all three antibodies, localizing on the surface and along the crypt epithelium. In paraffin sections, although the polyclonal antibodies (raised against recombinant human or rat TGF-alpha) gave minimal staining, the monoclonal antibody (against C-terminal peptide of human TGF-alpha) still gave intense staining on the surface and upper crypt epithelium. By using specimens from TGF-alpha knockout mice in immunostaining and Western blotting, the polyclonal antibodies were shown to be specific. In contrast, specificity of the monoclonal antibody was in doubt in rodent tissues because it gave similar detection between wild-type and knockout mice in both analyses, indicating its crossreaction to non-TGF-alpha molecules. In conclusion, frozen sections and antibodies raised from recombinant TGF-alpha should be used for TGF-alpha immunohistochemistry in the colon.