Generation and characterisation of an estrogen receptor-positive GEMM-derived Pten p53 null transplantable breast tumour model for therapeutic testing

Assessing the signalling pathway dependencies of tumours that arise autochthonously in genetically engineered mouse models (GEMMs) of breast cancer is particularly challenging due to the high degree of intra- and inter-tumour heterogeneity, as well as the long latency of tumour development in such models. Use of transplantable tumour lines derived from autochthonous tumours (‘Mouse Derived Xenografts’ or MDXs) is one possible solution and has been used successfully in models of BRCA1-associated triple negative breast cancer. However, their potential in ER+ breast cancer models has not been addressed. Here, we assess the utility of orthotopic transplantable tumour lines derived from an autochthonous ER+ Blg-cre Ptenfl/fl p53fl/fl breast cancer model. We show that initial tumour implantation and early passage results in the development of lines of progeny with heterogeneous histopathological phenotypes which is coincident with an accumulation of, or selection for, de novo mutations. Importantly, these lines also display different dependencies on the key pathways that drive tumourigenesis, which can lead to inherent resistance to treatment with pharmacological agents targeting these pathways and makes them important models to test strategies to overcome such resistance.

Chromatographic characteristics of pro-opiomelanocortin-derived peptides from the rat transplantable tumour 7315a

ABSTRACT Adrenocorticotrophin (ACTH) and other proopiomelanocortin (POMC)-derived peptides produced by the 7315a corticomammotrophic tumour have been poorly studied although they elicit profound hypertrophy and hyperplasia in the adrenal glands of recipient Buffalo rats. Tumour extracts were chromatographed on Sephadex G-75 and fractions monitored for POMC-derived peptides by four radioimmunoassay (RIA) systems: ACTH, α-MSH, β-lipotrophin (β-LPH)/endorphin and N-terminal POMC (N-POMC). Chromatograms were compared with those of pars distalis extracts from normal Buffalo rats. All four RIA systems detected immunoreactive material in tumour extracts. ACTH, β-LPH/ endorphin and N-POMC were present in approximately equimolar amounts (ACTH content 93·40 ± 5·27 (s.e.m.) pmol/g) whereas α-MSH was present in smaller amounts (2·83± 0·13 pmol/g). Total peptide content correlated well with tumour weight. ACTH immunoreactivity (IR) in Sephadex chromatograms was located in a large 20 000 mol. wt peak, an ACTH(1–39) peak and a smaller peak coinciding with ACTH(1–24). The latter two peaks showed biological activity consistent with ACTH(1–39) and an ACTH (1–24)-like peptide respectively. The β-LPH/endorphin RIA revealed a peak eluting at approximately 20 000 mol. wt which could not be ascribed to any known POMC peptide containing the endorphin sequence. A β-LPH-like peak, a β-endorphin-like peak and a smaller-sized peak, which contained the bulk of the β-LPH/endorphin IR, were detected; the low molecular weight peak probably representing α- or γ-endorphin. The N-POMC RIA revealed a 20 000 mol. wt peak and a wide peak which could not be completely resolved into two peaks, and which probably represented N-POMC(1–95) and (N-POMC(1–74). No 30 000 mol. wt precursor could be detected with any of the RIA systems employed. Sephadex chromatography of material released from perfused dispersed tumour cells revealed identical IR peaks with all RIA systems used. Glycosylation of tumour POMC peptides was assessed by Concanavalin A–agarose (Con A) chromatography of pooled IR peaks from Sephadex chromatograms. The 20 000 mol. wt (both IR-ACTH and IR-N-POMC) peak, IR-N-POMC(1–95) and IR-N-POMC(1–74) peaks all bound to Con A and were specifically eluted with methylglucoside. Sephadex G-75 and Con A chromatography of pooled pars distalis extracts from normal Buffalo rats were performed. They showed significant differences, compared with tumour extract chromatograms, with all the RIA systems employed. It is concluded that the 7315a tumour processes POMC in a different manner when compared with normal Buffalo rat pars distalis and that it may be used as an interesting model in which to study the processing of POMC. In addition it may shed light on the role of POMC-derived peptides, other than ACTH(1–39), on adrenal growth and function. J. Endocr. (1987) 112, 417–425

Establishment of a continuous somatostatin-producing line of medullary thyroid carcinoma cells from BALB/c mice

ABSTRACT A continuous line of somatostatin-producing medullary thyroid carcinoma cells was established from a transplantable tumour in BALB/c mice. Virtually all of the somatostatin immunoreactivity co-chromatographed with somatostatin 14. The tumour cells replicated in spinner cultures with a doubling time of approximately 4 days, and the concentration of somatostatin released into the culture medium increased in proportion to the number of cells. Two-to threefold increases in amounts of stored and released somatostatin were observed after treatment of the cells with bromodeoxyuridine. This cell line might be valuable for studies of somatostatin regulation in normal and neoplastic C-cells, and for other studies of C-cell biology which require a mouse model. J. Endocr. (1986) 110, 309–313