Isolation and characterization of a metastatic hybrid cell line generated by ER negative and ER positive breast cancer cells in mouse bone marrow

The origin and the contribution of breast tumor heterogeneity to its progression are not clear. We investigated the effect of a growing orthotopic tumor formed by an aggressive estrogen receptor (ER)-negative breast cancer cell line on the metastatic potential of a less aggressive ER-positive breast cancer cell line for the elucidation of how the presence of heterogeneous cancer cells might affect each other’s metastatic behavior. ER positive ZR-75-1/GFP/puro cells, resistant to puromycin and non-tumorigenic/non-metastatic without exogenous estrogen supplementation, were injected intracardiacally into mice bearing growing orthotopic tumors, formed by ER negative MDA-MB-231/GFP/Neo cells resistant to G418. A variant cell line B6, containing both estrogen-dependent and -independent cells, were isolated from GFP expressing cells in the bone marrow and re-inoculated in nude mice to generate an estrogen-independent cell line B6TC.

乳腺肿瘤异质性的起源及其对肿瘤进展的贡献尚不明确。为阐明异质性癌细胞群如何相互调控彼此的转移行为，本研究探究了高侵袭性雌激素受体（ER）阴性乳腺癌细胞系形成的原位生长肿瘤，对低侵袭性ER阳性乳腺癌细胞系转移潜能的影响。
将耐嘌呤霉素（puromycin）、且在无外源性雌激素补充条件下无致瘤性与转移能力的ER阳性ZR-75-1/GFP/puro细胞，通过心腔内注射方式接种至已形成原位生长肿瘤的小鼠体内；该原位肿瘤由耐G418的ER阴性MDA-MB-231/GFP/Neo细胞形成。
从骨髓中表达绿色荧光蛋白（GFP）的细胞中分离出同时兼具雌激素依赖型与非依赖型特性的变异细胞系B6，随后将其重新接种至裸鼠（nude mice）体内，以构建得到雌激素非依赖型细胞系B6TC。