ZR-75-1 Xenograft Model
Breast cancer affects 12% of women worldwide and is the most common invasive cancer type in women. In 2008 it caused almost half a million deaths worldwide which demonstrates the need for an improvement in treatment and breast cancer research. The ZR-75-1 cell line was isolated from a 63 year old female patient with ductal breast cancer. The ZR-75-1 model has been used in many breast cancer studies. In 1997 ZR-75-1 xenografts were used to evaluate the use of tamoxifen on breast cancer (Breast Cancer Research and Treatment, Cameron et al.). Results demonstrated that tamoxifen treatment does not affect necrosis but does increase apoptosis and decrease proliferation in ER negative (but not ER positive) cell lines. Tamoxifen today is a well-known anticancer treatment, although its use in early breast cancer was not established until 1998. A tamoxifen study in 1998 (Couillard et al., Cancer Research) also used the ZR-75-1 xenograft model to look at combination treatment with EM-800 antiestrogens. Data demonstrated that in the presence of estrogen (supplemented in ovariectomized (OVX) mice), tamoxifen treatment results in tumor growth stimulation whereas combination treatment with EM800 resulted in a synergistic decrease in tumor size. This has clinical relevance for predicting tamoxifen response based on estrogen levels as well as a potential method for amplifying the anticancer effect of tamoxifen. Kudoh et al. published a Cancer Research study (2002) using the ZR-75-1 cell line to investigate the role of Bag1 proteins in breast cancer. Bag1 proteins are known to interact with Hsp70 and regulate proliferation, stress response and apoptosis and are upregulated in breast cancer. Data demonstrated that Bag1 (and Bag1L) proteins increased survival in vitro and in vivo, providing evidence for the study of Bag1L for cancer treatment. The ZR-75-1 cell line is used to create the CDX (Cell Line Derived Xenograft) ZR-75-1 xenograft mouse model. The ZR-75-1 xenograft model has been used to evaluate anticancer therapies for breast cancer (including tamoxifen studies).
Basic Study Design:
- ZR-75-1 cells are maintained in exponential growth phase under aseptic conditions.
- Cells are trypsinized and cell count viability is determined using a trypan blue exclusion assay (98% of cell viability is required). ZR-75-1 cell suspension is adjusted to appropriate density.
- Each mouse is subcutaneously injected into the right flank with 106 cells in 100 µL of a Matrigel- ZR-75-1 cell suspension.
- The injection sites are palpated up to three times weekly until tumors are established to an average size of 50-150 mm3 as measured via digital calipers.
- Animals are randomized into treatment groups. Administration of test compound is performed according to the pre-established treatment schedule.
- Mice weights are measured and recorded 3 times weekly; tumors are measured and recorded daily.
- End of study is reached when tumor size reaches 2,000 mm3 or the predetermined size limit per approved IACUC protocol.
- Final necropsy and tissue collections are performed for appropriate downstream analysis. Tumors are excised, weighed and documented by digital imaging. Tumors and tissues can be stabilized in RNAlater, snap frozen in LN2 or prepared for histology.