Patient-derived Mammosphere and Xenograft Tumour Initiation Correlates with Progression to Metastasis

Abstract

Breast cancer specific mortality results from tumour cell dissemination and metastatic colonisation. Identification of the cells and processes responsible for metastasis will enable better prevention and control of metastatic disease, thus reducing relapse and mortality. To better understand these processes, we prospectively collected 307 patient-derived breast cancer samples (n = 195 early breast cancers (EBC) and n = 112 metastatic samples (MBC)). We assessed colony-forming activity in vitro by growing isolated cells in both primary (formation) and secondary (self-renewal) mammosphere culture, and tumour initiating activity in vivo through subcutaneous transplantation of fragments or cells into mice. Metastatic samples formed primary mammosphere colonies significantly more frequently than early breast cancers and had significantly higher primary mammosphere colony formation efficiency (0.9 % vs. 0.6 %; p < 0.0001). Tumour initiation in vivo was significantly higher in metastatic than early breast cancer samples (63 % vs. 38 %, p = 0.04). Of 144 breast cancer samples implanted in vivo, we established 20 stable patient-derived xenograft (PDX) models at passage 2 or greater. Lung metastases were detected in mice from 14 PDX models. Mammosphere colony formation in vitro significantly correlated with the ability of a tumour to metastasise to the lungs in vivo (p = 0.05), but not with subcutaneous tumour initiation. In summary, the breast cancer stem cell activities of colony formation and tumour initiation are increased in metastatic compared to early samples, and predict metastasis in vivo. These results suggest that breast stem cell activity will predict for poor outcome tumours, and therapy targeting this activity will improve outcomes for patients with metastatic disease.Electronic supplementary materialThe online version of this article (doi:10.1007/s10911-016-9361-8) contains supplementary material, which is available to authorized users.

Interrogating open issues in cancer precision medicine with patient-derived xenografts

“…2) For some cancer types, the ability of tumours to successfully engraft in mice can be considered per se a surrogate biomarker of risk for disease progression. For example, in mammary tumours, the ability to generate stable tumour grafts significantly predicted reduced survival 8,152 , and gene expression signatures associated with successful PDX engraftment correlated…”

Patient-derived xenograft (PDX) models in basic and translational breast cancer research

“…While impaired, presence of NK and macrophages in athymic and NOD/SCID mice can lead to elimination of tumor cells over time [132–134]. Use of this background has allowed take rates in excess of 20% on a routine basis (Table 3) (see [71,135,69,136] and Gomez-Miragaya et al, unpublished; Piwnica-Worms et al, unpublished).…”

“…Unfortunately, in addition to significant urinary tract complications associated with the use of estradiol-containing implants of all sorts, the major issue with this approach is that the implant becomes depleted of hormone over time, requiring periodic replacement if hormone levels are to be maintained long-term. To address these issues, several groups have revisited use of an old method by testing the ability of estradiol-supplemented drinking water for its ability to support PDX growth with promising results (Table 3) (see [68,165–168,136] Lewis et al, unpublished). Given the significant limitations of delivery using implants, estradiol-supplemented drinking water may be a superior method of delivery.…”

Current Update of Patient-Derived Xenograft Model for Translational Breast Cancer Research

“…It has not been clarified why human fibroblasts would stimulate tumor growth in normal human mammary tissue, but inhibit estradiol-enhanced growth in the PDX [19]. Interestingly, tumor tissue from a metastatic site has a higher engraftment rate in PDX models as compared to their localized primary tumors [20–22]. It is important to note that few studies have directly compared various implantation methods, thus the most appropriate method to generate PDX models with high levels of engraftment take rate (or survival?)…”

“…Most studies demonstrated that clinically relevant markers such as estrogen receptor (ER) and HER2 expression of PDX tumor are concordant with the source tissue by histological analysis [35, 31, 44, 19, 33, 40, 27, 28, 39, 20]. For instance, DeRose YS, et al demonstrated that the expression of clinically relevant molecular markers, such as ER, PR, and HER2 of primary source tumors were conserved in each PDX tumors of all 12 cases in their study [45].…”