A rude awakening from tumour cells

Comparison of StemPrintER with Oncotype DX Recurrence Score for predicting risk of breast cancer distant recurrence after endocrine therapy

OBJECTIVE

Molecular tests predicting the risk of distant recurrence (DR) can be used to assist therapy decision-making in oestrogen receptor-positive (ER+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer patients after considerations of standard clinical markers. The Oncotype DX Recurrence Score (RS) is a widespread tool used for this purpose. Here, we compared the RS with the StemPrintER Risk Score (SPRS), a novel genomic predictor with a unique biological basis in its ability to measure the expression of cancer stemness genes.

MATERIALS AND METHODS

We benchmarked the SPRS vs. RS, alone or in combination with clinicopathological variables expressed by the Clinical Treatment Score (CTS), for the prognostication of DR in a retrospective cohort of 776 postmenopausal patients with ER+/HER2-breast cancer enrolled in the translational arm of the randomised Arimidex, Tamoxifen, Alone or in Combination (ATAC) trial. Likelihood ratio (LR) with χ² test and C-index were used to assess prognostic performance for the entire ten-year follow-up period and in early (0-5 years) and late (5-10 years) intervals.

RESULTS

In all patients, the SPRS provided significantly more prognostic information than the RS for ten-year DR prognostication (C-index = 0.688, LR-χ² = 33.4 vs. C-index = 0.641, LR-χ² = 22.1) and for late (5-10 years) DR prognostication (C-index = 0.689, LR-χ² = 18.8 vs. C-index = 0.571, LR-χ² = 4.7). The SPRS also provided more prognostic information than the RS when added to the CTS in all patients (CTS + SPRS: LR-Δχ² = 14.9; CTS + RS: LR-Δχ² = 9.7) and in node-negative patients (CTS + SPRS: LR-Δχ² = 11.7; CTS + RS: LR-Δχ² = 6.6).

CONCLUSIONS

In postmenopausal ER+/HER2- breast cancer patients, SPRS provided more prognostic information than RS for DR when used alone or in combination with the CTS. The SPRS could therefore potentially identify high-risk patients, who might benefit from aggressive treatments, from low-risk patients who might safely avoid adjuvant chemotherapy or prolongation of endocrine therapy.

Induction of dormancy by confinement: An agarose-silica biomaterial for isolating and analyzing dormant cancer cells

The principal cause of cancer deaths is the residual disease, which eventually results in metastases. Certain metastases are induced by disseminated dormancy-capable single cancer cells that can reside within the body undetected for months to years. Awakening of the dormant cells starts a cascade resulting in the patient's demise. Despite its established clinical significance, dormancy research and its clinical translation have been hindered by lack of in vitro models that can identify, isolate, and analyze dormancy-capable cells. We have previously shown that immobilization of cells in a stiff microenvironment induces dormancy in dormancy-capable cell lines. In this communication, we present a novel biomaterial and an in vitro immobilization method to isolate, analyze, and efficiently recover dormancy-capable cancer cells. MCF-7, MDA-MB-231, and MDA-MB-468 cells were individually coated with agarose using a microfluidic flow-focusing device. Coated cells were then immobilized in a rigid and porous silica gel. Dormancy induction by this process was validated by decreased Ki-67 expression, increased p38/ERK activity ratio, and reduced expression of CDK-2, cyclins D1, and E1. We showed that we can reliably and repeatedly induce dormancy in dormancy-capable MCF-7 cells and enhance the dormancy-capable sub-population in MDA-MB-231 cells. As expected, dormancy-resistant MDA-MB-468 cells did not survive immobilization. The dormant cells could be awakened on demand, by digesting the agarose gel in situ, and efficiently recovered by magnetically separating the silica gel, making the cells available for downstream analysis and testing. The awakened cells were shown to regain motility immediately, proliferating, and migrating normally.

Breast Cancer Stem Cells as Drivers of Tumor Chemoresistance, Dormancy and Relapse: New Challenges and Therapeutic Opportunities

Breast cancer is the most frequent cancer among women worldwide. Therapeutic strategies to prevent or treat metastatic disease are still inadequate although great progress has been made in treating early-stage breast cancer. Cancer stem-like cells (CSCs) that are endowed with high plasticity and self-renewal properties have been shown to play a key role in breast cancer development, progression, and metastasis. A subpopulation of CSCs that combines tumor-initiating capacity and a dormant/quiescent/slow cycling status is present throughout the clinical history of breast cancer patients. Dormant/quiescent/slow cycling CSCs are a key component of tumor heterogeneity and they are responsible for chemoresistance, tumor migration, and metastatic dormancy, defined as the ability of CSCs to survive in target organs and generate metastasis up to two decades after diagnosis. Understanding the strategies that are used by CSCs to resist conventional and targeted therapies, to interact with their niche, to escape immune surveillance, and finally to awaken from dormancy is of key importance to prevent and treat metastatic cancer. This review summarizes the current understanding of mechanisms involved in CSCs chemoresistance, dissemination, and metastasis in breast cancer, with a particular focus on dormant cells. Finally, we discuss how advancements in the detection, molecular understanding, and targeting of dormant CSCs will likely open new therapeutic avenues for breast cancer treatment.

Tumor dormancy at bedside: A late awakening

Breast cancer recurrence may occur at variable times following primary tumor removal. The corresponding event dynamics displays a structured multipeak pattern, which can be explained by the occurrence of microscopic phases of metastasis quiescence (tumor dormancy) followed by wake up, growth and timed clinical appearance. This model provides a meaningful justification of the early recurrence pattern and even explains the effectiveness of adjuvant systemic therapies. Yet, late recurrences, which were less investigated, are fairly little known and a few researchers supported their steady state appearance. We report here the analysis of the late clinical course from patients who were disease-free at 5 years of follow-up, which again displays a structured pattern, supporting the view that tumor dormancy can explain the late recurrence risk as well. Tailored treatments are needed to address late clinical recurrences.

Ten-year conditional recurrence risks and overall and relative survival for breast cancer patients in the Netherlands: Taking account of event-free years

BACKGROUND

Survival estimates from diagnosis are of limited importance for (ex-)breast cancer patients who survived several years, as it includes information on already deceased patients. This study analysed the 10-year conditional risk of recurrent breast cancer in specific prognostic subgroups. Second, we investigated 10-year conditional overall survival (OS) and relative survival (RS), adjusted for confounding.

PATIENTS AND METHODS

All women diagnosed in 2005 with operated T1-2N0-1 breast cancer were selected from the Netherlands Cancer Registry. Patients were classified into T1N0, T1N1, T2N0 and T2N1 stage. Ten-year conditional recurrence rates were calculated from diagnosis, and for patients without an event (local [LR], regional recurrence [RR], distant metastasis [DM] or death) every year following diagnosis. Ten-year conditional OS was calculated using multivariable Cox regression. RS was estimated by dividing patient survival rates by those of the general Dutch population.

RESULTS

We included 7969 patients: 52.3% had T1N0, 15.3% T1N1, 19.9% T2N0 and 12.5% T2N1 stage. For T1N0, 10-year LR rates changed from 4.6% at diagnosis to 0.5% in year 10. RR rates changed from 2.3% to 0.2%, and DM rates changed from 7.8% to 0.6%. For T2N1 stage, the LR, RR and DM rates changed from 6.2% to 0.8%, 5.2%-0.4% and 19.6%-1.5%, respectively. For the luminal A subtype, LR, RR and DM rates changed from 3.9% to 0.4%, 1.7%-0.5% and 7.3%-1.1%, while for triple negative, these rates changed from 5.6% to 0.7%, 4.9%-0.2% and 16.7%-0%, respectively. Differences between subgroups attenuated over time, and all recurrence rates became ≤1.5% in year 10. Ten-year OS and RS, adjusted for confounding, showed declining risk differences between subgroups over time.

CONCLUSION

Differences in recurrence rates, OS and RS between prognostic subgroups declined as years passed by. These results highlight the importance of taking into account disease-free years to more accurately predict (ex-)breast cancer patients' prognosis over time.