Biomarkers of residual disease, disseminated tumor cells, and metastases in the MMTV-PyMT breast cancer model.

Christian Franci,Zora Modrusan,Erica Jackson,Jenny Zhou,Zinaida Good,Hosein Kouros-Mehr,Zhaoshi Jiang,Aamir Ahmed

doi:10.1371/journal.pone.0058183

Abstract

Cancer metastases arise in part from disseminated tumor cells originating from the primary tumor and from residual disease persisting after therapy. The identification of biomarkers on micro-metastases, disseminated tumors, and residual disease may yield novel tools for early detection and treatment of these disease states prior to their development into metastases and recurrent tumors. Here we describe the molecular profiling of disseminated tumor cells in lungs, lung metastases, and residual tumor cells in the MMTV-PyMT breast cancer model. MMTV-PyMT mice were bred with actin-GFP mice, and focal hyperplastic lesions from pubertal MMTV-PyMT;actin-GFP mice were orthotopically transplanted into FVB/n mice to track single tumor foci. Tumor-bearing mice were treated with TAC chemotherapy (docetaxel, doxorubicin, cyclophosphamide), and residual and relapsed tumor cells were sorted and profiled by mRNA microarray analysis. Data analysis revealed enrichment of the Jak/Stat pathway, Notch pathway, and epigenetic regulators in residual tumors. Stat1 was significantly up-regulated in a DNA-damage-resistant population of residual tumor cells, and a pre-existing Stat1 sub-population was identified in untreated tumors. Tumor cells from adenomas, carcinomas, lung disseminated tumor cells, and lung metastases were also sorted from MMTV-PyMT transplant mice and profiled by mRNA microarray. Whereas disseminated tumors cells appeared similar to carcinoma cells at the mRNA level, lung metastases were genotypically very different from disseminated cells and primary tumors. Lung metastases were enriched for a number of chromatin-modifying genes and stem cell-associated genes. Histone analysis of H3K4 and H3K9 suggested that lung metastases had been reprogrammed during malignant progression. These data identify novel biomarkers of residual tumor cells and disseminated tumor cells and implicate pathways that may mediate metastasis formation and tumor relapse after therapy.

Highlights

Metastases are the primary cause of morbidity and mortality in cancer patients
Focal hyperplasias were resected from 3-weekold mammary tumor virus (MMTV)-Polyoma Middle T-Antigen (PyMT);actin-green fluorescent protein (GFP) mice and orthotopically transplanted into the cleared mammary fat pads of FVB/n host mice (Figure 1A)
We modeled the clinical setting by administering the TAC chemotherapy regimen, which is given to patients with poorlydifferentiated breast adenocarcinoma [33]

Summary

Introduction

Metastases are the primary cause of morbidity and mortality in cancer patients. After diagnosis, cancer patients undergo a series of tests to determine their tumor stage, grade, molecular profile, and prognosis. Patients who are at risk of developing metastases at the time of diagnosis may undergo surgery, chemotherapy, radiotherapy, and/or targeted therapy to reduce the likelihood of tumor relapse and metastasis formation [4,5]. Breast cancer patients with no evidence of metastatic disease can have disseminated tumor cells in the bone marrow at the time of diagnosis [9]. These disseminated cells often exhibit fewer genomic aberrations than the primary tumor, suggesting that tumor dissemination can occur early during tumor formation [11]. Disseminated tumor cells often harbor marked genetic heterogeneity, making it difficult to target these populations with targeted therapy [13]

Methods

Results

Conclusion