Project description:Despite major advances in understanding the molecular and genetic basis of cancer, metastasis remains the cause of >90% of cancer-related mortality1. Understanding metastasis initiation and progression is critical to develop new therapeutic strategies to treat and prevent metastatic disease. Prevailing theories hypothesize that metastases are seeded by rare tumor cells with unique properties, which may function like stem cells in their ability to initiate and propagate metastatic tumors.2 3-5 However, the identity of metastasis-initiating cells in human breast cancer remains elusive, and whether metastases are hierarchically organized is unknown.2 Here we show at the single-cell level that early stage metastatic cells possess a distinct stem-like gene expression signature. To identify and isolate metastatic cells from patient-derived xenograft (PDX) models of human breast cancer, we developed a highly sensitive FACS-based assay, which allowed us to enumerate metastatic cells in mouse peripheral tissues. We compared gene signatures in metastatic cells from tissues with low vs. high metastatic burden. Metastatic cells from low-burden tissues were distinct due to their increased expression of stem cell, EMT, pro-survival, and dormancy-associated genes. In contrast, metastatic cells from high-burden tissues were similar to primary tumor cells, which were more heterogeneous and expressed higher levels of luminal differentiation genes. Transplantation of stem-like metastatic cells from low-burden tissues showed that they have significant tumor-initiating capacity, and differentiate to produce luminal-like cancer cells. Progression to high metastatic burden was associated with increased proliferation and cMYC expression, which could be attenuated by treatment with cyclin dependent kinase (CDK) inhibitors. These findings support a hierarchical model for metastasis, where metastases are initiated by stem-like cells that proliferate and differentiate to produce advanced metastatic disease.

Project description:Controlling metastatic lesions is an important part of improving cancer prognosis, in addition to controlling the primary lesion. There have been many histological examinations of primary and metastatic lesions, but little basic research using cell strains from primary and metastatic lesions belonging to the same patient. In this study, we successfully established a cell strain derived from lower gingival carcinoma (WK2) and a strain derived from secondary cervical lymph node metastasis (WK3F) through primary cultures of tissue from a patient with oral squamous cell carcinoma. We then investigated the biological characteristics of the cancer cell strains from these primary and metastatic lesions, and analyzed metastasis-related genes. Comparing the biological characteristics in vitro showed WK3F to have higher cell proliferation ability and shorter cell doubling time than WK2. It also showed increased cell migratory ability, and high invasive and self-replication abilities. Heterotransplantation into nude mice resulted in high tumor formation rates in the tongue and high metastasis rates in the cervical lymph nodes. Changes in WK2 and WK3F gene expression were comprehensively analyzed with the microarray method. Genes with increased expression in WK3F compared to WK2 were extracted when Z-score ≥ 2.0 and ratio ≥ 5.0, while genes with reduced expression in WK3F compared to WK2 were extracted when Z-score ≤ -2.0 and ratio ≤ 0.2. As a result, differences were found in 604 genes. From these, MAGEC1 (88.0 times), MMP-7 (18.6 times), SNAI1 (6.6 times), MACC1 (6.2 times), and HTRA1 (0.012 times) were selected as metastasis-related candidate genes. The results suggest that these molecules could be important to clarifying the mechanism of metastasis, and could become therapeutic targets. We successfully established a cell strain derived from lower gingival carcinoma (WK2) and a strain derived from secondary cervical lymph node metastasis (WK3F) through primary cultures of tissue from a patient with oral squamous cell carcinoma. Changes in WK2 and WK3F gene expression were comprehensively analyzed with the microarray method.

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Hope for Others: Research Results from the University of Pittsburgh Rapid Autopsy Program for Breast Cancer

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