Spheroid-plug model as a tool to study tumor development, angiogenesis, and heterogeneity in vivo

Subcutaneous injection of the tumor cell suspension is a simple and commonly used tool for studying tumor development in vivo. However, subcutaneous models poorly resemble tumor complexity due to the fast growth not reflecting the natural course. Here, we describe an application of the new spheroid-plug model to combine the simplicity of subcutaneous injection with improved resemblance to natural tumor progression. Spheroid-plug model relies on in vitro formation of tumor spheroids, followed by injection of single tumor spheroid subcutaneously in Matrigel matrix. In spheroid-plug model, tumors grow slower in comparison to tumors formed by injection of cell suspension as assessed by 3D ultrasonography (USG) and in vivo bioluminescence measurements. The slower tumor growth rate in spheroid-plug model is accompanied by reduced necrosis. The spheroid-plug model ensures increased and more stable vascularization of tumor than classical subcutaneous tumor model as demonstrated by 3D USG Power Doppler examination. Flow cytometry analysis showed that tumors formed from spheroids have enhanced infiltration of endothelial cells as well as hematopoietic and progenitor cells with stem cell phenotype (c-Kit+ and Sca-1+). They also contain more tumor cells expressing cancer stem cell marker CXCR4. Here, we show that spheroid-plug model allows investigating efficiency of anticancer drugs. Treatment of spheroid-plug tumors with known antiangiogenic agent axitinib decreased their size and viability. The antiangiogenic activity of axitinib was higher in spheroid-plug model than in classical model. Our results indicate that spheroid-plug model imitates natural tumor growth and can become a valuable tool for cancer research

One-step immortalization of primary human airway epithelial cells capable of oncogenic transformation

BACKGROUND: The ability to transform normal human cells into cancer cells with the introduction of defined genetic alterations is a valuable method for understanding the mechanisms of oncogenesis. Easy establishment of immortalized but non-transformed human cells from various tissues would facilitate these genetic analyses. RESULTS: We report here a simple, one-step immortalization method that involves retroviral vector mediated co-expression of the human telomerase protein and a shRNA targeting the CDKN2A gene locus. We demonstrate that this method could successfully immortalize human small airway epithelial cells while maintaining their chromosomal stability. We further showed that these cells retain p53 activity and can be transformed by the KRAS oncogene. CONCLUSIONS: Our method simplifies the immortalization process and is broadly applicable for establishing immortalized epithelial cell lines from primary human tissues for cancer research

Expression of ALDH1 in axillary lymph node metastases is a prognostic factor of poor clinical outcome in breast cancer patients with 1–3 lymph node metastases

Background Recently, evidence in support of the cancer stem cell (CSC) hypothesis has been accumulating. On the other hand, it has been reported that the expression of aldehyde dehydrogenase 1 (ALDH1) in primary breast cancer is a powerful predictor of a poor clinical outcome, and that breast cancer stem cells express ALDH1. According to the CSC hypothesis, development of metastases requires the dissemination of CSC that may remain dormant and be reactivated to cause tumor recurrence. In this study, we investigated whether the detection of CSC in axillary lymph node metastases (ALNM) might be a significant prognostic factor in patients with breast cancer. Methods From 1998 to 2006, 40 primary breast cancer patients with ALNM, the number of metastatic nodes varying in number from 1 to 3, underwent surgery at Okayama University; of these, 15 patients developed tumor recurrence. We retrospectively evaluated the common clinicopathological features and the expression of ER, HER2, ALDH1, and Ki67 in both the primary lesions and the ALNM, and analyzed the correlations between the expression of these biological markers and the disease-free survival (DFS). Results Expression of ALDH1 in the ALNM was significantly associated with the DFS (P = 0.037). Conclusion Evaluation of biomarker expression in ALNM could be useful for prognosis in breast cancer patients with 1–3 metastatic lymph nodes

Reconstructing lineage hierarchies of the distal lung epithelium using single-cell RNA-seq

The mammalian lung is a highly branched network, in which the distal regions of the bronchial tree transform during development into a densely packed honeycomb of alveolar air sacs that mediate gas exchange. Although this transformation has been studied by marker expression analysis and fate-mapping, the mechanisms that control the progression of lung progenitors along distinct lineages into mature alveolar cell types remain obscure, in part due to the limited number of lineage markers(1)-(3) and the effects of ensemble averaging in conventional transcriptome analysis experiments on cell populations(1)–(5). We used microfluidic single cell RNA sequencing (RNA-seq) on 198 individual cells at 4 different stages encompassing alveolar differentiation to measure the transcriptional states which define the developmental and cellular hierarchy of the distal mouse lung epithelium. We empirically classified cells into distinct groups using an unbiased genome-wide approach that did not require a priori knowledge of the underlying cell types or prior purification of cell populations. The results confirmed the basic outlines of the classical model of epithelial cell type diversity in the distal lung and led to the discovery of many novel cell type markers and transcriptional regulators that discriminate between the different populations. We reconstructed the molecular steps during maturation of bipotential progenitors along both alveolar lineages and elucidated the full lifecycle of the alveolar type 2 cell lineage. This single cell genomics approach is applicable to any developing or mature tissue to robustly delineate molecularly distinct cell types, define progenitors and lineage hierarchies, and identify lineage-specific regulatory factors