Tumor angiogenesis is necessary for solid tumor progression and metastasis. Tumor blood vessels have been shown to differ from normal counterparts, for example, by changes in morphology. An important concept in tumor angiogenesis is that tumor endothelial cells are assumed to be genetically normal, although these endothelial cells are structurally and functionally abnormal. However, we hypothesized that given the phenotypic differences between tumor and normal blood vessels, there may be genotypic alterations as well. Mouse endothelial cells were isolated from two different human tumor xenografts, melanoma and liposarcoma, and from two normal endothelial cell counterparts, skin and adipose. Tumor-associated endothelial cells expressed typical endothelial cell markers, such as CD31. They had relatively large, heterogeneous nuclei. Unexpectedly, tumor endothelial cells were cytogenetically abnormal. Fluorescence in situ hybridization (FISH) analysis showed that freshly isolated uncultured tumor endothelial cells were aneuploid and had abnormal multiple centrosomes. The degree of aneuploidy was exacerbated by passage in culture. Multicolor FISH indicated that the structural chromosomal aberrations in tumor endothelial cells were heterogeneous, indicating that the cytogenetic alterations were not clonal. There was no evidence of human tumor-derived chromosomal material in the mouse tumor endothelial cells. In marked contrast, freshly isolated normal skin and adipose endothelial cells were diploid, had normal centrosomes, and remained cytogenetically stable in culture even up to 20 passages. FISH analysis of tumor sections also showed endothelial cell aneuploidy. We conclude that tumor endothelial cells can acquire cytogenetic abnormalities while in the tumor microenvironment.

OBJECTIVE: Thrombus in the stump of the pulmonary vein (PV) is not a well-known complication after lung resection, and it has the potential to cause embolism to vital organs. To clarify the frequency, risk factors, and cause of this complication, a retrospective clinical study of patients who underwent lobectomy was performed.METHOD: The subjects were 193 patients with primary lung cancer who underwent lobectomy from 2005 to 2011 and contrast-enhanced chest CT within 2 years after lobectomy. Contrast-enhanced CT was retrospectively interpreted to check for thrombus in the PV stump.RESULTS: The operative procedures were 65 right upper lobectomies, 14 right middle lobectomies, 40 right lower lobectomies, 52 left upper lobectomies (LUL), and 22 left lower lobectomies. Of the 193 patients, 7 (3.6%) developed thrombus in the PV stump after lobectomy. All patients with thrombus had undergone LUL, and 13.5% of those who had undergone LUL developed thrombus. Univariate analyses revealed that LUL and operation time were significant risk factors, and that adjuvant chemotherapy was marginally significant. It appears that thrombus may be attributable to the length of the PV stump. Measurement of the length of the PV stump using three-dimensional CT images of the PV revealed that the stump of the left superior PV was longer than the others.CONCLUSION: Thrombus in the PV stump occurred in 13.5% of cases after LUL. These findings suggest that contrast-enhanced CT should be recommended for patients after LUL to help identify patients with a high risk for thromboembolism.(246 words)

Tumor metastasis is the main cause of cancer‐related death. Understanding the molecular mechanisms underlying tumor metastasis is crucial to control this fatal disease. Several molecular pathways orchestrate the complex biological cell events during a metastatic cascade. It is now well known that bidirectional interaction between tumor cells and their microenvironment, including tumor stroma, is important for tumor progression and metastasis. Tumor stromal cells, which acquire their specific characteristics in the tumor microenvironment, accelerate tumor malignancy. The formation of new blood vessels, termed as tumor angiogenesis, is a requirement for tumor progression. Tumor blood vessels supply nutrients and oxygen and also provide the route for metastasis. Tumor endothelial cells, which line tumor blood vessels, also exhibit several altered phenotypes compared with those of their normal counterparts. Recent studies have emphasized “angiocrine factors” that are released from tumor endothelial cells and promote tumor progression. During intravasation, tumor cells physically contact tumor endothelial cells and interact with them by juxtacrine and paracrine signaling. Recently, we observed that in highly metastatic tumors, tumor endothelial cells interact with tumor cells by secretion of a small leucine‐rich repeat proteoglycan known as biglycan. Biglycan from tumor endothelial cells stimulates the tumor cells to metastasize. In the present review, we highlight the role of tumor stromal cells, particularly endothelial cells, in the initial steps of tumor metastasis.

Tumor blood vessels are thought to contain genetically normal and stable endothelial cells (ECs), unlike tumor cells, which typically display genetic instability. Yet, chromosomal aberration in human tumor-associated ECs (hTECs) in carcinoma has not yet been investigated. Here we isolated TECs from 20 human renal cell carcinomas and analyzed their cytogenetic abnormalities. The degree of aneuploidy was analyzed by fluorescence in situ hybridization using chromosome 7 and chromosome 8 DNA probes in isolated hTECs. In human renal cell carcinomas, 22-58% (median, 33%) of uncultured hTECs were aneuploid, whereas normal ECs were diploid. The mechanisms governing TEC aneuploidy were then studied using mouse TECs (mTECs) isolated from xenografts of human epithelial tumors. To investigate the contribution of progenitor cells to aneuploidy in mTECs, CD133(+) and CD133(-) mTECs were compared for aneuploidy. CD133(+) mTECs showed aneuploidy more frequently than CD133(-) mTECs. This is the first report showing cytogenetic abnormality of hTECs in carcinoma, contrary to traditional belief. Cytogenetic alterations in tumor vessels of carcinoma therefore can occur and may play a significant role in modifying tumor- stromal interactions.

Tumour blood vessels are gateways for distant metastasis. Recent studies have revealed that tumour endothelial cells (TECs) demonstrate distinct phenotypes from their normal counterparts. We have demonstrated that features of TECs are different depending on tumour malignancy, suggesting that TECs communicate with surrounding tumour cells. However, the contribution of TECs to metastasis has not been elucidated. Here, we show that TECs actively promote tumour metastasis through a bidirectional interaction between tumour cells and TECs. Co-implantation of TECs isolated from highly metastatic tumours accelerated lung metastases of low metastatic tumours. Biglycan, a small leucine-rich repeat proteoglycan secreted from TECs, activated tumour cell migration via nuclear factor-κB and extracellular signal–regulated kinase 1/2. Biglycan expression was upregulated by DNA demethylation in TECs. Collectively, our results demonstrate that TECs are altered in their microenvironment and, in turn, instigate tumour cells to metastasize, which is a novel mechanism for tumour metastasis.