Is xenotransplantability of human colon cancers in SCID mice affected by angiogenic factors?

Correlation between tumor engraftment in patient-derived xenograft models and clinical outcomes in colorectal cancer patients

Despite numerous studies involving patient-derived xenograft (PDX) models, few studies have investigated the relationship between the ability of the tumor to engraft (tumorigenicity) and the clinical features of colorectal cancer (CRC). The aim of this study was to determine whether tumorigenicity correlates with clinical outcomes of CRC patients. We included 241 CRC patients who underwent radical surgery from 2010 to 2013. PDX models were established by implanting tumor fragments obtained from these patients into the subcutaneous layer of immunodeficient mice. Xenografts were successfully established from 62.2%. Successful engraftment was associated with advanced stage (p < 0.001) and moderate/poor differentiation (p = 0.029). Three-year disease-free survival (DFS) rates were lower for patients with tumorigenicity (p = 0.011). In stage III patients, tumorigenicity was an independent predictor of poor DFS (p = 0.034). In addition, mutation of TP53 was most frequently detected in stage III patients with tumorigenicity. Two models of stage IV disease without KRAS mutations showed high sensitivity to EGFR-targeted agents, while none of the models with KRAS mutations showed high sensitivity. In conclusion, PDX models may provide an effective preclinical tool for predicting cancer progression and could be used to further genomic and pharmacologic research on personalized treatments.

Establishment of patient-derived cancer xenografts in immunodeficient NOG mice

Viable and stable human cancer cell lines and animal models combined with adequate clinical information are essential for future advances in cancer research and patient care. Conventional in vitro cancer cell lines are commonly available; however, they lack detailed information on the patient from which they originate, including disease phenotype and drug sensitivity. Patient-derived xenografts (PDX) with clinical information (so-called ‘cancer xenopatients’) are a promising advance that may accelerate the development of anticancer therapies. We established 61 PDX lines from 116 surgically removed tumor tissues inoculated subcutaneously into NOG mice (53% success rate). PDX lines were established from various types of epithelial tumors and also from sarcomas, including gastrointestinal stromal tumors and Ewing/PNET sarcomas. The metastatic tumors yielded PDX lines more effectively (65%) than the primary tumors (27%, P<0.001). In our PDX models, morphological characteristics, gene expression profiles, and genetic alteration patterns were all well preserved. In eight cases (7%), the transplantable xenografts for several generations were composed of large monotonous nonepithelial cells of human origin, revealed to be Epstein-Barr virus infection-associated lymphoproliferative lesions. Despite this, PDX linked with clinical information offer many advantages for preclinical studies investigating new anticancer drugs. The fast and efficient establishment of individual PDX may also contribute to future personalized anticancer therapies.

Identification of an exonic splicing silencer in exon 6A of the human VEGF gene

Background

The different isoforms of vascular endothelial growth factor (VEGF) play diverse roles in vascular growth, structure and function. Alternative splicing of the VEGF gene results in the expression of three abundant isoforms: VEGF121, VEGF165 and VEGF189. The mRNA for VEGF189 contains the alternatively spliced exon 6A whereas the mRNA for VEGF165 lacks this exon. The objective of this study was to identify the cis elements that control utilization of exon 6A. A reporter minigene was constructed (pGFP-E6A) containing the coding sequence for GFP whose translation was dependent on faithful splicing for removal of the VEGF exon 6A. To identify cis-acting splicing elements, sequential deletions were made across exon 6A in the pGFP-E6A plasmid.

Results

A candidate cis-acting exonic splicing silencer (ESS) comprising nucleotides 22-30 of exon 6A sequence was identified corresponding to the a silencer consensus sequence of AAGGGG. The function of this sequence as an ESS was confirmed in vivo both in the context of the reporter minigene as a plasmid and in the context of a longer minigene with VEGF exon 6A in its native context in an adenoviral gene transfer vector. Further mutagenesis studies resulted in the identification of the second G residue of the putative ESS as the most critical for function.

Conclusion

This work establishes the identity of cis sequences that regulate alternative VEGF splicing and dictate the relative expression levels of VEGF isoforms.

Establishment and characterization of in vivo human tumor models in the NOD/SCID/gamma(c)(null) mouse

Immunodeficient mice are widely used for xenografts of human cells and tissue. The purpose of the present study was to investigate the characteristics of xenograft human tumor models using engraftment of various non-hematopoietic tumors in the NOD/SCID/gamma(c) (null) mouse. For tumor models, human solid tumor tissues were serially passaged three or more times to establish tissue lines. A total of 326 fresh tumor specimens, mainly gastrointestinal and female genital tissue, were engrafted with 54 established tissue lines. The types of tissue lines varied and included tumor tissue of both epithelial and mesenchymal origin. In some cases the original surgical specimen was replaced with large mononuclear cells. In the established tumor tissue lines, differentiation and tumor structure were similar to that of the original surgical specimen. The interstitium of the xenograft tissue in the tissue lines was relatively well preserved although slightly decreased and replaced by host tissue. These results indicate that human solid tumors can be successfully engrafted into the NOD/SCID/gamma(c) (null) mouse and that tissue lines with the characteristics of the original tumors can be established. Investigators in the field of tumor research will benefit from the availability of tissue lines that allow the establishment of more relevant in vivo human tissue models.

Neuropilin 1 and neuropilin 2 co-expression is significantly correlated with increased vascularity and poor prognosis in nonsmall cell lung carcinoma

BACKGROUND

Cell-retained isoforms of vascular endothelial growth factor A (VEGF-A) have been reported to play an essential role in tumor progression through stromal neovascularization in malignant solid tumors. While more than 95% of nonsmall cell lung carcinoma (NSCLC) expresses cell-retained VEGF-A isoform, the clinicopathologic implications of neuropilin (NRP), considered the specific receptor for limited types of VEGF-A isoform, are not well understood.

METHODS

The authors examined NRP1 and NRP2 mRNA expression in 68 NSCLCs and 15 extraneoplastic tissues by a densitometry-assisted, semi-quantitative reverse transcription-polymerase chain reaction. The authors determined the distinct expression of NRPs using the expression level of NRPs relative by optical density to beta2-microglobulin. The authors also investigated VEGF-A isoforms, their receptors, and the clinical implications. Vascularity of NSCLC was morphologically estimated on sections immunostained with anti-CD34 antibody.

RESULTS

Eleven of 15 extraneoplastic specimens showed NRP1 expression (73.3%) and 8 showed NRP2 expression (53.3%). The expression level of NRP1 or NRP2 of neoplasmic tissue was higher than that of extraneoplastic tissues (P < 0.01, Mann-Whitney U test). Fifty-five and 44 NSCLCs expressed NRP1 and NRP2, respectively. Forty patients co-expressing NRP1 and NRP2 showed significantly poorer prognosis and increased vessel counts as compared to those 28 cases without co-expression (P < 0.05, log-rank test; P < 0.05, Mann-Whitney U test).

CONCLUSIONS

The co-expression of NRP1 and NRP2 genes is significantly correlated with tumor progression through neovascularization in NSCLC. These results suggest that both NRP1 and NRP2 are key molecules for stromal vascularization by cell-retained VEGF in NSCLC.

Persistence of microscopic human cancers in mice: alterations in the angiogenic balance accompanies loss of tumor dormancy

Some human tumor lines do not form visible tumors when inoculated into immunosuppressed mice. The fate of these human tumor lines was followed by transfecting them with green fluorescence protein before inoculating them into mice. Although the tumor lines failed to grow progressively, they formed small dormant microscopic foci maintained at constant mass by balanced proliferation and apoptosis. Transfecting the cells with either VEGF165 or activated c-Ha-ras induced loss of dormancy, which correlated with a shift in the angiogenic balance toward increased vascularity with reduced tumor cell apoptosis. These results support a model in which loss of dormancy is controlled in part by a switch to an angiogenic phenotype. These tumor lines may serve as models for investigating the cellular mechanisms controlling dormancy and identifying those factors that promote the loss of balanced proliferation and apoptosis. Finally, these models may prove useful in the design and testing of therapies directed toward eradicating dormant tumors and preventing tumor recurrence.

Pathological significance of vascular endothelial growth factor A isoform expression in human cancer

Vascular endothelial growth factor (VEGF) is a highly specific factor for vascular endothelial cells. Five VEGF-A isoforms (splice variants 121, 145, 165, 189 and 206) are generated as a result of alternative splicing from a single VEGF-A gene. These differ in their molecular weights and in biological properties such as their ability to bind to cell-surface heparan sulfate proteoglycans. Deregulated VEGF-A expression contributes to the development of solid tumors by promoting tumor angiogenesis. More specifically, VEGF-A189 expression is related to angiogenesis and prognosis in certain human solid tumors. VEGF-A189 expression is also related to the xenotransplantability of human cancers into immunodeficient mice in vivo. Consequently, inhibition of VEGF-A or VEGF-A189 signaling regulates the development and metastasis of a variety of tumors. This review focuses on recent studies of the mechanisms by which VEGF-A regulates angiogenesis in the cancer stroma and on our recent findings concerning the potential mechanisms of VEGF-A189 expression on tumor growth and metastasis.

Vascular endothelial growth factor (VEGF) expression in the subacromial bursa is increased in patients with impingement syndrome

Vascular endothelial growth factor (VEGF), which is known to be an angiogenetic factor, plays an important role in the inflammation of synovial tissue. To investigate the relationships between VEGF and clinical symptoms in rotator cuff disease, VEGF expression was examined using RT-PCR and immunohistochemical analysis in 50 patients with this disease (26 with full-thickness cuff tear, 12 with partial-thickness tear, and 12 with subacromial bursitis). VEGF mRNA expression was detected in 40 out of 50 patients by RT-PCR. VEGF mRNA expression was found more frequently in the patients with motion pain (39 out of 41) than in those without motion pain (1 out of 9) with statistical significance (Fisher's test, P < 0.001). Thirty-one out of 33 patients with synovial proliferation showed VEGF mRNA expression, whereas the expression of this transcript was found in 9 out of 17 patients without synovial proliferation. This association with synovial proliferation was also significant (Fisher's test, P = 0.0013). Thirty out of 41 patients with motion pain had synovial proliferation but 3 out of 9 patients without motion pain had synovial proliferation. In all these 30 patients with both motion pain and synovial proliferation, VEGF mRNA expression was detected. This association between motion pain and synovial proliferation was also significant (Fisher's test, P < 0.05). The mean vessel count and area in subacromial bursa expressing VEGF was significantly higher than in those without VEGF (Mann Whitney's U test, P < 0.01). These results suggested that VEGF expression is associated with vascularity, synovial proliferation and shoulder motion pain in the rotator cuff disease.

Ribozyme approach to downregulate vascular endothelial growth factor (VEGF) 189 expression in non-small cell lung cancer (NSCLC)

The aim of this study was to further clarify the role of the cell-associated isoform of vascular endothelial growth factor (VEGF189) on tumour growth and vascularity. Five isoforms of VEGF have been identified with different biological activities. VEGF121, VEGF145, VEGF165, VEGF189, VEGF206 are generated by alternative splicing. We used a hammerhead-type ribozyme (V189Rz) to suppress VEGF189 mRNA. The V189Rz specifically cleaved exon 6 of VEGF189 mRNA, but showed no activity against the VEGF121 or VEGF165 isoforms. The V189Rz was introduced into the human non-small cell lung cancer (NSCLC) cell line (OZ-6/VR). The expression level of VEGF189 mRNA was decreased in the OZ-6/VR cells, while VEGF121 and 165 expression was unaltered. The OZ-6/VR cells xenotransplanted into nude mice showed markedly reduced vascularisation and growth, whereas the cell line did not show any decreased growth under tissue culture conditions. The OZ-6/VR cells (1 x 10(5) cells/mouse) formed no tumours, whereas the parental OZ-6 cells formed large tumours within 8 weeks. The specific suppression of VEGF189 by the ribozyme decreased vascularity and xenotransplantability of the lung cancer cell line. Thus, the cell-associated isoform of VEGF, VEGF189, might have a key role in stromal vascularisation and the growth of NSCLC xenografts in vivo.

Cell-retained isoforms of vascular endothelial growth factor (VEGF) are correlated with poor prognosis in osteosarcoma

Vascular endothelial growth factor (VEGF) is a major angiogenic factor. Osteosarcoma is characterised by hypervascularity and metastatic potential. We examined VEGF mRNA expression, VEGF isoform pattern and VEGF receptor (flt-1 and KDR) by RT-PCR analysis in 30 osteosarcomas. All 30 osteosarcomas expressed VEGF mRNA. 17 osteosarcomas (57%) expressed flt-1 mRNA, whilst 20 (67%) expressed KDR mRNA. 6/30 (20%) osteosarcomas were positive for VEGF121 only, 8 (27%) for VEGF121 + VEGF165, and 16 (53%) for VEGF121 + VEGF165 + VEGF189. Patients with osteosarcomas with VEGF165 (n = 24) had significantly poorer prognosis in comparison with those without VEGF165 (P = 0.022, Wilcoxon's test). The osteosarcomas with VEGF165 had significantly increased vascularity assessed on sections immunostained for CD34 (P < 0.001, Mann-Whitney U test). Although VEGF165 is a soluble isoform, it is also retained on the cellular surface. These results suggest that cell-retained VEGF isoforms (VEGF165, VEGF189) might be essential for neovascularisation in osteosarcoma, whilst the soluble VEGF121 isoform is not sufficient to stimulate neovascularisation in this type of neoplasm.

Expression pattern of vascular endothelial growth factor isoform is closely correlated with tumour stage and vascularisation in renal cell carcinoma

Vascular endothelial growth factor (VEGF) has five isoforms (VEGF206, 189, 165, 145 and 121). Increased VEGF expression in renal cell carcinoma (RCC) is associated with angiogenesis, but, it is not apparent which isoform is involved in this effect. We examined the isoform patterns of VEGF by reverse transcription-polymerase chain reaction (RT-PCR) in 47 RCCs. All showed increased VEGF expression as compared with extraneoplastic renal tissue. Four of the 47 RCCs showed VEGF121 alone, 10 showed VEGF121 + 165, and 33 showed the VEGF121 + 165 + 189 pattern. Patients with pathological stage pT3-4 RCC showed the VEGF121 + 165 + 189 isoform pattern at a significantly higher incidence (10/10, 100%) than those with pT0-2 (23/37, 62%) (P < 0.022). The VEGF121 + 165 + 189 isoform pattern was also significantly associated with high vessel counts and density (P = 0.0002, Mann-Whitney U test). These observations suggested that the VEGF189 mRNA isoform is closely associated with angiogenesis and results in the growth of RCC.