Differential effects of the vascular endothelial growth factor receptor inhibitor PTK787/ZK222584 on tumor angiogenesis and tumor lymphangiogenesis.

Halting tumor growth by interfering with tumor-induced angiogenesis is an attractive therapeutic approach. Such treatments include humanized antibodies blocking the activity of vascular endothelial growth factor (VEGF)-A (bevacizumab), soluble VEGF receptor (VEGFR) constructs (VEGF-Trap), or small-molecule inhibitors of VEGFR signaling, including PTK787/ZK222584 (PTK/ZK), sorafenib, and sunitinib. PTK/ZK has been shown previously to specifically block VEGF-induced phosphorylation of VEGFR-1, -2 and -3 and thereby to inhibit endothelial cell proliferation, differentiation, and tumor angiogenesis. We have investigated the effect of PTK/ZK on tumor angiogenesis and tumor lymphangiogenesis using the Rip1Tag2 transgenic mouse model of pancreatic beta cell carcinogenesis. In Rip1Tag2 mice, tumor angiogenesis is predominantly mediated by VEGF-A, and as expected, PTK/ZK efficiently impaired tumor blood vessel angiogenesis and tumor growth. Double-transgenic Rip1Tag2;Rip1VEGF-C and Rip1Tag2;Rip1VEGF-D mice not only exhibit VEGF-A-dependent blood vessel angiogenesis but also tumor lymphangiogenesis induced by the transgenic expression of VEGF-C or -D. In these mouse models, PTK/ZK also repressed tumor blood vessel angiogenesis and tumor growth yet failed to affect tumor lymphangiogenesis and lymphogenic metastasis. Adenoviral delivery of soluble VEGFR-3 also did not prevent tumor lymphangiogenesis in these mice. In contrast, spontaneous tumor lymphangiogenesis, as observed by the stochastic expression of VEGF-C and -D in tumors of neural cell adhesion molecule-deficient Rip1Tag2 mice, was repressed by PTK/ZK and soluble VEGFR-3. The results indicate that the time of onset and the levels of VEGF-C/D expression may be critical variables in efficiently repressing tumor lymphangiogenesis and that pathways other than VEGFR signaling may be involved in tumor lymphangiogenesis.

Loss of neural cell adhesion molecule induces tumor metastasis by up-regulating lymphangiogenesis.

Reduced expression of neural cell adhesion molecule (NCAM) has been implicated in the progression to tumor malignancy in cancer patients. Previously, we have shown that the loss of NCAM function causes the formation of lymph node metastasis in a transgenic mouse model of pancreatic beta cell carcinogenesis (Rip1Tag2). Here we show that tumors of NCAM-deficient Rip1Tag2 transgenic mice exhibit up-regulated expression of the lymphangiogenic factors vascular endothelial growth factor (VEGF)-C and -D (17% in wild-type versus 60% in NCAM-deficient Rip1Tag2 mice) and, with it, increased lymphangiogenesis (0% in wild-type versus 19% in NCAM-deficient Rip1Tag2 mice). Repression of VEGF-C and -D function by adenoviral expression of a soluble form of their cognate receptor, VEGF receptor-3, results in reduced tumor lymphangiogenesis (56% versus 28% in control versus treated mice) and lymph node metastasis (36% versus 8% in control versus treated mice). The results indicate that the loss of NCAM function causes lymph node metastasis via VEGF-C- and VEGF-D-mediated lymphangiogenesis. These results also establish Rip1Tag2;NCAM-deficient mice as a unique model for stochastic, endogenous tumor lymphangiogenesis and lymph node metastasis in immunocompetent mice.

Novel technologies and recent advances in metastasis research.

In this review we have attempted to summarize some of the recent developments in using novel technologies to unravel the molecular mechanisms of tumor progression, in particular the formation of tumor metastasis. In order to push forward the frontiers in cancer research, it is obvious that several fields have to be further developed and interconnected: (1) clinical, epidemiological and pathological studies which mainly use innovative technologies, including microarray technology and nanotechnology to determine as many parameters as possible, (2) the development of improved and suitable bioassays and better animal models and (3) the use of novel computation and bioinformatics methods to sample and integrate the exponentially growing sets of data coming from such investigations. Fashionable as scientists are, this new endeavor may be called systems biology.

Alterations in CDKN2A locus as potential indicator of melanoma predisposition in relatives of non-familial melanoma cases.

AIM: To examine constitutional alterations of CDKN2A/p16INK4A locus as a potential indicator of melanoma predisposition among the first-degree relatives of patients with malignant melanoma. METHOD: The study included eight families with a single member affected with melanoma. Members of the families were screened for allelic cosegregation with 9p21 region polymorphic markers IFNA, D9S126, and D9S104. The patient's tumors were screened for loss of heterozygosity (LOH) with the same markers, as well as for single strand conformational polymorphism (SSCP) variability of CDKN2A. In suspect cases, constitutional DNA was examined by SSCP and direct sequencing. RESULTS: LOH was detected in four cases, and SSCP indicated variability in at least one CDKN2A exon in these tumor samples. In three of four LOH cases, the remaining allele cosegregated within the family, which was interpreted as a preliminary indicator of potential genetic predisposition. In one of these three families, we found constitutional CDKN2A mutations in the patient and one of the relatives. In the second family, only the patient had the constitutionally altered gene, whereas no constitutional CDKN2A alterations were detected in the third family. All significant mutations were different and had not been reported before. CONCLUSION: We detected one case of melanoma predisposition among unaffected family members, which corresponded to statistical expectations for such a small number of screened families. Since constitutional mutations of CDKN2A exons have limited incidence, our stepwise approach seemed to be more informative and more affordable than straightforward CDKN2A sequencing of all subjects.

Variable expression of Gorlin syndrome may reflect complexity of the signalling pathway.

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) or Gorlin syndrome is an autosomal dominant disorder characterized by cancer predisposition and multiple developmental defects. Syndrome related disorders have been attributed to alterations of PTCH gene, which plays an important role in Shh signalling pathway. Unresolved complexities of the pathway impede understanding of mechanisms through which PTCH alterations lead to variable phenotype expression in Gorlin syndrome patients, while the role of chromosomal instability is not yet clear. To increase our understanding of NBCCS, every manifestation of the syndrome and associated genetic damage should be seriously considered. Therefore, several atypical NBCCS cases are presented in this paper.