Molecular and cellular mechanisms of lymphangiogenesis.

Lymphangiogenesis is the growth and formation of new lymphatic vessels. It occurs in normally developing tissues and in pathological processes like inflammation, wound healing, lymphoedema and in cancer. New molecular markers that are specific to the lymphatic endothelium include: podoplanin, prox-1 and LYVE-1. The molecular mechanisms of lymphangiogenesis are not clear, but vascular endothelial growth factors (VEGF-C and VEGF-D) within tumours may simulate endothelial cells within tumour tissues to grow and generate new lymphatics. We report the current knowledge of molecular and cellular mechanisms of lymphangiogenesis.

Interleukin 7 upregulates vascular endothelial growth factor D in breast cancer cells and induces lymphangiogenesis in vivo.

BACKGROUND: Interleukin (IL) 7 is known to stimulate growth of breast cancer cells in vitro. It has been recently associated with node-positive tumours and with poor survival in breast cancer. The effects of IL-7 on the lymphangiogenic properties of breast cancer cells were explored. METHODS: The effects of IL-7 on the expression of vascular endothelial growth factors (VEGFs) in MDA MB-231, MCF-7 and BT-483 cells were analysed by reverse transcriptase-polymerase chain reaction and western blotting. An in vivo lymphangiogenesis model using nude mice was developed. The newly generated microtubules were stained with anti-von Willebrand factor and anti-LYVE-1 (lymphatic vessel endothelial hyaluronan receptor) antibodies. RESULTS: All VEGFs (VEGF-A, -B, -C and -D) were expressed in breast cancer cells, but at different levels. IL-7 increased the expression of VEGF-D at both mRNA and protein levels in MCF-7 and MDA MB-231 cells. In the in vivo model, IL-7 significantly induced the formation of lymphatic LYVE-1-positive, but not vascular von Willebrand factor-positive, microtubules (P = 0.021 versus sections without IL-7). CONCLUSION: IL-7 induced the lymphangiogenic properties of breast cancer cells, probably by upregulation of VEGF-D. This might have a significant impact on the lymphatic spread of breast cancer.

Lymphangiogenesis and its role in cancer.

In many tumour types, lymphatic vasculature serves as a major route for tumour metastasis. The dissemination of malignant cells to the regional lymph nodes is an early step in the progression of many solid tumours and is an important determinant of prognosis. Lymphangiogenesis (formation of new lymphatic vessels) is thought to be crucial for cancer cells to metastasise to the regional lymph nodes. However research in this important process has been neglected largely due to the lack of molecular markers specific to the lymphatic endothelium. Recently, several specific markers have been identified including LYVE-1, podoplanin and prox-1. Although the biology of lymphangiogeneis, particularly its regulation, is still far from clear, it is now well established that tumours are lymphangiogenic i.e. they could induce the generation of their own lymphatics and metastasise to the regional lymph nodes. It is thought that the interruption of the main signalling pathways involved in this process could help to prevent lymphatic spread of many tumours. Furthermore, understanding the molecular mechanisms in lymphangiogenesis might help to develop new therapeutic strategies against cancer lymphatic spread. Here, we reviewed the literature in regards to the biology of lymphangiogenesis, its molecular regulation, lymphatic markers and the significance in human solid tumours.

Aberrant expression of interleukin-7 (IL-7) and its signalling complex in human breast cancer.

Interleukin-7 (IL-7), a haematopoietic growth factor, is known to induce the differentiation and proliferation of some haematological malignancies including certain types of leukaemias and lymphomas. However, little is known about its role in solid tumours, including breast cancer. In this study, the expression level of IL-7, IL-7 receptor (IL-7R) and their downstream signalling molecules, including the Janus kinases (Jak-1 and Jak-3), phosphoinositide 3-kinase (PI3-K) and signal transducers and activators of transcription (Stat-5) were analysed using the reverse transcriptase-polymerase chain reaction (RT-PCR), real-time quantitative PCR and immunohistochemistry in a cohort of patients with breast cancer. The results were analysed in relation to tumour grade, TNM stage, patients' prognosis (using the Nottingham Prognostic Index (NPI)) and survival. The levels of expression of IL-7, IL-7R, Jak-1, Jak-3, PI3-K and Stat-5 were significantly higher in the most aggressive tumours. With the exception of Stat-5 expression, the transcript copies of IL-7 and all other signalling molecules were higher in patients with the worst prognoses (NPI3) and in patients who died from breast cancer after 72 months of follow-up. This aberrant expression of IL-7 and its signalling intermediates in invasive breast cancers could have significant diagnostic and prognostic implications. Measuring these molecules in breast cancer tissues may provide, for the first time, important molecular indicators of tumour differentiation, aggressiveness, nodal status, prognosis and patient survival.

Interleukin 7 induces the growth of breast cancer cells through a wortmannin-sensitive pathway.

BACKGROUND: Interleukin (IL) 7 is a growth factor able to induce the growth and development of certain haematopoietic malignancies including lymphoma and leukaemia. Its effects on solid tumours, including breast cancer, are unknown. This report concerns the effect of IL-7 on the growth of breast cancer cells. METHODS: Reverse transcription-polymerase chain reaction, western blotting and immunoprecipitation were used to detect to detect IL-7 and its receptor (IL-7R) in breast cancer cell lines MDA MB-231 and MCF-7. These cells were treated with various concentrations of human recombinant IL-7 over specified intervals. Changes in growth were assessed using colorimetric and fluorescence-based technologies. Selective IL-7 downstream signalling inhibitors (wortmannin, JAK-3 inhibitor 1, piceatanol and AG 490) were use to clarify the pathways through which IL-7 may affect breast cancer growth. RESULTS: IL-7 significantly accelerated the growth of MDA MB-231 cells and MCF-7 cells (P = 0.004 and P = 0.012, respectively, in PicoGreenassay). The maximum effects were observed after incubation for 72 h. The stimulatory effect of IL-7 on cell growth was completely eliminated in the presence of wortmannin (P = 0.001 and P = 0.003 versus no inhibitor in MDA MB-231 and MCF-7 cells, respectively) and JAK-3 inhibitor 1 (P < 0.001 versus no inhibitor in both cell lines), but not in the presence of piceatanol and AG 490. CONCLUSION: IL-7 induced the growth of breast cancer cells in vitro through a wortmannin-sensitive pathway. This may have an important impact on research into breast cancer development and progression.

Interleukin-7 (IL-7) and IL-7 receptor (IL-7R) signalling complex in human solid tumours.

Interleukin-7 (IL-7) plays an important role in the normal development and maintenance of the human immune system. Its effects are mediated via its receptor, IL-7R. Ligand-receptor engagement results in a cascade of phosphorylation events mediated by various molecules including the Janus kinases (Jak1 and Jak3), PI3-kinase, Stats (signal transducers and activators of transcription) and other molecules. The activation of IL-7 signalling pathway results in survival, proliferation, differentiation and maturation of haematopoietic cells including B and T lymphocytes. Although the relationship of IL-7 with the development and differentiation of some haematological cancers like leukaemias and lymphomas is well recognised, little is known about it involvement with solid tumours. There are several studies that have revealed IL-7/IL-7R expression in epithelial systems and some human solid epithelial tumours. Furthermore, IL-7 can be produced by some human tumour cells and involved in tumour development and progression. In this review article we have summarised the main biological activities of IL-7 and its downstream signalling complex in relation to some human solid malignancies.