The metastatic phenotype--prognostic implications

Ultraviolet A exposure alters adhesive properties of mouse melanoma cells

BACKGROUND

We have examined whether ultraviolet A (UVA) irradiation could alter adhesive properties of melanoma cells. As an experimental in vitro model, we have used C57BL/6 mouse-derived B16- F1 and B16-F10 melanoma cell lines and the syngeneic MS-1 endothelial cell line.

METHOD/RESULT

The melanoma cells were exposed to different doses of UVA irradiation. We have determined that a single dose of UVA at 8 and 12 J/cm(2) causes an 88% (P<0.001) and a 32% (P<0.05) increase in B16-F1 melanoma cell adhesiveness to the non-irradiated endothelial monolayer, respectively. The peak of the response was 24 h after the irradiation. The UVA dose of 8 J/cm(2) delivered in four doses separated by 1 h intervals (4 x 2 J/cm(2)) had led to a caused 149% (P<0.001) increase of B16-F1 melanoma adhesiveness already at 1 h after the last dose of UVA. Besides the induction of increase in the melanoma-endothelial cell adhesion, UVA exposure has induced a rapid decline (1 h after exposure) in homotypic melanoma-melanoma cell adhesion (clustering). The clustering decline of B16-F1 cells with a single dose of UVA at 8 J/cm(2) was by 61% (P<0.05) and by 35% (P<0.05) with 4 x 2 J/cm(2). Pilot experiments have shown that the changes of the adhesive properties of melanoma cells were accompanied by an increase in N-cadherin expression and a decline in E-cadherin expression. Such a change in cadherin expression profile has been shown to be an indicator of the increased metastatic potential.

CONCLUSION

Our results suggest that UVA radiation appears to alter the adhesive properties of melanoma cells in vitro, by diminishing the melanoma-melanoma adhesion and by increasing melanoma adhesion to the endothelium. This suggests that UVA exposure might increase the metastatic capability of the melanoma cells.

Preparation and characterization of monoclonal antibody against protein tyrosine phosphatase PRL-3

PRL-3 is a newly identified nonclassical protein tyrosine phosphatase associated with colorectal cancer metastasis. To prepare specific monoclonal antibody (MAb) against PRL-3, cDNAs of PRL-1, -2, and -3 were cloned by RT-PCR and inserted into prokaryotic expression vector pGEX-4T1, respectively. The fusion proteins were expressed in Escherichia coli. Monoclonal antibody against PRL-3 was obtained with hybridoma technique and specific ELISA screening. Western blotting and immunohistochemistry assays showed that MAb 3B6 had specific binding ability with PRL-3 protein in eukaryotic cells. This MAb will be a helpful tool for the detection of PRL-3 protein in the tissues and serum of colorectal cancer and other cancer patients.

The association of the expression level of protein tyrosine phosphatase PRL-3 protein with liver metastasis and prognosis of patients with colorectal cancer

PURPOSE

To investigate PRL-3 protein expression in normal colorectal epithelia and colorectal cancers with monoclonal antibody (MAb) against PRL-3.

METHODS

MAb against PRL-3 was prepared with the hybridoma technique, and its specificity was confirmed with ELISA and Western blotting assays. The expression of PRL-3 protein in normal colorectal epithelia and colorectal cancers was examined by immunohistochemistry assay. Logistic regression and survival analysis were performed to determine the clinical significance of PRL-3 expression.

RESULTS

MAb 3B6 against PRL-3 was obtained and showed high specificity. PRL-3 protein was expressed in two of 28 (7.1%) normal colorectal epithelia, 21 of 88 (23.9%) primary colorectal cancers, 22 of 41 (53.7%) metastatic lymph nodes and eight of 12 (66.7%) liver metastases, respectively. The PRL-3 expression rates of metastases were significantly higher than those of primary colorectal cancers and normal colorectal epithelia (P < 0.05). PRL-3 expression was significantly associated with the liver metastasis of colorectal cancer (P = 0.004) and tended to shorten survival time (P = 0.0145).

CONCLUSIONS

This is the first study demonstrating that PRL-3 is a potential marker for liver metastasis of colorectal cancer and negatively influences the prognosis of colorectal cancer patients.

Can axillary dissection be avoided by improved molecular biological diagnosis?

Axillary dissection is presently a routine staging procedure in the management of breast cancer. The use of adjuvant systemic treatment is largely based on the diagnosis of axillary metastases. Routine axillary dissection leads to acute and chronic side-effects in a large proportion of patients. The sentinel node technique is presently explored with the aim of decreasing the need for standard axillary dissection. A complementary way forward is to analyse the primary breast cancer for molecular markers with prognostic significance with reference to the risk for metastatic capacity and thereby obtain a 'biological staging' and identify those patients in need of systemic adjuvant therapy. A large number of molecular biological factors have been shown to have prognostic significance in breast cancer e.g. c-erbB-2, p53, uPA, PAI-I and VEGF. This article reviews the expression of these and other factors in the primary breast cancers in relation to the risk for axillary and systemic metastatic disease, with the long-term aim of excluding routine axillary dissection.

ERK signalling in metastatic human MDA-MB-231 breast carcinoma cells is adapted to obtain high urokinase expression and rapid cell proliferation

Increased urokinase plasminogen activator (u-PA) production is associated with tumor invasion and metastasis in several malignancies, including breast cancer. The mechanisms underlying constitutive u-PA expression are not well understood. We examined the relationship between the signal strength of the ERK pathway and the level of u-PA expression in the metastatic human breast cancer cell line MDA-MB-231. Treatment with the MEK1 inhibitor PD98059 resulted in decreased ERK1/2 phosphorylation and decreased u-PA mRNA and protein expression. Inhibition of ERK1/2 activity also led to decreased cell proliferation and to decreased cyclin D1 expression. Less than 5% of total ERK1/2 was phosphorylated in exponentially growing MDA-MB-231 cells, and ERK1/2 activity could be stimulated by okadaic acid. Okadaic acid did not stimulate u-PA expression, but induced strong expression of the cdk-inhibitor p21Cip1. These findings suggest that ERK1/2 signaling is tuned to a level which results in high u-PA expression and rapid cell proliferation.

Late peritoneal metastasis in a patient with osteosarcoma

A 19-year-old man with a high-grade osteosarcoma of the femur, treated with neoadjuvant chemotherapy, surgery, and adjuvant chemotherapy suffered from lung metastases 15 months after diagnosis. They were resected. Thirteen months later, he had vague abdominal complaints which, after analysis, proved to be caused by peritoneal metastasis. A review of the literature, possible physiopathological mechanisms of increased occurrence of unusual metastases and the role of bone scintigraphy in the follow-up of patients with osteosarcoma are discussed.

Increased expression of alpha-enolase in c-jun transformed rat fibroblasts without increased activation of plasminogen

Two-dimensional gel electrophoresis was used to identify polypeptides differentially expressed between normal and c-jun transformed rat fibroblasts. The level of a 49 kDa polypeptide was 3-fold elevated in c-jun transformed cells. Sequence analysis by ion trap mass spectrometry identified the polypeptide as rat alpha-enolase. Enolase functions as a cell surface receptor for plasminogen, suggesting that upregulation may increase plasminogen activation and cell surface proteolysis important for tumor growth. However, no difference was observed between normal and transformed cells in formation of plasmin, suggesting that upregulation of alpha-enolase may contribute to an increased metabolic capacity, but not to increased plasminogen activation.