Suppression of angiogenesis and tumour progression by combretastatin and derivatives.

The search for small molecule inhibitors has gained prominence with the recognition of their inherent advantage for cancer therapy. Combretastatin is a naturally occurring small stilbenoid. By virtue of the ability to bind to tubulin combretastatin and its derivatives promote depolymerisation of microtubules as well as inhibit tubulin polymerisation. This suppresses cell proliferation signalling and induces apoptosis. Combretastatins activate mitotic checkpoints that lead to mitotic catastrophe and apoptosis. They subvert the signalling systems which stimulate invasion, activate EMT (epithelial mesenchyme transition) and promote tumour progression. Allied with the ability to suppress angiogenesis these compounds have been viewed as potential inhibitors of metastasis. The notion of merging RTK (receptor tyrosine kinase) inhibition with suppression of invasion and possible inhibition of EMT has contributed to the credibility of combretastatins as anti-cancer agents. Invaluable are their attributes of inhibiting tumour growth and induction of apoptosis and necrosis by reducing blood supply to the tumour. Aside from these biological effects, this commentary also discusses the issues of the targeting of combretastatins to the tumour vasculature and effective delivery of the drugs encapsulated in nanospheres. Notwithstanding the perceived benefits, one can see a compelling need to understand the effects of combretastatin on the actin cytoskeletal dynamics and the disruption of microtubule polymerisation, and whether it is more efficient a tumour inhibitor than the conventional drugs that target microtubule dynamics. Combinations of combretastatins with other vascular disrupting agents have been attempted. It is essential to establish the perceived inhibition of EMT beyond reasonable doubt. This might justify using the combretastatins with allosteric EMT and Akt inhibitors as additional choices for pre-clinical/clinical studies.

Therapeutic approach to the management of HER2-positive breast cancer metastatic to the brain.

HER2 positive breast cancers have been shown to have a greater propensity to metastasise to the brain. This may be due to several reasons, including the creation of a "sanctuary-site" for tumour in the brain following trastuzumab therapy. Elucidating the mechanism of this phenomenon may aid the prevention or intervention and treatment of such metastases, but research is limited by the deficiency and diminished access of CNS tissue. However, CNS penetrable HER2 receptor antagonists such as lapatinib and intrathecal administration of trastuzumab might benefit patients, and are worthy of further investigation. New avenues of molecular approach have focused on manipulating signal transduction system involved in HER2 function. The importance of systemic therapies and those targeted to metastatic lesions is emphasised and evaluated here.

Metastasis promoter S100A4 is a potentially valuable molecular target for cancer therapy.

The growth, invasion and metastatic spread of cancer have been identified with the deregulation of cell proliferation, altered intercellular and cell-substratum adhesion and enhanced motility and the deposition of disseminated cancer cells at distant sites. The identification of therapeutic targets for cancer is crucial to human welfare. Drug development, molecular modelling and design of effective drugs greatly depend upon the identification of suitable therapeutic targets. Several genetic determinants relating to proliferation and growth, invasion and metastasis have been identified. S100A4 appears to be able to activate and integrate pathways to generate the phenotypic responses that are characteristic of cancer. S100A4 signalling can focus on factors associated with normal and aberrant proliferation, apoptosis and growth, and differentiation. It is able to activate signalling pathways leading to the remodelling of the cell membrane and the extracellular matrix; modulation of cytoskeletal dynamics, acquisition of invasiveness and induction of angiogenesis. Therefore S100A4 is arguably a molecular target of considerable potential possessing a wide ranging biological activity that can alter and regulate the major phenotypic features of cancer. The evolution of an appropriate strategy that permits the identification of therapeutic targets most likely to be effective in the disease process without unduly affecting normal biological processes and function is an incontrovertible imperative. By virtue of its ability to activate interacting and multi-functional signalling systems, S100A4 appears to offer suitable targets for developing new therapeutic procedures. Some effectors of the S100A4-activated pathways might also lend themselves as foci of therapeutic interest.

Metastasis Promoter S100A4 is a Potential Molecular Therapeutic Target.

S100A4, a member of the S100 family of proteins involved in calcium signalling, has come into the fore in recent years on account of its close relationship with tumour development and progression; therefore, S100A4 commends itself as a prime therapeutic target. The phenotypic effects of S100A4 are generated via diverse signalling pathways encompassing and incorporating the functions of cell cycle regulators, growth factor receptors, extracellular matrix components, and the inducers of angiogenesis and lymphangiogenesis. By virtue of this, S100A4 signalling can be specifically targeted to down-regulate the phenotypic activities that contribute to the growth, invasion and metastasis of cancer. Here, the discussion has focused on the signalling pathways that S100A4 uses, with a view to identifying the most effective targets to which drugs can be designed and specifically directed. Some approaches to the problem of inhibiting or deregulating the functions of S100A4, to control invasion and metastasis have been identified. S100A4 could provide a wide channel to control the growth, invasion and secondary spread of cancer and, thus, amply rationalise and validate it as an important therapeutic target.

Hormonal influences on cancer progression and prognosis.

Cell differentiation, proliferation, apoptosis, and cell motility are induced and regulated by a host of growth factors, vitamins, and hormones. The mode of function of these modifiers of biological response, the signaling pathways that they activate, and the interacting pathways that can influence the biological outcome have been the focus of attention. Especially recognized and discussed in this review is the deregulation of their function, leading to abnormalities in cell proliferation, alteration of intercellular adhesive cohesion, remodeling of the extracellular matrix, and invasive behavior and metastatic deposition that are so characteristic of tumor development and progression, which strongly underscores the concept of molecular progression of cancer constructed on the basis of the relationship between genetic changes and the biological events associated with cancer progression. The molecular changes associated with hormone- and vitamin-driven responses and the deregulation of the expression and function of their target genes seem to correlate with specific biological events linked with cancer invasion and progression, and these findings could lead to the establishment of new markers of progression and to the development of new strategies for patient management. The scope of this work has been restricted by design and is dictated by the field of interest of the author's laboratory, but it is hoped that this field would be regarded adequately to reflect the wide genre of scientific interest in this field of human disease.

Stathmin in Cell Proliferation and Cancer Progression.

The phosphoprotein stathmin exerts profound influences on cell proliferation, differentiation and in cell motility. These phenotypic features are displayed in response to specific signals imparted to the cell by biological response modifiers. Stathmin functions as a focal point in co-ordinating and directing the cellular signals into specific and defined pathways. Two biological features that characterise cancer are the deregulation of cell proliferation leading to tumour growth and invasive behaviour. Stathmin is up-regulated in many neoplasms and the modulation of its expression correlates with invasion and metastasis and highly proliferating normal tissues. The integrity of the transduction of extracellular signals is essential for the normal functioning of the cellular machinery in cell differentiation, morphogenesis and cell proliferation, apoptosis, growth and senescence. Stathmin mediates these pathways of signalling. Stathmin has been implicated in both G1-S and G2-M checkpoint control of cell cycle progression by influencing the dynamics of microtubule formation and progression of the cell cycle. Stathmin appears to exert its regulatory effects at both G1-S and G2-M checkpoints by interacting with other cell cycle control proteins such as p53 and rb and with cancer metastasis promoting or inhibiting genes as well as other proteins such as heat shock proteins. Stathmin co-ordinates the signalling by extracellular matrix proteins, and defines intercellular adhesion and cell motility. Therefore, the deregulation of stathmin function would have profound implications in the pathogenesis and progression of cancer.

Prediction of nodal spread of breast cancer by using artificial neural network-based analyses of S100A4, nm23 and steroid receptor expression.

The expression of tumour promoter gene S100A4, metastasis suppressor gene nm23, oestrogen and progesterone receptors, and tumour grade and size have been investigated for their potential to predict breast cancer progression. The molecular and cellular data have been analysed using artificial neural networks to determine the potential of these markers to predict the presence of metastatic tumour in the regional lymph nodes. This study shows that tumour grade and size are poor predictors. The relative expression of S100A4 and nm23 genes is the single most effective predictor of nodal status. Inclusion of oestrogen- and progesterone-receptor status with tumour grade and size markers improves prediction; however, there may be some overlap between steroid receptors and molecular markers. This study also underscores the power of artificial neural network techniques to predict the potential of primary breast cancers to spread to axillary lymph nodes. This could aid the clinician in determining whether invasive procedures of axially node dissection can be obviated and whether conservative forms of treatment might be appropriate in the management of the patient.

Oestrogen and progesterone receptor expression influences DNA ploidy and the proliferation potential of breast cancer cells.

The influence of oestrogen (ER) and progesterone (PgR) receptor has not been investigated in relation to DNA ploidy and cell proliferation. Here we have investigated a series of 46 breast cancer fine-needle aspirates in order to define the prognostic value of ER/PgR and possible correlations between DNA ploidy, size of the S-phase fraction (SPF) and cell cycle distribution features measured by image cytometry (ICM) and ER/PgR status of the primary tumours. The breast cancers were grouped into ER+/PgR+, ER+/PgR- and ER-/PgR-. Inter-group comparisons were made of DNA ploidy, SPF and the pattern of cell cycle distribution defined by the G0G1/G2M ratio in order to determine the influence of ER and PgR expression on the respective cell features. Our studies suggest that ER and PgR exert differential effects on the cell features examined. This study also analysed the possibility of predicting nodal involvement and 5-year disease-free survival by combining ER/PgR status with DNA ploidy, SPF and G0G1/G2M ratios. A high degree of accuracy was achieved for predicting both nodal involvement and 5-year disease-free survival. These findings suggest that a combination of ER/PgR status with DNA ploidy, SPF and cell cycle distribution provide a powerful marker for disease prognosis.

Differential regulation of Notch signal transduction in leukaemia and lymphoma cells in culture.

The transduction of Notch signal plays an intricate role in cell differentiation and pathogenesis of haematological malignancies as well as in certain congenital conditions. We found no genomic changes in either gene in 34 leukaemic samples and 25 leukaemia and lymphoma cell lines. The functionality of Notch signalling was tested using HES1 gene activation. We show that Notch signalling is differentially regulated in T-acute lymphoblastic leukaemia (ALL) and B-lymphoma cells. The Notch pathway is intact in a majority of B-lymphoma cell lines, but EBNA2, which mimics notch function, can occasionally activate the pathway. In contrast, the Notch pathway is constitutively active in T-ALL. This is the first demonstration of a distinction between B-lymphomas and T-cell leukaemias in the functioning of the Notch-signalling pathway. This might be related to their pathogenesis.

Assessment of nodal involvement and survival analysis in breast cancer patients using image cytometric data: statistical, neural network and fuzzy approaches.

Accurate and reliable decision making in breast cancer prognosis can help in the planning of suitable surgery and therapy and, generally, optimise patient management through the different stages of the disease. In recent years, several prognostic factors have been used as indicators of disease progression in breast cancer. In this paper we investigate a fuzzy method, namely fuzzy k-nearest neighbour technique for breast cancer prognosis, and for determining the significance of prognostic markers and subsets of the markers, which include histology type, tumour grade, DNA ploidy, S-phase fraction, G0G1/G2M ratio, and minimum (start) and maximum (end) nuclear pleomorphism indices. We also compare the method with (a) logistic regression as a statistical method, and (b) multilayer feed forward backpropagation neural networks as an artificial neural network tool, the latter two techniques having been widely used for cancer prognosis. Nodal involvement and survival analyses in breast cancer are carried out for 100 women who were clinically diagnosed with breast disease in the form of carcinoma and benign conditions, and seven prognostic markers collected for each patient. For nodal involvement analysis, node positive and negative patients are predicted whereas survival analysis is carried out for two categories: whether a patient is alive or dead within 5 years of diagnosis. The results obtained show that the fuzzy method yields the highest predictive accuracy of 88% for both nodal involvement and survival analyses obtained from the subsets of [tumour grade, S-phase fraction, minimum (start) nuclear pleomorphism index] and [tumour histology type, DNA ploidy, S-phase fraction, G0G1/G2M ratio], respectively. We believe that this technique has produced more reliable prognostic factor models than those obtained using either the statistical or artificial neural networks-based methods.

Notch signal transduction is not regulated by SEL1L in leukaemia and lymphoma cells in culture.

The transduction of Notch signal plays an intricate role in cell differentiation and pathogenesis of haematological malignancies as well as in certain congenital conditions. The functionality of Notch signalling was tested using HES1 gene activation. SEL1 gene product has been postulated to be a negative regulator of Notch signalling. We investigated the relationship between Notch signalling and the expression of SEL1L gene in a number of leukaemia and lymphoma cells in culture. The cell lines could be separated into two groups. Group 1 contained lymphoma cell lines in which Notch signalling was intact; of these 4 cell lines were SEL1L+/HES1- and 3 SEL1L-/HES1-. Notch signalling was not subverted by EBNA2 expression in these lymphoma cells. In Group 2 cell lines Notch signalling was constitutively active but 6 out of 7 cell lines expressed SEL1L at high levels. In summary, a majority of cell lines of both groups express SEL1L and no inverse relationship is evident between SEL1L expression and the status of Notch signalling. The present investigation therefore suggests that SEL1L may not exert a negative regulatory influence on Notch signalling. No genomic alterations affecting SEL1L were detected either in the lymphoma or T-ALL cell lines tested. Taken together the present findings do not support the postulated negative regulatory role for SEL1L in Notch signalling.

Oxidative stress signalling in the apoptosis of Jurkat T-lymphocytes.

The pathways of transduction of oxidative stress signals have been studied using the Jurkat T cell model. The oxidative stress was induced by exposure of the cells to 100 microM H(2)O(2). DNA damage was detected within 15 min after commencement of treatment. DNA damage repair occurred within about 1 h in cells exposed to oxidative stress for 15 min. In continuous exposure to stress, DNA repair was slower and control levels of DNA integrity were not reached. DNA repair did not involve gene transcription. H(2)O(2) at 100 microM caused cell death by necrosis as well as by apoptosis. Both these processes were induced by 15 min exposure to the stress stimulus. However, some important differences were found between necrosis and apoptosis. Necrosis was more rapid, began within an hour of treatment and continued to increase during the full duration of the experiment. But apoptosis was seen after 4 h from treatment and was conspicuous between 6 and 20 h after the start of treatment. The necrotic phase preceded apoptosis, although these did show an overlap. In the necrotic phase, Bcl-2, Caspase 8 genes were down regulated. The 6-20 h phase characterised by a marked increase in apoptosis is accompanied by the up regulation of both Bcl-2 and Caspase genes. Expression of the Fas and p53 genes was not altered in either phase. We also analysed the levels of expression of the scavenging genes whose gene products are involved in detoxification. No modulation of the antioxidant enzymes, catalase, Cu/Zn superoxide dismutase and glutathione peroxidase was detectable.

DNA ploidy and cell cycle distribution of breast cancer aspirate cells measured by image cytometry and analyzed by artificial neural networks for their prognostic significance.

Chromosomal abnormalities are commonly associated with cancer, and their importance in the pathogenesis of the disease has been well recognized. Also recognized in recent years is the possibility that, together with chromosomal abnormalities, DNA ploidy of breast cancer aspirate cells, measured by image cytometric techniques, may correlate with prognosis of the disease. Here, we have examined the use of an artificial neural network to predict: 1) subclinical metastatic disease in the regional lymph nodes and 2) histological assessment, through the analysis of data obtained by image cytometric techniques of fine needle aspirates of breast tumors. The cellular features considered were: 1) DNA ploidy measured in terms of nuclear DNA content as well as by cell cycle distribution; 2) size of the S-phase fraction; and 3) nuclear pleomorphism. A further objective of the study was to analyze individual markers in terms of impact significance on predicting outcome in both cases. DNA ploidy, indicated by cell cycle distribution, was found markedly to influence the prediction of nodal spread of breast cancer, and nuclear pleomorphism to a lesser degree. Furthermore, a comparison between histological assessment and artificial neural network prediction shows a closer correlation between the neural approach and the development of further metastases as indicated in subsequent follow-up, than does histological assessment. These data demonstrate that artificial neural networks are capable of providing powerful and reliable indicators of possible lymph node metastasis, using measurements of cellular features alone.

Stathmin is involved in S100A4-mediated regulation of cell cycle progression.

S100A4 is a cell proliferation- and cancer metastasis-related gene. Previous studies have shown that over-expression of S100A4 drives the cells into the S-phase of the cell cycle, with concomitant enhancement of p53 detection. This has led to the postulate that S100A4 could be controlling cell cycle progression by sequestering p53 and abrogating its G1-S checkpoint control. Cells induced by S100A4 to enter the S-phase do successfully negotiate the G2-M checkpoint control. Here we show that S100A4 is also involved in the regulation of control at this checkpoint. Stathmin is known to be associated, together with p53 in controlling G2-M transition. We present evidence that the expression of S100A4 and stathmin genes is up regulated in exponentially growing HeLa cells. They are down regulated in parallel when cell proliferation is inhibited by hyperthermia and 4-hydroxynonenal (4-HNE). We postulate that S100A4 might directly induce stathmin up regulation to enable cells to enter into mitosis. Since wild-type p53 is known to down regulate stathmin expression, we further postulate this might also involve S100A4-mediated sequestration of p53. The expression of heme oxygenase (HO-1), a stress-response protein, has been used to monitor effects of hyperthermia, 12-O-tetradecanoly phorbol 13-acetate (TPA) and 4-HNE. All these treatments induced HO-1 and also when cells growing in serum-deficiency were restored with full serum. HO-1 induction occurred irrespective of S100A4 expression status. HO-1 gene has responsive elements for many angiogenic agents and induces marked neovascularisation of tumours. We suggest therefore that S100A4 may not possess angiogenic properties.

S100A4 (MTS1) calcium binding protein in cancer growth, invasion and metastasis.

The S100 family of calcium binding proteins has been shown to be involved in a variety of physiological function, such as cell proliferation, extracellular signal transduction, intercellular adhesion, motility as well as cancer metastasis. The role played by a member of the S100 gene family, viz. S100A4 (also referred to as mtsl, 18A2/mtsl, pEL-98, p9Ka, metastasin) in the control of cell proliferation as well as in cancer invasion and metastasis has now been extensively studied in a number of laboratories. The protein encoded by S100A4 gene is now known to be capable of regulating cell cycle progression, modulating intercellular adhesion and invasive and metastatic properties of cancer cells. The S100A4 protein appears to be able to sequester and disable the p53 suppressor protein which controls G1-S transition of cells as well as the exit of cells from the S phase into mitosis G2-M transition is believed to involve the induction of stathmin (Op18) gene expression. The expression of this gene has been found to parallel that of S100A4, S100A4 also appears to take part in the homeostasis of growth, with apparent involvement also in growth factor signal transduction and apoptotic cell death. There is considerable evidence that S100A4 expression alters the adhesive properties of cells, possibly by remodelling the extracellular matrix and promoting a redeployment of adhesion-mediating macromolecules occurring in the extracellular matrix. Using transfection technology, it has been shown that over-expression of S100A4 enhances lung colonisation by cancer cells. The transfection and expression of antisense constructs, in contrast, inhibit metastatic localisation in the lung. S100 proteins levels in serum and in tumour tissue are increasingly being monitored and have been regarded as good indicators of the state of cancer progression. Valuable evidence has accumulated regarding the expression of S100A4 in human melanomas. In carcinoma of the breast, the level of expression of S100A4 has been found to be closely related to metastatic spread of the cancer to regional lymph nodes. The purpose of this review is to emphasise the need to focus sharply upon the mechanisms by which S100 proteins in general and S100A4 in particular subserve the wide variety of functions currently attributable to them.

Analysis of image cytometry data of fine needle aspirated cells of breast cancer patients: a comparison between logistic regression and artificial neural networks.

Image flow cytometry data of aspirated tumour cells from 102 patients with breast cancer were analysed and used as prognostic markers in an attempt to predict involvement of axillary lymph nodes and histological grade using logistic regression. Prediction was 70% for both nodal status and histological analyses. The outcome of this study is compared to an earlier study using the same cytological information to obtain prediction using a neural approach. Using artificial neural networks, prediction accuracy was 87% and 82% for nodal status and histological assessment, respectively. This study also attempts to identify the impact of individual prognostic factors. The statistical approach identified S-phase fraction and DNA-ploidy as the most important prediction markers for nodal status and histological assessment analyses. A comparison was made between these two quantitative techniques.

Expression of metastasis-associated genes h-mts1 (S100A4) and nm23 in carcinoma of breast is related to disease progression.

The murine 18A2/mts1 and its human homolog h-mts1 (S100A4), encoding a Ca2+-binding protein belonging to the S-100 family, are associated with high invasive and metastatic potentials of murine tumors, human tumor cell lines in vitro, and human tumors growing as xenografts. The nm23 is a putative metastasis-suppressor gene whose expression has been found to correlate inversely with the metastatic potential of some forms of human cancer. The products of both human genes alter cytoskeletal dynamics, with antagonistic effects. In view of the equivocal association of nm23 with the metastatic potential of human cancer, we suspected that the relative expression of h-mts1 and nm23 might reflect tumor progression more accurately than either of them alone. We describe here the expression of these genes in infiltrating ductal carcinomas of the breast and show that high h-mts1 expression is associated with metastatic spread to the regional lymph nodes. The expression of nm23 on its own did not show a statistically significant inverse correlation with nodal spread. However, the expression status of the two genes, taken together, correlated strongly with the occurrence of nodal metastases. Breast cancers with no detectable expression of h-mts1 were found to be estrogen and progesterone receptor positive. Expression of h-mts1 was not related to tumor differentiation. The clinical data, together with the state of expression of steroid receptors and the expression levels of h-mts1 and nm23 genes, were analyzed using artificial neural networks for accuracy in predicting nodal spread of the carcinomas. These analyses support the conclusion that, overall, h-mts1 expression appears to be associated with and indicative of more aggressive disease. Complemented with nm23, h-mts1 could provide a powerful marker of breast cancer prognosis.

Heat shock modulates the expression of the metastasis associated gene MTS1 and proliferation of murine and human cancer cells.

Mts1 is a metastasis-associated gene of the S-100 gene family and codes for a Ca2+-binding protein. It is highly expressed in murine and human cancers of high invasive and metastatic potential. Recent work has shown that the mts1 protein might be involved in cell cycle regulation. An upregulation of its expression drives cells into the S phase, together with an enhanced expression of p53 phosphoprotein, which has led to the suggestion that mtsl protein might be sequestering p53 thereby abrogating the G1-S checkpoint control normally exerted by p53. Preliminary studies showed that expression of mts1 is downregulated by hyperthermia. We present evidence that in murine BL6 melanoma cells and human HUT cells that hyperthermia downregulates the mts1 gene. It is also downregulated in heat-resistant variants of the B16 melanoma and HUT cells. In parallel, there is a decrease in the size of the S phase fraction and an increase in the doubling time of cells. Cell subjected to hyperthermia show an 2- to 3.5-fold increase in the expression of HSP28 which has been shown to possess a proliferation inhibitory action. It is postulated that a complete regulatory loop involving mtsl, p53, and HSP28 might be involved in cell proliferation.

Characterization of a splice variant of metastasis-associated h-mts1 (S100A4) gene expressed in human infiltrating carcinomas of the breast.

The h-mts1 (S100A4) is a member of the S100 gene family, coding for a calcium-binding protein. It is a metastasis-associated gene whose expression shows strong correlation with the proliferative potential and invasive and metastatic ability of cancers. In a proportion of human intraductal carcinomas of the breast, a shorter variant h-mts1 transcript (h-mts1v) of approximately 450 nucleotides is expressed. We have characterized the transcript using reverse transcriptase-polymerase chain reaction employing exon-specific oligonucleotides. We show here that the noncoding exon 1a/1b is lost in the variant cDNA. Exons 2 and 3, which code for the protein, seem to be present in the variant isoform. The RT-PCR products obtained using exons 2- and 3-specific oligonucleotides showed a high degree of sequence homology with exons 2 and 3 of the h-mts1 gene. The expression of the variant transcript could be influencing disease progression, albeit not as effectively as the normal unspliced h-mts1 transcript.

Expression of the transmembrane glycoprotein CD44 and metastasis associated 18A2/MTS1 gene in B16 murine melanoma cells.

CD44 is a transmembrane cell adhesion-mediating protein which occurs as alternatively spliced isoforms in a variety of cell types. CD44 isoforms have been reported to be differentially expressed in cancers and the isoform CD44v6 has often been associated with metastatic potential. The 18A2/mts1 gene, which codes for a Ca(2+)-binding protein of the S-100 family, is a metastasis associated gene and its expression has been shown to be related to cell proliferation, cancer metastasis and invasion. The association of 18A2/mts1 expression with invasion has been attributed to its ability to promote depolymerisation of cytoskeletal elements and it appears to also participate in the remodelling of the extracellular matrix. Here we have examined the expression of CD44v6 in metastatic variants of the B16 melanoma with different levels of 18A2/mts1 expression. We found that metastatic potential was not related to the overall CD44 expression as detected by immunostaining; the high metastasis variant ML8 showed reduced CD44v6 positivity as compared with the low metastasis variant F1. Up-regulation of 18A2/mts1 expression in F1 cells by a-melanocyte stimulating hormone (MSH) and its down-regulation in ML8 cells by RA reduced the numbers of CD44v6 staining cells. In F1 cells the glycoprotein was found to be uniformly associated with the cell membrane. But in F1 cells treated with a-MSH where 18A2/mts1 expression was up-regulated, CD44v6 showed redistribution into a patchy focal pattern. This patchy focal distribution of CD44v6 also occurred in ML8 cells which express 18A2/mts1 at a high level. It is suggested that the patching of CD44v6 molecules is a consequence of the changes in cytoskeletal dynamics brought about by 18A2/mts1 expression, that are conducive to aggregation and patching of these transmembrane glycoproteins. It is postulated that this induction of patching could provide discrete and strong adhesive foci promoting cell adhesion and invasive behaviour.