Anti-invasion drugs

Attacking breast cancer at the preinvasion stage by targeting autophagy

Preinvasive breast carcinoma cells that proliferate and accumulate within the nonvascular, closed intraductal niche are under severe hypoxic and metabolic stress. Understanding the survival mechanisms used by these cells has revealed therapeutic strategies for killing preinvasive neoplasms. We have found that autophagy ('self-eating') is a major survival strategy used by preinvasive carcinoma and breast cancer stem-like cells. Based on this finding, we have opened a clinical trial that is exploring neoadjuvant oral chloroquine antiautophagy therapy for ductal carcinoma in situ. We envision that antiautophagy therapy can be administered in combination with other treatments such as those that elevate intracellular calcium, to create a state of intolerable stress for preinvasive neoplastic cells, and thereby stop breast cancer before it starts.

Low-dose oral methotrexate and cyclophosphamide in metastatic breast cancer: antitumor activity and correlation with vascular endothelial growth factor levels

BACKGROUND

Anticancer chemotherapy is thought to be effective by means of direct cytotoxicity on tumor cells. Alternative mechanisms of efficacy have been ascribed to several common anticancer agents, including cyclophosphamide (CTX), methotrexate (MTX), anthracyclines and taxanes, postulating an antiangiogenic activity.

PATIENTS AND METHODS

We evaluated the clinical efficacy and impact on serum vascular endothelial growth factor (VEGF) levels of low-dose oral MTX and CTX in patients with metastatic breast cancer. MTX was administered 2.5 mg bd on days 1 and 2 each week and CTX 50 mg/day administered continuously.

RESULTS

Sixty-four patients were enrolled, 63 were evaluable: Eastern Cooperative Oncology Group (ECOG) performance status 0-1, > or =2 sites of metastatic disease (n = 50 patients), progressive disease at study entry (n = 51), 1 regimen for metastatic disease (n = 32) and > or =2 regimens (n = 20). Among the 63 evaluable patients, there were two complete remissions (CR), 10 partial remissions (PR) for an overall response rate of 19.0% (95% CI 10.2% to 30.9%) and an overall clinical benefit (CR+ PR+ stable disease >24 weeks) of 31.7% (95% CI 20.6% to 44.7%). Grade > or =2 leucopenia was registered in only 13 patients. The median serum VEGF level for the subgroup of patients on treatment for at least 2 months decreased with treatment from 315 pg/ml (95% CI 245 to 435) at baseline to 248 pg/ml (95% CI 205 to 311) at 2 months (P <0.001). Both responders and non-responders showed similar reductions in serum VEGF (P = 0.78). After 6 months patients still on treatment had a median VEGF level of 195 pg/ml (95% CI 96 to 355), which was significantly lower than the median baseline values (P = 0.001).

CONCLUSIONS

Continuously low-dose CTX and MTX is minimally toxic and effective in heavily pretreated breast cancer patients. A drop in VEGF was associated with the treatment and so alternative hypotheses, other than that of direct toxicity on tumor cells, must be favored when trying to explain the anticancer effect.

Cell motility is inhibited by the antiepileptic compound, valproic acid and its teratogenic analogues

Valproic acid (VPA) is an established human teratogen that causes neural tube defects in 1-2% of human foetuses exposed to the drug during early pregnancy. In this study, individual cell motility was evaluated using short- and long-term time-lapse video-recording and computer assisted image analysis, and it was found that VPA and selected VPA-analogues inhibited individual cell motility of L-cells in a dose-dependent manner. The compounds caused a decrease in the root-mean-square speed, S, and in the rate of diffusion, R, but an increase in the time of persistence in direction, P. Using short-term recordings and measurements of mean-cell speed, the reduction in the motile behaviour was shown to correlate with the teratogenic potency of the tested compounds. The observed effects of VPA on cell motility was independent of the employed L-cell clone, and could be reproduced in cells containing the neuronal marker NCAM and in the neuronal cell line N2a. Furthermore, the observed effect was independent of culture substratum, being observed for L-cells grown on fibronectin as well as on plastic. Immunofluorescence microscopy revealed that VPA-treatment of mouse L-cells caused a redistribution of F-actin and of a series of focal adhesion proteins, indicating that the effect of VPA on cell motility may be causally related to increased cell-substratum interactions or to alterations in the organisation or dynamics of the actin cytoskeleton.

Tumor invasion: role of growth factor-induced cell motility

Cancer progression to the invasive and metastatic stage represents the most formidable barrier to successful treatment. To develop rational therapies, we must determine the molecular bases of these transitions. Cell motility is one of the defining characteristics of invasive tumors, enabling tumors to migrate into adjacent tissues or transmigrate limiting basement membranes and extracellular matrices. Invasive tumor cells have been demonstrated to present dysregulated cell motility in response to extracellular signals from growth factors and cytokines. Recent findings suggest that this growth factor receptor-mediated motility is one of the most common aberrations in tumor cells leading to invasiveness and represents a cellular behavior distinct from-adhesion-related haptokinetic and haptotactic migration. This review focuses on the emerging understanding of the biochemical and biophysical foundations of growth factor-induced cell motility and tumor cell invasiveness, and the implications for development of targeted agents, with particular emphasis on signaling from the epidermal growth factor (EGF) and hepatocyte growth factor (HGF) receptors, as these have most often been associated with tumor invasion. The nascent models highlight the roles of various intracellular signaling pathways including phospholipase C-gamma (PLC gamma), phosphatidylinositol (PI)3'-kinase, mitogen-activated protein (MAP) kinase, and actin cytoskeleton-related events. Development of novel agents against tumor invasion will require not only a detailed appreciation of the biochemical regulatory elements of motility but also a paradigm shift in our approach to and assessment of cancer therapy.

Proline-rich antimicrobial peptide, PR-39 gene transduction altered invasive activity and actin structure in human hepatocellular carcinoma cells

PR-39 is an endogenous proline-rich antimicrobial peptide which induces the synthesis of syndecan-1, a transmembrane heparan sulphate proteoglycan involved in cell-to-matrix interactions and wound healing. Previously, we revealed that the expression of syndecan-1 was reduced in human hepatocellular carcinomas with high metastatic potential and speculated that syndecan-1 played an important role in inhibition of invasion and metastasis. It is assumed that a modification of this process with PR-39 and syndecan-1 may result in a new strategy by which it can inhibit the invasion and metastasis. Therefore, we transduced a gene of PR-39 into human hepatocellular carcinoma cell line HLF, which shows a low expression of syndecan-1 and a high in vitro invasive activity, and examined whether this procedure could reduce the invasive activity of tumour cells. In two transfectants with PR-39 gene, the syndecan-1 expression was induced and the invasive activity in type I collagen-coated chamber was inhibited. Moreover, these transfectants showed the suppression of motile activity assayed by phagokinetic tracks in addition to the disorganization of actin filaments observed by a confocal imaging system. In contrast, five transfectants with syndecan-1 gene in the HLF cells revealed suppression of invasive activity but did not alter the motile activity and actin structures of the cell. These results suggest that PR-39 has functions involved in the suppression of motile activity and alteration of actin structure on human hepatocellular carcinoma cells in addition to the suppression of invasive activity which might result from the induction of syndecan-1 expression.

Regulation of motility and protease expression in PKC-mediated induction of MCF-7 breast cancer cell invasiveness

We investigated a potentially central role of protein kinase C (PKC) in controlling multiple pathways in breast cancer cell invasiveness. To do this we evaluated the ability of pharmacologic agents that alter PKC activity to regulate the behavior of the poorly invasive human breast cancer cell line MCF-7. Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) produced a dramatic induction of the invasiveness of these cells (18-fold), an effect that concurrent treatment with the PKC inhibitor Bryostatin-1 was able to block. To characterize alterations in the cellular properties that might be responsible for these effects we measured the impact of these two agents on a number of processes thought to be important for invasiveness. The motility of the cells was first examined; it was markedly increased by treatment with TPA (20-fold) and again, Bryostatin-1 inhibited this stimulation. We next examined the expression of MMP-1, 3, 9, 10, and 11 (matrix metalloproteinases), all of which have been shown to be PKC responsive in other systems. We found that the expression and secretion of MMP-9 were increased by at least 100-fold, though all of the enzyme secreted was in the latent form. Finally, the expression of both urokinase plasminogen activator (UPA) and its receptor (UPAR) were induced after TPA treatment by 8- and 7-fold, respectively. In conclusion, we have shown that stimulation of PKC activity markedly increases the invasiveness of MCF-7 cells, and that this change in behavior is correlated with a coordinated set of biochemical and cellular changes which are likely to contribute to this process. These data highlight the possible utility of PKC inhibitors such as Bryostatin-1 as anti-invasive and/or antimetastatic agents. Bryostatin-1 is currently in early clinical trials as an anticancer agent.

Novel endocrine therapies in breast cancer

Endocrine therapy of breast cancer consists of a variety of both medical and surgical ablative treatment modalities, but ablative therapy is increasingly replaced by medical treatment. Most endocrine therapies have more than one endocrine effect, frequently together with direct growth inhibitory actions via receptors. Endocrine therapy can be effective in all phases of the disease, but curative only in early disease while in advanced cancer it can only prolong survival. In the past decade the number of available endocrine agents has been drastically increased. Novel approaches in the endocrine therapy of breast cancer are application of new antiestrogens, antiprogestins, new potent aromatase inhibitors, analogues of luteinizing hormone-releasing hormone (LHRH-A) and somatostatin, inhibitors of prolactin secretion, vitamin A and D analogues, bisphosphonates, growth factor antagonists, tyrosine protein kinase inhibitors, protease inhibitors, inhibitors of angiogenesis, radiolabeled hormones and monoclonal antibodies. New cell biological factors such as oncogenes and suppressorgenes, secretory proteins and membrane receptors can be used not only as prognostic factors but also for prediction of type of response to endocrine and chemotherapy. Thus, these cell biological parameters can be used to select high and low risk patients, type of systemic treatment, and can also be used as targets for new treatment modalities. Future studies on treatment of all stages of disease will increasingly focus on promising combined treatment modalities.