Detection of candidates for cancer cell motility inhibitory protein in the Dunning adenocarcinoma model

Defining the biologic role of genes that regulate prostate cancer metastasis

Metastasis is the most lethal attribute of a cancer. There is a critical need for markers that will accurately distinguish those histologic lesions and disseminated cells that have a high probability of causing clinically important metastatic disease from those cells that will remain indolent. Despite the explosion in new information regarding the genetics of cancer, only six human genes have thus far been shown to functionally suppress metastasis. The present review and perspective describes the evolving view of the mechanisms that regulate metastasis, and the importance of metastasis-suppressor genes in this process. Specifically, the clinical problem of metastatic prostate cancer, the identification of metastatic colonization as a therapeutic target, and the identification and functional characterization of prostate cancer metastasis-suppressor genes are discussed.

Induction of autocrine factor inhibiting cell motility from murine B16-BL6 melanoma cells by alpha-melanocyte stimulating hormone

We have previously reported that neuropeptide alpha-melanocyte stimulating hormone (alpha-MSH) successfully inhibited Matrigel invasion and haptotactic migration of B16-BL6 melanoma cells towards both fibronectin and laminin without affecting their growth. In the present study, we investigated the inhibitory mechanism of tumor cell motility by alpha-MSH. Alpha-MSH significantly blocked the autocrine motility factor (AMF)-enhanced cell motility. However, alpha-MSH did neither prevent the secretion of AMF from B16-BL6 cells nor alter the expression level of AMF receptor (gp78). On the other hand, alpha-MSH induced the secretion of the motility inhibitory factor(s) from B16-BL6 cells in a concentration- and time-dependent manner. The induction of the motility inhibitor(s) was proportional to increasing levels of intracellular cAMP induced by alpha-MSH as well as forskolin, and the activity was abolished by an adenylate cyclase inhibitor, 2',5'-dideoxyadenosine (DDA). The motility-inhibiting activity in conditioned medium (CM) from alpha-MSH-treated B16-BL6 cells was found to have a m.w. below 3 kDa after fractionation. This activity was abolished by boiling but insensitive to trypsin. The treatment of tumor cells with cycloheximide reduced the activity in alpha-MSH-stimulated CM. Our results suggest that alpha-MSH inhibited the motility of B16-BL6 cells through induction of autocrine factor(s).

The role of motility proteins and metastasis-suppressor genes in prostate cancer progression

In 1996, an estimated 317,000 new cases of prostate cancer will be diagnosed in the United States. The incidence of prostate cancer has more than doubled in the past five years; in fact, it is estimated that aggressive screening starting at age 50 could potentially identify 10,000,000 American men with histologically localized prostate cancer. In order to reduce deaths from prostate cancer, it is necessary not only to diagnose but also to accurately predict the clinical course of an individual patient's cancer, thus allowing for more effectively directed treatment. Acquisition of metastatic ability is a well-recognized criterion for the aggressiveness of prostate cancer. A number of molecular and cellular changes associated with the malignant progression of prostate cancer have been identified. Certain of these changes may potentially be used as markers for metastatic ability of histologically localized prostate cancer cells. This concise review will consider two parameters which are associated with the acquisition of metastatic ability: increased cellular motility and loss of metastasis-suppressor gene function. A link between these two parameters has been demonstrated and may contribute to the development of innovative approaches for predicting the metastatic ability of individual tumors.