A perspective on the metastasis suppressor field

Metastasis is the leading cause of cancer patient mortality. Metastasis suppressors are genes that, upon reexpression in metastatic tumor cells to levels observed in their nonmetastatic counterparts, significantly reduce metastasis without affecting the growth of the primary tumor. Analysis of > 30 metastasis suppressors revealed complex mechanisms of action that include multiple signaling pathways, transcriptional patterns, posttranscriptional regulatory mechanisms, and potential contributions of genomic stability. Clinical testing of strategies to re-establish a validated metastasis suppressor pathway in tumors is best directed to the adjuvant setting, with the goal of inhibiting the outgrowth of occult micrometastases.

The Clinical Implications of RSK1-3 in Human Breast Cancer

BACKGROUND/AIM

The ribosomal S6 protein kinase (RSK) family is an important effector of extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) that could influence tumour metastasis by phosphorylating proteins in both the nuclear and cytoplasmic compartments. Aberrant expression of RSK is evident in certain malignancies but the role played by RSK in breast cancer is still not clear. This study aimed to examine the expression of RSK in human breast cancer specimens and its role to breast cancer metastasis.

MATERIALS AND METHODS

The expression of RSK1 to -3 were separately examined in human breast cancer tissues (normal, n=33; cancer, n=112) using quantitative real-time polymerase chain reaction (Q-PCR) and immunohistochemistry. Migration and adhesion of breast cancer cells treated with the RSK inhibitor SL0101 were investigated by electric cell impedance sensing (ECIS). The effect on growth and invasion of RSK1-3 was then investigated using in vitro models.

RESULTS

The clinical data and immunohistochemistry revealed that expression of RSK1 and RSK3 were less in tumour tissues than normal. mRNA expression of RSK2 was negatively correlated with grade, TNM staging, and survival rate. SL0101 inhibited adhesion of the MCF-7 and MDA-231 breast cancer cell lines. SL0101 suppressed MDA-231 invasion and the alternate RSK inhibitor BRD7389 inhibited the invasion of MCF-7 and MDA-231 cells.

CONCLUSION

RSK1 and 3 but not RSK2 are down-regulated in breast tumour and are associated with disease progression. RSK may be a key component in the progression and metastasis of breast cancer.

Functional localization of metastasis suppressor genes for hepatocellular carcinoma on human chromosome 8p21.1-23.1

AIM: To further refine the region harboring the metastasis suppressor genes in the human chromosome 8p21.1-23.1, and to pave the way for finding and cloning novel metastasis suppressor genes.

METHODS: The STS primer sequences were found according to the National Center for Biotechnology Information Database (NCBI). C5F genomic DNA and A9/neo8 genomic DNA were used as negative and positive controls for chromosome 8 amplification, respectively. Genomic DNA was isolated and quantified from cultured hybrid clones. A9/C5F-1 and A9/C5F-2 microcell hybrid clones were used as metastasis-unsuppressed groups, while A9/C5F-4, A9/C5F-8 and A9/C5F-10 clones were used as metastasis-suppressed groups. STS-PCR products were separated by electrophoresis.

RESULTS: STS markers were preserved in metastasis-suppressed microcell hybrid clones (A9/C5F-4, A9/C5F-8 and A9/C5F-10), such as D8S552 (12786562-12786681), D8S1733(22576582-22576836), D8S1734 (22851217-22851336), D8S254(16652480-16652550) and D8S1973 (28681110-28681363) on human chromosome 8p21.1-23.1. In contrast, STS markers were lost in metastasis-unsuppressed clones (A9/C5F-1 and A9/C5F-2) in this region.

CONCLUSION: The metastasis suppressor genes may be located within the interval between D8S542 and D8S1973 on human chromosome 8p21.1-23.1.