We are interested in two aspects of a given type of metastatic breast cancer: which potentially cancer-relevant genes are expressed and which factors determine invasiveness. Using reverse transcription real-time PCR, we detected gene expression of 26 matrix metalloproteinases (MMPs) in MDA-MB-231 breast cancer cells, including those of MMP-12, MMP-16 variant 2, MMP-19, MMP-20, MMP-21, MMP-23, MMP-24, MMP-25, MMP-25 variant 2, MMP-L1, MMP-26, MMP-27, and MMP-28, in contrast to the 13 MMPs detected until now in these cells. We found that MMP genes are expressed at widely different levels in these cells, over five orders of magnitude. After individual siRNA-induced depletions, we found that six additional species of cancer cell MMPs promote invasiveness in MDA-MB-231 cells: MMP-3, MMP-11, MMP-12, MMP-17, MMP-19, and MMP-23, thus raising the total to 12 endogenous MMPs which do so in these cells. The data support the conclusion that some cancer cell MMPs, although expressed at low levels, are needed for cancer trait in MDA-MB-231 cells, and that several endogenous MMPs play non-redundant roles in this process. The mRNA level of MMP-11, but not of other MMPs, rose substantially following individual siRNA-targeted depletion of cancer cell MMP-17 mRNA, while no MMP mRNA increased appreciably after degradation of other MMP mRNAs. This supports the conclusion that MMP-17 may be a member of an intracellular signaling pathway which downregulates MMP-11 mRNA.

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AP-2alpha, interleukin-4 (IL-4), E-cadherin, fibulin 1D, p16(INK4alpha), PTEN, RKIP, and S100A4 are determinants (suppressors, except for S100A4) of cancer cell invasiveness and other traits of cancer progression, which are located upstream of matrix metalloproteinases (MMPs) in cell signaling pathways. We will refer to them as upstream cancer-progression determinants (UCPDs, for brevity). MMP-1, MMP-2, MMP-9, MMP-11, MMP-13, MMP-14, MMP-16, and MMP-19 are enhancers of cancer cell invasiveness and other traits of cancer progression, in MDA-MB-231 breast cancer cells. We are interested in pathway links from UCPDs to gene expression of cancer cell MMPs in MDA-MB-231 cells. To test models about these links, wild-type copies of UCPDs were transiently overexpressed and then MMP mRNAs were measured by reverse transcription real-time PCR. The present results show that each of eight UCPDs is linked to the gene expression of a unique set of MMPs. This indicates that the effects are sequence-specific and that each UCPD reaches these MMP expressions through different sets of signaling pathways. We have detected 20 new pathway links, 11 are downregulatory and nine are upregulatory; 15 are new links in any cell, and five are new links in breast cancer. In seven links, three cancer-progression suppressing UCPDs unexpectedly enhance the gene expression of five cancer-progression promoting MMPs.

Rictor and its binding partner Sin1 are indispensable components of mTORC2 (mammalian Target of Rapamycin Complex 2). The mTORC2 signaling complex functions as the regulatory kinase of the distinct members of AGC kinase family known to regulate cell proliferation and survival. In the early chemotaxis studies in Dictyostelium, the rictor's ortholog has been identified as a regulator of cell migration. How rictor regulates cell migration is poorly characterized. Here we show that rictor regulates cell migration by controlling a potent inhibitor of Rho proteins known as the Rho-GDP dissociation inhibitor 2 (RhoGDI2). Based on our proteomics study we identified that the rictor-dependent deficiency in cell migration is caused by up-regulation of RhoGDI2 leading to a low activity of Rac and Cdc42. We found that a suppression of RhoGDI2 by rictor is not related to the Sin1 or raptor function that excludes a role of mTORC2 or mTORC1 in regulation of RhoGDI2. Our study reveals that rictor by suppressing RhoGDI2 promotes activity of the Rho proteins and cell migration.