Consistent with the findings that MMPs, produced by tumour cells, enhance OC degradation by prior removal of the overlying unmineralized layer [31], MMP-13 released by PTHrP or IL-8 primed MDA-MB-231 cells affected bone resorption (that is, OC activation and function), an activity that was fully inhibited by GM6001 and partially by CL-82198. This evidence concerns the gene MMP13 and neoplasm.