PTHLH and breast cancer: Gene Set Enrichment Analysis (GSEA) of these data revealed that in cells lacking the PTHrP NLS, there was a significant enrichment for genes that are upregulated in MCF7 cells overexpressing the oncoprotein and cell cycle promoter, cyclin D1 (Fig. 3B), indicating that the PTHrP NLS modulates the expression of cell cycle regulators to alter proliferation in MCF7 breast cancer cells.