The importance of apoptosis as a means of homeostasis and maintaining genomic integrity, as well as the ability of cancer cells to escape this failsafe mechanism, has long been the subject of intense investigation. To investigate the possibility that prolactin might enable breast cancer cells to survive apoptotic insults, we stimulated T47-D and MCF-7 cells with ceramide (C2) and assessed the ability of prolactin to improve cell survival. Morphological studies and cell survival assays demonstrated a significant survival effect in T47-D cells exposed to prolactin. Because prolactin activates the Jak2-STAT5 pathway, we then proceeded to create a model in which the role of this pathway in apoptosis could be investigated. An initial attempt to inhibit dexamethasone-induced apoptosis in a human leukaemic cell line (CEM-C7) by establishing a stable clone expressing the prolactin receptor (for activating the JAK2-STAT5 pathway) was unsuccessful. Next, we established stable clones of breast cancer cells overexpressing STAT5b. Despite increased STAT5 signalling after prolactin stimulation, no enhancement of survival was demonstrated, implying that STAT5b is not responsible for survival following ceramide exposure. Surprisingly, increased STAT5 activation, following prolactin stimulation, actually increased cell death. The second half of this project involved investigation and characterization of the newly identified Met protein, which we showed to induce apoptosis in breast cancer cells as well as in other cell lines. Met is structurally related to SAF-B - which attaches to DNA at scaffold / matrix attachment regions and is thought to be involved in DNA transcription or mRNA processing. Met was shown to be confined to the nucleus, and partially co-localized with SAF-B, but not with splicing factor speckles. Signalling assays show that Met downregulates transcriptional activity within cells.