SerpinB2 (aka plasminogen activator type 2) is well described as an extracellular inhibitor of urokinase-type plasminogen activator (uPA). However, the majority of SerpinB2 is retained intracellularly, and many uPA-independent activities have been reported for SerpinB2 suggesting an alternate function. This thesis explores the role of SerpinB2 in epithelial tumour cell lines, highlights the problems associated with various expression systems and argues that SerpinB2 has no role in growth or apoptosis of tumour cells. A potential role for immune modulation and angiogenesis is suggested in in vivo models. Previous research using SerpinB2 transfected, clonally selected tumour cell lines suggested that SerpinB2 regulates the retinoblastoma tumour suppressor protein (Rb) by binding and protecting Rb from degradation. Despite the use of two techniques under numerous conditions and positive controls, no significant interaction between SerpinB2 and Rb was found. SerpinB2 was reported to bind Rb through a PENF homology motif located within the SerpinB2 C-D interhelical loop region. The PENF homology motif was postulated to represent the motif responsible for binding to the C-pocket of Rb. Epstein Barr Virus nuclear antigen 6 (EBNA6) is a known Rb binding protein, which contains two predicted PENF homology motifs. However, mutation of the two PENF homology motifs within EBNA6 did not reduce Rb binding. Furthermore, the SerpinB2 PENF homology motif is actually not well conserved between SerpinB2 proteins from multiple species, whereas other regions of the SerpinB2 C-D loop show a high level of conservation. These data do not support a role for SerpinB2 and the PENF homology motif in Rb binding. SerpinB2 has been proposed to have a role in regulating growth and apoptosis. To further investigate this proposed phenotype of SerpinB2, SerpinB2 was expressed in a range of epithelial tumour lines using transient transfection. No change in growth, apoptosis or Rb levels were found. After ≈2-3 month antibiotic selection for the SerpinB2-expressing plasmid, SerpinB2 protein was lost without the loss of the transgene, indicating selective pressure against long-term SerpinB2 protein expression. To further investigate long-term SerpinB2 expression adenovirus and lentivirus vectors were used. Infection of tumour cell lines with adenovirus vectors expressing SerpinB2 resulted in reduced cell growth, characterised by increased p53 (but not Rb) levels and G2 arrest or apoptosis. When SerpinB2 expressing lentivirus vectors were used to transduce the same tumour cell lines, high levels of long-term expression of functional SerpinB2 was achieved. However, SerpinB2-expressing cell lines showed no differences in growth, proliferation, Rb levels, or apoptosis induced by a range of agents. Growth and apoptosis observed with adenovirus SerpinB2 had all the characteristics of adenovirus-associated toxicity, which has been reported previously for specific proteins. These experiments highlighted the problems associated with SerpinB2 expression systems and suggest that SerpinB2 expression per se is not toxic nor has a role in regulating Rb, growth and apoptosis. Screening of a number of tumour cell lines identified the HPV16 transformed cervical cancer line as expressing high levels of SerpinB2. SerpinB2 was located both extracellularly and intracellularly with a cytoplasmic and nuclear distribution. A high molecular weight SerpinB2 species was identified in CaSki cells and was shown to be the N-linked glycosylated species. Sequencing showed the protein to be Type A SerpinB2 and the protein was shown to form an inhibitory complex with uPA. An abundant low molecular weight SerpinB2 species was also identified in CaSki cell supernatants and appeared to be a proteolytic fragment of SerpinB2. Treatment of CaSki with PMA, TNFα and IFNγ increased SerpinB2 levels. Lentiviral based shRNA failed to significantly down regulate SerpinB2 expression and increasing SerpinB2 levels with lentiviral expression did not change growth, apoptosis, Rb levels or E7 transcription. Lentiviral expression of SerpinB2 in (normally SerpinB2 negative) HPV16 transformed SiHa cells, also failed to show changes in Rb levels or E7 transcription. CaSki thus express wild-type and functional SerpinB2, but no evidence could found that SerpinB2 effects HPV16 E7 transcription or Rb levels. The data presented identifies CaSki as valuable source of biologically functional SerpinB2. SerpinB2 expression in breast cancer cells has been associated with positive prognosis. Tubo, a SerpinB2-negative murine breast carcinoma cell line, was transduced with lentivirus expressing SerpinB2 and grown subcutaneously in BALB/c mice. SerpinB2 expressing tumours appeared red and were larger than control tumours. Furthermore, SerpinB2 expressing tumours had a ≈2 fold higher density of blood vessels when compared to Tubo and Tubo expressing EGFP. Mice carrying tumours expressing SerpinB2 also showed reduced anti-tumour IgG2 responses. These data suggest that a role for SerpinB2 in regulating angiogenesis and antitumour immunity. In conclusion, this thesis challenges the notion that SerpinB2 regulates Rb, cell cycle, and apoptosis and suggests a potential role for SerpinB2 in tumour angiogenesis and immunity.

SerpinB2 (aka plasminogen activator type 2) is well described as an extracellular inhibitor of urokinase-type plasminogen activator (uPA). However, the majority of SerpinB2 is retained intracellularly, and many uPA-independent activities have been reported for SerpinB2 suggesting an alternate function. This thesis explores the role of SerpinB2 in epithelial tumour cell lines, highlights the problems associated with various expression systems and argues that SerpinB2 has no role in growth or apoptosis of tumour cells. A potential role for immune modulation and angiogenesis is suggested in in vivo models. Previous research using SerpinB2 transfected, clonally selected tumour cell lines suggested that SerpinB2 regulates the retinoblastoma tumour suppressor protein (Rb) by binding and protecting Rb from degradation. Despite the use of two techniques under numerous conditions and positive controls, no significant interaction between SerpinB2 and Rb was found. SerpinB2 was reported to bind Rb through a PENF homology motif located within the SerpinB2 C-D interhelical loop region. The PENF homology motif was postulated to represent the motif responsible for binding to the C-pocket of Rb. Epstein Barr Virus nuclear antigen 6 (EBNA6) is a known Rb binding protein, which contains two predicted PENF homology motifs. However, mutation of the two PENF homology motifs within EBNA6 did not reduce Rb binding. Furthermore, the SerpinB2 PENF homology motif is actually not well conserved between SerpinB2 proteins from multiple species, whereas other regions of the SerpinB2 C-D loop show a high level of conservation. These data do not support a role for SerpinB2 and the PENF homology motif in Rb binding. SerpinB2 has been proposed to have a role in regulating growth and apoptosis. To further investigate this proposed phenotype of SerpinB2, SerpinB2 was expressed in a range of epithelial tumour lines using transient transfection. No change in growth, apoptosis or Rb levels were found. After ≈2-3 month antibiotic selection for the SerpinB2-expressing plasmid, SerpinB2 protein was lost without the loss of the transgene, indicating selective pressure against long-term SerpinB2 protein expression. To further investigate long-term SerpinB2 expression adenovirus and lentivirus vectors were used. Infection of tumour cell lines with adenovirus vectors expressing SerpinB2 resulted in reduced cell growth, characterised by increased p53 (but not Rb) levels and G2 arrest or apoptosis. When SerpinB2 expressing lentivirus vectors were used to transduce the same tumour cell lines, high levels of long-term expression of functional SerpinB2 was achieved. However, SerpinB2-expressing cell lines showed no differences in growth, proliferation, Rb levels, or apoptosis induced by a range of agents. Growth and apoptosis observed with adenovirus SerpinB2 had all the characteristics of adenovirus-associated toxicity, which has been reported previously for specific proteins. These experiments highlighted the problems associated with SerpinB2 expression systems and suggest that SerpinB2 expression per se is not toxic nor has a role in regulating Rb, growth and apoptosis. Screening of a number of tumour cell lines identified the HPV16 transformed cervical cancer line as expressing high levels of SerpinB2. SerpinB2 was located both extracellularly and intracellularly with a cytoplasmic and nuclear distribution. A high molecular weight SerpinB2 species was identified in CaSki cells and was shown to be the N-linked glycosylated species. Sequencing showed the protein to be Type A SerpinB2 and the protein was shown to form an inhibitory complex with uPA. An abundant low molecular weight SerpinB2 species was also identified in CaSki cell supernatants and appeared to be a proteolytic fragment of SerpinB2. Treatment of CaSki with PMA, TNFα and IFNγ increased SerpinB2 levels. Lentiviral based shRNA failed to significantly down regulate SerpinB2 expression and increasing SerpinB2 levels with lentiviral expression did not change growth, apoptosis, Rb levels or E7 transcription. Lentiviral expression of SerpinB2 in (normally SerpinB2 negative) HPV16 transformed SiHa cells, also failed to show changes in Rb levels or E7 transcription. CaSki thus express wild-type and functional SerpinB2, but no evidence could found that SerpinB2 effects HPV16 E7 transcription or Rb levels. The data presented identifies CaSki as valuable source of biologically functional SerpinB2. SerpinB2 expression in breast cancer cells has been associated with positive prognosis. Tubo, a SerpinB2-negative murine breast carcinoma cell line, was transduced with lentivirus expressing SerpinB2 and grown subcutaneously in BALB/c mice. SerpinB2 expressing tumours appeared red and were larger than control tumours. Furthermore, SerpinB2 expressing tumours had a ≈2 fold higher density of blood vessels when compared to Tubo and Tubo expressing EGFP. Mice carrying tumours expressing SerpinB2 also showed reduced anti-tumour IgG2 responses. These data suggest that a role for SerpinB2 in regulating angiogenesis and antitumour immunity. In conclusion, this thesis challenges the notion that SerpinB2 regulates Rb, cell cycle, and apoptosis and suggests a potential role for SerpinB2 in tumour angiogenesis and immunity.

The retinoblastoma tumor suppressor (pRb) is thought to orchestrate terminal differentiation by inhibiting cell proliferation and apoptosis and stimulating lineage-specific transcription factors. In this thesis I have shown that in the absence of pRb, differentiating primary myoblasts fused to form short myotubes that never twitched and degenerated via a non-apoptotic mechanism. The shortened myotubes exhibited an impaired mitochondrial network, mitochondrial perinuclear aggregation, autophagic degradation and reduced ATP production. Bcl-2 and autophagy inhibitors restored mitochondrial function and rescued muscle degeneration, leading to twitching myotubes that expressed normal levels of muscle-specific proteins and eventually exited the cell-cycle. A hypoxia-induced glycolytic switch also rescued the myogenic defect after chronic or acute inactivation of Rb in a HIF-1-dependent manner. These results demonstrate that pRb is required to inhibit apoptosis in myoblasts and autophagy in myotubes but not to activate the differentiation program. I next tested the effect of retinoblastoma protein family members – p107 and p130 – on skeletal myogenesis in the absence of Rb. Chronic or acute inactivation of Rb plus p130 or Rb plus p107 increased myoblast cell death and reduced myotube formation, yet expression of Bcl-2, treatment with autophagy antagonist or exposure to hypoxia extended myotube survival, leading to long, contracting myotubes that appeared indistinguishable from control myotubes. Triple mutations in Rb family genes further accelerated cell death and led to elongated myocytes or myotubes containing two nuclei, some of which survived and twitched under hypoxia. Whereas nuclei in Rb-/- myotubes were unable to stably exit the cell-cycle, myotubes lacking both p107/p130 became permanently post-mitotic, suggesting that pRb, but not p107 or p130 may be lost in cancer because of the unique requirement for cell-cycle exit during terminal differentiation. This thesis demonstrates that pRb is required to inhibit apoptosis in myoblasts and autophagy in myotubes but not to activate the differentiation program, and reveal a novel link between pRb and cell metabolism.

The retinoblastoma tumor suppressor (pRb) is thought to orchestrate terminal differentiation by inhibiting cell proliferation and apoptosis and stimulating lineage-specific transcription factors. In this thesis I have shown that in the absence of pRb, differentiating primary myoblasts fused to form short myotubes that never twitched and degenerated via a non-apoptotic mechanism. The shortened myotubes exhibited an impaired mitochondrial network, mitochondrial perinuclear aggregation, autophagic degradation and reduced ATP production. Bcl-2 and autophagy inhibitors restored mitochondrial function and rescued muscle degeneration, leading to twitching myotubes that expressed normal levels of muscle-specific proteins and eventually exited the cell-cycle. A hypoxia-induced glycolytic switch also rescued the myogenic defect after chronic or acute inactivation of Rb in a HIF-1-dependent manner. These results demonstrate that pRb is required to inhibit apoptosis in myoblasts and autophagy in myotubes but not to activate the differentiation program. I next tested the effect of retinoblastoma protein family members – p107 and p130 – on skeletal myogenesis in the absence of Rb. Chronic or acute inactivation of Rb plus p130 or Rb plus p107 increased myoblast cell death and reduced myotube formation, yet expression of Bcl-2, treatment with autophagy antagonist or exposure to hypoxia extended myotube survival, leading to long, contracting myotubes that appeared indistinguishable from control myotubes. Triple mutations in Rb family genes further accelerated cell death and led to elongated myocytes or myotubes containing two nuclei, some of which survived and twitched under hypoxia. Whereas nuclei in Rb-/- myotubes were unable to stably exit the cell-cycle, myotubes lacking both p107/p130 became permanently post-mitotic, suggesting that pRb, but not p107 or p130 may be lost in cancer because of the unique requirement for cell-cycle exit during terminal differentiation. This thesis demonstrates that pRb is required to inhibit apoptosis in myoblasts and autophagy in myotubes but not to activate the differentiation program, and reveal a novel link between pRb and cell metabolism.

The RbµE2F transcriptional regulatory pathway plays a critical role in the cell cycle. Rb is inactivated through multiple waves of phosphorylation, mediated mainly by cyclin D and cyclin E associated kinases. Once Rb is inactivated, cells can enter Sµphase. Collectively, three Rb family members and ten E2F proteins coordinate every additional stage of the cell cycle, from quiescence to mitosis. However the RbµE2F pathway is frequently altered in cancer. Aside from cell proliferation, the RbµE2F pathway regulates other essential cellular processes including apoptosis, cell differentiation, angiogenesis and DNA damage repair pathways, but its role in invasion and cancer progression is less clear. We demonstrate here that matrix metalloproteinases genes (MMPs), which regulate the invasion, migration and collagen degradation activities of cancer cells during metastasis are transcriptionally regulated by the RbµE2F pathway. Unlike E2F target genes involved in cell proliferation, which are solely regulated by the E2F activators (E2F1µ3), additional E2F family members can regulate MMP9, MMP14, and MMP15. While we had previously shown that Rafµ1 kinase physically interacts with Rb, and that disruption of this interaction with a small molecule inhibitor of the RbµRafµ1 interaction (RRDµ251) can inhibit cell proliferation, angiogenesis, and growth of tumors in mouse models, we now show RRDµ251 inhibits the expression of MMPs and the biological functions mediated by MMPs as well—including invasion, migration, and collagen degradation. RRDµ251 also inhibits metastatic foci development in a tail vein lung colonization model in mice. These results suggest that E2F transcription factors may play a role in promoting metastasis through regulation of MMP genes. Conversely, another MMP gene connected to metastasis, MMP2, is transcriptionally repressed by E2F1 in lung cancer cells through a p53µKAP1µHDAC1µmediated mechanism. However, E2F1 cannot repress the MMP2 promoter in cells that are lacking any component of this complex, such as p53 mutant breast cancer cells. Therefore the role of the RbµE2F pathway in MMP transcription and metastasis is cell type dependent. In addition to growth factors, nicotine can also induce cell proliferation, angiogenesis, EMT, and progression of lung cancer. In our studies, nicotine induced invasion, collagen degradation, and transcription of MMP2, MMP9, MMP14, and MMP15 required nAChRs, and multiple E2F family members. Our studies also show that nicotine not only promotes tumor growth in vivo through the nAChRµE2F pathway—it also results in metastasis to the liver and brain. Taken together, these studies link the RbµE2F pathway to the regulation of many facets of cancer.

The retinoblastoma tumor suppressor protein (RB) is an important regulator of the cell cycle and development. Significantly, RB is inactivated in a majority of human cancers. Thus, elucidating the function of RB will give us a better understanding of how it prevents cancer. Many decades of research have yielded a detailed understanding of the role of RB in cell proliferation through transcriptional repression of target genes. However, the precise mechanisms of its action in many cellular pathways are poorly understood, including the control of DNA replication and post-transcriptional control of gene expression. Drosophila melanogaster presents a simplified genetic system to study cancer genes. Several published observations have suggested a role for RB in regulating DNA replication. Interestingly, other data indicate that RB associates with RNA processing factors. I have characterized novel protein-protein interactions with the Drosophila retinoblastoma tumor suppressor homologue Rbf, with an emphasis on its poorly characterized N-terminal domain. I describe the interaction of Rbf with the origin recognition complex, indicating a unique connection to DNA replication control. I also show that Rbf interacts with the RNA binding protein Squid, and review the literature that suggests potential role of RB/E2F in the control of RNA processing. The ability to control RNA processing may be an additional, unappreciated mode of gene regulation by RB. A focused study of the uncharacterized amino-terminal domain of Rbf has revealed new details about the retinoblastoma tumor suppressor in cell regulation, including DNA replication and RNA processing.

Photodynamic therapy (PDT) has shown to be a promising technique to treat various forms of malignant neoplasia. The photodynamic eradication of the tumor cells is achieved by applying a photosensitizer either locally or systemically and following local activation through irradiation of the tumor mass with light of a specific wavelength after a certain time of incubation. Due to preferential accumulation of the photosensitizer in tumor cells, this procedure allows a selective inactivation of the malignant tumor while sparing the surrounding tissue to the greatest extent. These features and requirements make the PDT an attractive therapeutic option for the treatment of retinoblastoma, especially when surgical enucleation is a curative option. This extreme solution is still in use in case of tumours that are resistant to conventional chemotherapy or handled too late due to poor access to medical care in less advanced country. In this study we initially conducted in-vitro investigations of the new cationic water-soluble photo sensitizer tetrahydroporphyrin-tetratosylat (THPTS) regarding its photodynamic effect on human Rb-1 and Y79 retinoblastoma cells. We were able to show, that neither the incubation with THPTS without following illumination, nor the sole illumination showed a considerable effect on the proliferation of the retinoblastoma cells, whereas the incubation with THPTS combined with following illumination led to a maximal cytotoxic effect on the tumor cells. Moreover the phototoxicity was lower in normal primary cells from retinal pigmented epithelium demonstrating a higher phototoxic effect of THPTS in cancer cells than in this normal retinal cell type. The results at hand form an encouraging foundation for further in-vivo studies on the therapeutic potential of this promising photosensitizer for the eyeball and vision preserving as well as potentially curative therapy of retinoblastoma.

Retinoblastoma development is a multistep process, and inactivation of the RB1 gene is not sufficient for tumorigenesis. Previous studies suggest that the p53-tumor suppressor is inactivated due to overexpression of p53-antagonists MDM4 and MDM2. This thesis evaluates the importance of ARF, a p53-activator that inhibits MDM2. In retinoblastomas, ARF protein is nearly undetectable despite robust mRNA expression. Chemical inhibition of the proteasome, which regulates ARF protein-turnover, did not result in ARF accumulation in retinoblastoma cells, indicating that ARF protein was not aberrantly degraded by the proteasome. During mouse retinoblastoma development, Arf protein was expressed at low level, and p53-target genes involved in cell cycle arrest and autoregulation were not activated. Overexpression of ARF in retinoblastoma cells led to growth inhibition, accompanied by increased expression of p53 and p53-transcriptional targets. Taken together, our data suggests that low ARF protein is an important factor in silencing of the p53-pathway during retinoblastoma development.

Retinoblastoma development is a multistep process, and inactivation of the RB1 gene is not sufficient for tumorigenesis. Previous studies suggest that the p53-tumor suppressor is inactivated due to overexpression of p53-antagonists MDM4 and MDM2. This thesis evaluates the importance of ARF, a p53-activator that inhibits MDM2. In retinoblastomas, ARF protein is nearly undetectable despite robust mRNA expression. Chemical inhibition of the proteasome, which regulates ARF protein-turnover, did not result in ARF accumulation in retinoblastoma cells, indicating that ARF protein was not aberrantly degraded by the proteasome. During mouse retinoblastoma development, Arf protein was expressed at low level, and p53-target genes involved in cell cycle arrest and autoregulation were not activated. Overexpression of ARF in retinoblastoma cells led to growth inhibition, accompanied by increased expression of p53 and p53-transcriptional targets. Taken together, our data suggests that low ARF protein is an important factor in silencing of the p53-pathway during retinoblastoma development.

SerpinB2 (aka plasminogen activator type 2) is well described as an extracellular inhibitor of urokinase-type plasminogen activator (uPA). However, the majority of SerpinB2 is retained intracellularly, and many uPA-independent activities have been reported for SerpinB2 suggesting an alternate function. This thesis explores the role of SerpinB2 in epithelial tumour cell lines, highlights the problems associated with various expression systems and argues that SerpinB2 has no role in growth or apoptosis of tumour cells. A potential role for immune modulation and angiogenesis is suggested in in vivo models. Previous research using SerpinB2 transfected, clonally selected tumour cell lines suggested that SerpinB2 regulates the retinoblastoma tumour suppressor protein (Rb) by binding and protecting Rb from degradation. Despite the use of two techniques under numerous conditions and positive controls, no significant interaction between SerpinB2 and Rb was found. SerpinB2 was reported to bind Rb through a PENF homology motif located within the SerpinB2 C-D interhelical loop region. The PENF homology motif was postulated to represent the motif responsible for binding to the C-pocket of Rb. Epstein Barr Virus nuclear antigen 6 (EBNA6) is a known Rb binding protein, which contains two predicted PENF homology motifs. However, mutation of the two PENF homology motifs within EBNA6 did not reduce Rb binding. Furthermore, the SerpinB2 PENF homology motif is actually not well conserved between SerpinB2 proteins from multiple species, whereas other regions of the SerpinB2 C-D loop show a high level of conservation. These data do not support a role for SerpinB2 and the PENF homology motif in Rb binding. SerpinB2 has been proposed to have a role in regulating growth and apoptosis. To further investigate this proposed phenotype of SerpinB2, SerpinB2 was expressed in a range of epithelial tumour lines using transient transfection. No change in growth, apoptosis or Rb levels were found. After ≈2-3 month antibiotic selection for the SerpinB2-expressing plasmid, SerpinB2 protein was lost without the loss of the transgene, indicating selective pressure against long-term SerpinB2 protein expression. To further investigate long-term SerpinB2 expression adenovirus and lentivirus vectors were used. Infection of tumour cell lines with adenovirus vectors expressing SerpinB2 resulted in reduced cell growth, characterised by increased p53 (but not Rb) levels and G2 arrest or apoptosis. When SerpinB2 expressing lentivirus vectors were used to transduce the same tumour cell lines, high levels of long-term expression of functional SerpinB2 was achieved. However, SerpinB2-expressing cell lines showed no differences in growth, proliferation, Rb levels, or apoptosis induced by a range of agents. Growth and apoptosis observed with adenovirus SerpinB2 had all the characteristics of adenovirus-associated toxicity, which has been reported previously for specific proteins. These experiments highlighted the problems associated with SerpinB2 expression systems and suggest that SerpinB2 expression per se is not toxic nor has a role in regulating Rb, growth and apoptosis. Screening of a number of tumour cell lines identified the HPV16 transformed cervical cancer line as expressing high levels of SerpinB2. SerpinB2 was located both extracellularly and intracellularly with a cytoplasmic and nuclear distribution. A high molecular weight SerpinB2 species was identified in CaSki cells and was shown to be the N-linked glycosylated species. Sequencing showed the protein to be Type A SerpinB2 and the protein was shown to form an inhibitory complex with uPA. An abundant low molecular weight SerpinB2 species was also identified in CaSki cell supernatants and appeared to be a proteolytic fragment of SerpinB2. Treatment of CaSki with PMA, TNFα and IFNγ increased SerpinB2 levels. Lentiviral based shRNA failed to significantly down regulate SerpinB2 expression and increasing SerpinB2 levels with lentiviral expression did not change growth, apoptosis, Rb levels or E7 transcription. Lentiviral expression of SerpinB2 in (normally SerpinB2 negative) HPV16 transformed SiHa cells, also failed to show changes in Rb levels or E7 transcription. CaSki thus express wild-type and functional SerpinB2, but no evidence could found that SerpinB2 effects HPV16 E7 transcription or Rb levels. The data presented identifies CaSki as valuable source of biologically functional SerpinB2. SerpinB2 expression in breast cancer cells has been associated with positive prognosis. Tubo, a SerpinB2-negative murine breast carcinoma cell line, was transduced with lentivirus expressing SerpinB2 and grown subcutaneously in BALB/c mice. SerpinB2 expressing tumours appeared red and were larger than control tumours. Furthermore, SerpinB2 expressing tumours had a ≈2 fold higher density of blood vessels when compared to Tubo and Tubo expressing EGFP. Mice carrying tumours expressing SerpinB2 also showed reduced anti-tumour IgG2 responses. These data suggest that a role for SerpinB2 in regulating angiogenesis and antitumour immunity. In conclusion, this thesis challenges the notion that SerpinB2 regulates Rb, cell cycle, and apoptosis and suggests a potential role for SerpinB2 in tumour angiogenesis and immunity.