Sonic hedgehog (Shh) is a secreted morphogen involved in patterning a wide range of structures in the developing embryo. When cells receive the Shh signal a cascade of effects begin which in turn regulate downstream target genes. The genes controlled by Sonic hedgehog provide messages instructing cells how to differentiate or when to divide. Disruption of the hedgehog signalling cascade leads to a number of developmental disorders and plays a key role in the formation of a range of human cancers. Patched, the receptor for Shh, acts as a tumour suppressor and is mutated in naevoid basal cell carcinoma syndrome (NBCCS). NBCCS patients display a susceptibility to tumour formation, particularly for basal cell carcinoma (BCC). The discovery of Patched mutations in sporadic BCCs and other tumour types further highlights the importance of this pathway to human cancer. The identification of genes regulated by hedgehog is crucial for understanding how disruption of this pathway leads to neoplastic transformation. It is assumed that the abnormal expression of such genes plays a large role in directing cells to divide at inappropriate times. Only a small number of genes controlled by Shh have been described in vertebrate tissues. In the work presented in this thesis a Sonic hedgehog responsive embryonic mouse cell line, C3H/10T1/2, was used as a model system for hedgehog target gene discovery. Known downstream target genes were profiled to determine their induction kinetics, building up a body of knowledge on the response to Shh for this cell type. During this work, it was discovered that C3H/10T1/2 cells do not become fully competent to respond to Shh stimulation until the cells reach a critical density, a factor that had to be taken into account when determining timepoints of interest for further investigation. Several techniques were employed to identify genes that show expression changes between Shh stimulated and control cells. In one of these techniques, RNA from cell cultures activated with Shh was used to interrogate cDNA microarrays, and this provided many insights into the downstream transcriptional consequences of hedgehog stimulation. Microarrays consist of thousands of spots of DNA of known sequence gridded onto glass slides. Experiments using this technology allow the expression level of thousands of genes to be measured simultaneously. Independent stimulation methods combined with northern blotting were used to investigate individual genes of interest, allowing genuine targets to be confirmed and false positives eliminated. This resulted in the identification of eleven target genes. Seven of these are induced by Sonic hedgehog (Thrombomodulin (Thbd), Glucocorticoid induced leucine zipper (Gilz), Brain factor 2 (Bf2), Nuclear receptor subfamily 4, group A, member 1 (Nr4a1), Insulin-like growth factor 2 (Igf2), Peripheral myelin protein 22 (Pmp22), Lim and SH3 Protein 1 (Lasp1)), and four are repressed (Secreted frizzled related proteins 1 and 2 (Sfrp1 and Sfrp2), Macrophage inflammatory protein-1 gamma (Mip-1?), and Anti-mullerian hormone (Amh)). The majority of these represent novel downstream genes not previously reported as targets of Shh. The new target genes have a diverse range of functions, and include transcriptional regulators and molecules known to be involved in regulating cell growth or apoptosis. The corroboration of genes previously implicated in hedgehog signalling, along with the finding of novel targets, demonstrates both the validity and power of the C3H/10T1/2 system for Shh target gene discovery. The identification of novel Sonic hedgehog responsive genes provides candidates whose abnormal expression may be decisive in initiating tumour formation and future studies will investigate their role in development and disease. It is expected that such findings will provide vital clues to the aetiology of various human cancers, and that an understanding of their roles may ultimately provide greater opportunities in the future design of anti-tumour therapies.

Sonic hedgehog (Shh) is a secreted morphogen involved in patterning a wide range of structures in the developing embryo. When cells receive the Shh signal a cascade of effects begin which in turn regulate downstream target genes. The genes controlled by Sonic hedgehog provide messages instructing cells how to differentiate or when to divide. Disruption of the hedgehog signalling cascade leads to a number of developmental disorders and plays a key role in the formation of a range of human cancers. Patched, the receptor for Shh, acts as a tumour suppressor and is mutated in naevoid basal cell carcinoma syndrome (NBCCS). NBCCS patients display a susceptibility to tumour formation, particularly for basal cell carcinoma (BCC). The discovery of Patched mutations in sporadic BCCs and other tumour types further highlights the importance of this pathway to human cancer. The identification of genes regulated by hedgehog is crucial for understanding how disruption of this pathway leads to neoplastic transformation. It is assumed that the abnormal expression of such genes plays a large role in directing cells to divide at inappropriate times. Only a small number of genes controlled by Shh have been described in vertebrate tissues. In the work presented in this thesis a Sonic hedgehog responsive embryonic mouse cell line, C3H/10T1/2, was used as a model system for hedgehog target gene discovery. Known downstream target genes were profiled to determine their induction kinetics, building up a body of knowledge on the response to Shh for this cell type. During this work, it was discovered that C3H/10T1/2 cells do not become fully competent to respond to Shh stimulation until the cells reach a critical density, a factor that had to be taken into account when determining timepoints of interest for further investigation. Several techniques were employed to identify genes that show expression changes between Shh stimulated and control cells. In one of these techniques, RNA from cell cultures activated with Shh was used to interrogate cDNA microarrays, and this provided many insights into the downstream transcriptional consequences of hedgehog stimulation. Microarrays consist of thousands of spots of DNA of known sequence gridded onto glass slides. Experiments using this technology allow the expression level of thousands of genes to be measured simultaneously. Independent stimulation methods combined with northern blotting were used to investigate individual genes of interest, allowing genuine targets to be confirmed and false positives eliminated. This resulted in the identification of eleven target genes. Seven of these are induced by Sonic hedgehog (Thrombomodulin (Thbd), Glucocorticoid induced leucine zipper (Gilz), Brain factor 2 (Bf2), Nuclear receptor subfamily 4, group A, member 1 (Nr4a1), Insulin-like growth factor 2 (Igf2), Peripheral myelin protein 22 (Pmp22), Lim and SH3 Protein 1 (Lasp1)), and four are repressed (Secreted frizzled related proteins 1 and 2 (Sfrp1 and Sfrp2), Macrophage inflammatory protein-1 gamma (Mip-1?), and Anti-mullerian hormone (Amh)). The majority of these represent novel downstream genes not previously reported as targets of Shh. The new target genes have a diverse range of functions, and include transcriptional regulators and molecules known to be involved in regulating cell growth or apoptosis. The corroboration of genes previously implicated in hedgehog signalling, along with the finding of novel targets, demonstrates both the validity and power of the C3H/10T1/2 system for Shh target gene discovery. The identification of novel Sonic hedgehog responsive genes provides candidates whose abnormal expression may be decisive in initiating tumour formation and future studies will investigate their role in development and disease. It is expected that such findings will provide vital clues to the aetiology of various human cancers, and that an understanding of their roles may ultimately provide greater opportunities in the future design of anti-tumour therapies.

Doctor of Philosophy(PhD) / BCC is the commonest cancer in European-derived populations and Australia has the highest recorded incidence in the world, creating enormous individual and societal cost in management of this disease. The incidence of this cancer has been increasing internationally, with evidence of a 1 to 2% rise in incidence in Australia per year over the last two decades. The main four epidemiological risk factors for the development of BCC are ultraviolet radiation (UVR) exposure, increasing age, male sex, and inability to tan. The pattern and timing of UVR exposure is important to BCC risk, with childhood and intermittent UVR exposure both associated with an increased risk. The complex of inherited characteristics making up an individual’s ‘sun sensitivity’ is also important in determining BCC risk. Very little is known about population genetic susceptibility to BCC outside of the rare genodermatosis Gorlin syndrome. Mutations in the tumour suppressor gene patched (PTCH) are responsible for this BCC predisposition syndrome and the molecular pathway and target genes of this highly conserved pathway are well described. Derangments in this pathway occur in sporadic BCC development, and the PTCH gene is an obvious candidate to contribute to non-syndromic susceptibility to BCC. The melanocortin 1 receptor (MC1R) locus is known to be involved in pigmentary traits and the cutaneous response to UVR, and variants have been associated with skin cancer risk. Many other genes have been considered with respect to population BCC risk and include p53, HPV, GSTs, and HLAs. There is preliminary evidence for specific familial aggregation of BCC, but very little known about the causes. 56 individuals who developed BCC under the age of 40 in the year 2000 were recruited from the Skin and Cancer Foundation of Australia’s database. This represents the youngest 7 – 8% of Australians with BCC from a database that captures approximately 10% of Sydney’s BCCs. 212 of their first degree relatives were also recruited, including 89 parents and 123 siblings of these 56 probands. All subjects were interviewed with respect to their cancer history and all reports of cancer verified with histopathological reports where possible. The oldest unaffected sibling for each proband (where available) was designated as an intra-family control. All cases and control siblings filled out a questionnaire regarding their pigmentary and sun sensitivity factors and underwent a skin examination by a trained examiner. Peripheral blood was collected from these cases and controls for genotyping of PTCH. All the exons of PTCH for which mutations have been documented in Gorlin patients were amplified using PCR. PCR products were screened for mutations using dHPLC, and all detectable variants sequenced. Prevalence of BCC and SCC for the Australian population was estimated from incidence data using a novel statistical approach. Familial aggregation of BCC, SCC and MM occurred within the 56 families studied here. The majority of families with aggregation of skin cancer had a combination of SCC and BCC, however nearly one fifth of families in this study had aggregation of BCC to the exclusion of SCC or MM, suggesting that BCCspecific risk factors are also likely to be at work. Skin cancer risks for first-degree relatives of people with early onset BCC were calculated: sisters and mothers of people with early-onset BCC had a 2-fold increased risk of BCC; brothers had a 5-fold increased risk of BCC; and sisters and fathers of people with early-onset BCC had over four times the prevalence of SCC than that expected. For melanoma, the increased risk was significant for male relatives only, with a 10-fold increased risk for brothers of people with early-onset BCC and 3-fold for fathers. On skin examination of cases and controls, several phenotypic factors were significantly associated with BCC risk. These included increasing risk of BCC with having fair, easyburning skin (ie decreasing skin phototype), and with having signs of cumulative sun damage to the skin in the form of actinic keratoses. Signs reflecting the combination of pigmentary characteristics and sun exposure - in the form of arm freckling and solar lentigines - also gave subjects a significantly increased risk BCC. Constitutive red-green reflectance of the skin was associated with decreased risk of BCC, as measured by spectrophotometery. Other non-significant trends were seen that may become significant in larger studies including associations of BCC with propensity to burn, moderate tanning ability and an inability to tan. No convincing trend for risk of BCC was seen with the pigmentary variables of hair or eye colour, and a non-significant reduced risk of BCC was associated with increasing numbers of seborrhoeic keratoses. Twenty PTCH exons (exons 2, 3, 5 to 18, and 20 to 23) were screened, accounting for 97% of the coding regions with published mutations in PTCH. Nine of these 20 exons were found to harbour single nucleotide polymorphisms (SNPs), seen on dHPLC as variant melting curves and confirmed on direct sequencing. SNPs frequencies were not significantly different to published population frequencies, or to Australian general population frequencies where SNP database population data was unavailable. Assuming a Poisson distribution, and having observed no mutations in a sample of 56, we can be 97.5% confident that if there are any PTCH mutations contributing to early-onset BCC in the Australian population, then their prevalence is less than 5.1%. Overall, this study provides evidence that familial aggregation of BCC is occurring, that first-degree relatives are at increased risk of all three types of skin cancer, and that a combination of environmental and genetic risk factors are likely to be responsible. The PTCH gene is excluded as a major cause of this increased susceptibility to BCC in particular and skin cancer in general. The weaknesses of the study design are explored, the possible clinical relevance of the data is examined, and future directions for research into the genetics of basal cell carcinoma are discussed.

Sonic hedgehog (Shh) is a secreted morphogen involved in patterning a wide range of structures in the developing embryo. When cells receive the Shh signal a cascade of effects begin which in turn regulate downstream target genes. The genes controlled by Sonic hedgehog provide messages instructing cells how to differentiate or when to divide. Disruption of the hedgehog signalling cascade leads to a number of developmental disorders and plays a key role in the formation of a range of human cancers. Patched, the receptor for Shh, acts as a tumour suppressor and is mutated in naevoid basal cell carcinoma syndrome (NBCCS). NBCCS patients display a susceptibility to tumour formation, particularly for basal cell carcinoma (BCC). The discovery of Patched mutations in sporadic BCCs and other tumour types further highlights the importance of this pathway to human cancer. The identification of genes regulated by hedgehog is crucial for understanding how disruption of this pathway leads to neoplastic transformation. It is assumed that the abnormal expression of such genes plays a large role in directing cells to divide at inappropriate times. Only a small number of genes controlled by Shh have been described in vertebrate tissues. In the work presented in this thesis a Sonic hedgehog responsive embryonic mouse cell line, C3H/10T1/2, was used as a model system for hedgehog target gene discovery. Known downstream target genes were profiled to determine their induction kinetics, building up a body of knowledge on the response to Shh for this cell type. During this work, it was discovered that C3H/10T1/2 cells do not become fully competent to respond to Shh stimulation until the cells reach a critical density, a factor that had to be taken into account when determining timepoints of interest for further investigation. Several techniques were employed to identify genes that show expression changes between Shh stimulated and control cells. In one of these techniques, RNA from cell cultures activated with Shh was used to interrogate cDNA microarrays, and this provided many insights into the downstream transcriptional consequences of hedgehog stimulation. Microarrays consist of thousands of spots of DNA of known sequence gridded onto glass slides. Experiments using this technology allow the expression level of thousands of genes to be measured simultaneously. Independent stimulation methods combined with northern blotting were used to investigate individual genes of interest, allowing genuine targets to be confirmed and false positives eliminated. This resulted in the identification of eleven target genes. Seven of these are induced by Sonic hedgehog (Thrombomodulin (Thbd), Glucocorticoid induced leucine zipper (Gilz), Brain factor 2 (Bf2), Nuclear receptor subfamily 4, group A, member 1 (Nr4a1), Insulin-like growth factor 2 (Igf2), Peripheral myelin protein 22 (Pmp22), Lim and SH3 Protein 1 (Lasp1)), and four are repressed (Secreted frizzled related proteins 1 and 2 (Sfrp1 and Sfrp2), Macrophage inflammatory protein-1 gamma (Mip-1?), and Anti-mullerian hormone (Amh)). The majority of these represent novel downstream genes not previously reported as targets of Shh. The new target genes have a diverse range of functions, and include transcriptional regulators and molecules known to be involved in regulating cell growth or apoptosis. The corroboration of genes previously implicated in hedgehog signalling, along with the finding of novel targets, demonstrates both the validity and power of the C3H/10T1/2 system for Shh target gene discovery. The identification of novel Sonic hedgehog responsive genes provides candidates whose abnormal expression may be decisive in initiating tumour formation and future studies will investigate their role in development and disease. It is expected that such findings will provide vital clues to the aetiology of various human cancers, and that an understanding of their roles may ultimately provide greater opportunities in the future design of anti-tumour therapies.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Thesis (M.S.)--University of Southern California, 1998. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.P.H.)--University of Texas Health Science Center at Houston, School of Public Health, 2008. / Source: Masters Abstracts International, Volume: 46-05, page: 2666. Adviser: Kathy L. Klos. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (D.Sc.(Odontology))--University of Pretoria, 2003. / "Published work submitted to the University of Pretoria for the degree of Doctor of Science in Odontology (Oral pathology)". Includes bibliographical references. Also available online.

Thesis (M.S.)--University of Southern California, 1998. / Includes bibliographical references.