Cervical cancer: An unanticipated consequence of high-risk human papillomavirus infection

Master of ScienceDivision of BiologyNicholas A. WallaceCancer is not a single story, but rather numerous often interwoven tales, each with its own characters and progression. In the case of human papillomavirus (HPV) induced cervical cancer (CaCx), the narrative is about the relationship between virus and host, with the consequences of evolution’s shortsightedness driving the plot. Along with the increased proliferative state characteristic of cancer, cells experience frequent, inaccurate replication and replication stresses (ex. DNA damage and nucleotide starvation). To prevent replication fork stall and collapse generated by these stresses, the cell employs translesion synthesis (TLS). Notably, most of the genes in this pathway are upregulated in CaCx; however, the key protein polymerase eta is not. We have observed that upregulation in this pathway is complicated. It occurs at numerous levels, increasing both mRNA and protein abundance. This research further dissects how TLS upregulation occurs. Data shows that in CaCx-derived cell lines, the stability of some TLS proteins is increased, while the stability of other TLS proteins is unchanged. The increased proliferation, typical of these cell lines, cannot account for the enhanced stability. Despite increased TLS protein stability, these cells fail to adequately activate TLS increasing the risk of DNA damage. Genomic instability is a driving factor in HPV genome integration that prevents viral propagation and leads to cell transformation. It also raises mutagenesis rates, likely creating a selective pressure for tolerating failed TLS. The elevated mutation rate known to be associated with failed TLS could also provide a mechanism for acquired resistance to the drugs commonly used to treat CaCx. Changes in protein abundance are routinely used as biomarkers that can lead to the improved outcomes associated with early cancer detection. Elevated TLS protein could be leveraged to ensure cervical cancers are detected during Stage 1, when the 5-year survival rate is 80-90%, rather than at Stage IV, when the rate dips to around 15%

Three Dimensional Visualization and Fractal Analysis of Mosaic Patches in Rat Chimeras: Cell Assortment in Liver, Adrenal Cortex and Cornea

The production of organ parenchyma in a rapid and reproducible manner is critical to normal development. In chimeras produced by the combination of genetically distinguishable tissues, mosaic patterns of cells derived from the combined genotypes can be visualized. These patterns comprise patches of contiguously similar genotypes and are different in different organs but similar in a given organ from individual to individual. Thus, the processes that produce the patterns are regulated and conserved. We have previously established that mosaic patches in multiple tissues are fractal, consistent with an iterative, recursive growth model with simple stereotypical division rules. Fractal dimensions of various tissues are consistent with algorithmic models in which changing a single variable (e.g. daughter cell placement after division) switches the mosaic pattern from islands to stripes of cells. Here we show that the spiral pattern previously observed in mouse cornea can also be visualized in rat chimeras. While it is generally held that the pattern is induced by stem cell division dynamics, there is an unexplained discrepancy in the speed of cellular migration and the emergence of the pattern. We demonstrate in chimeric rat corneas both island and striped patterns exist depending on the age of the animal. The patches that comprise the pattern are fractal, and the fractal dimension changes with the age of the animal and indicates the constraint in patch complexity as the spiral pattern emerges. The spiral patterns are consistent with a loxodrome. Such data are likely to be relevant to growth and cell division in organ systems and will help in understanding how organ parenchyma are generated and maintained from multipotent stem cell populations located in specific topographical locations within the organ. Ultimately, understanding algorithmic growth is likely to be essential in achieving organ regeneration in vivo or in vitro from stem cell populations.</p

Paracrine sonic hedgehog signalling by prostate cancer cells induces osteoblast differentiation

<p>Abstract</p> <p>Background</p> <p>Sonic hedgehog (Shh) and components of its signalling pathway have been identified in human prostate carcinoma and increased levels of their expression appear to correlate with disease progression and metastasis. The mechanism through which Shh signalling could promote metastasis in bone, the most common site for prostate carcinoma metastasis, has not yet been investigated. The present study determined the effect of Shh signalling between prostate cancer cells and pre-osteoblasts on osteoblast differentiation, a requisite process for new bone formation that characterizes prostate carcinoma metastasis.</p> <p>Results</p> <p>LNCaP human prostate cancer cells modified to overexpress Shh (designated LNShh cells) and MC3T3 mouse pre-osteoblasts were maintained as mixed populations within the same culture chamber. In this non-conventional mixed culture system, LNShh cells upregulated the expression of Shh target genes <it>Gli1 </it>and <it>Patched 1 </it>(<it>Ptc1</it>) in MC3T3 cells and this was inhibited by cyclopamine, a specific chemical inhibitor of hedgehog signalling. Concomitantly, MC3T3 cells exhibited time-dependent decreased cell proliferation, upregulated alkaline phosphatase <it>Akp2 </it>gene expression, and increased alkaline phosphatase activity indicative of early phase osteoblast differentiation. LNShh cell-induced differentiation was inhibited in MC3T3 cells stably transfected with a dominant negative form of Gli1, a transcription factor that mediates Shh signalling. Interestingly, LNShh cells did not significantly increase the endogenous expression of the osteoblast differentiation transcription factor <it>Runx2 </it>and its target genes <it>osteocalcin </it>and <it>osteopontin</it>. Consistent with these results, exogenous Shh peptide did not upregulate <it>Runx2 </it>expression in MC3T3 cells. However, <it>Runx2 </it>levels were increased in MC3T3 cells by ascorbic acid, a known stimulator of osteoblast differentiation.</p> <p>Conclusion</p> <p>Altogether, these data demonstrate that Shh-expressing prostate cancer cells can directly and specifically induce differentiation in pre-osteoblasts via a Gli1-dependent mechanism that does not require transcriptional upregulation of <it>Runx2</it>. Paracrine activation of the Shh pathway in osteoblast progenitors and subsequent induction of osteoblast differentiation could be a mechanism through which high levels of Shh expression in prostate carcinoma contribute to bone metastasis. Targeting of paracrine Shh signalling may provide an effective therapeutic strategy against prostate carcinoma metastasis in bone.</p

GLI1 genotypes do not predict basal cell carcinoma risk: a case control study

<p>Abstract</p> <p>Background</p> <p>Susceptibility to basal cell carcinoma results from complex interactions between ultraviolet radiation exposure and genetic factors. The <it>GLI1 </it>oncogene is believed to play a role in the genesis of these tumors. We determined whether <it>GLI1 </it>polymorphisms were risk factors for developing basal cell carcinoma, either alone or in combination with patterns of past sun exposure, and whether there were functional differences among different <it>GLI1 </it>haplotypes.</p> <p>Results</p> <p><it>GLI1 </it>genotypes at c.2798 and c.3298 from 201 basal cell carcinoma patients were compared to 201 age and sex-matched controls. Neither genotype nor haplotype frequencies differed between cases and controls. However, the odds of developing basal cell carcinoma on the trunk compared to the head/neck appeared somewhat lower with carriers of the c.3298GC than the CC genotype. There was no evidence for interactions between skin type, childhood sunburning, average adult sun exposure, adult sunbathing, or intermittency of sun exposure and <it>GLI1 </it>haplotype. Additionally, we found no significant differences in transcription activation or cell transforming ability among the four <it>GLI1 </it>haplotypes.</p> <p>Conclusion</p> <p>These results suggest that different <it>GLI1 </it>genotypes alone or in combination with past sun exposure patterns as assessed in this study do not affect basal cell carcinoma risk.</p

Three Dimensional Visualization and Fractal Analysis of Mosaic Patches in Rat Chimeras: Cell Assortment in Liver, Adrenal Cortex and Cornea

The production of organ parenchyma in a rapid and reproducible manner is critical to normal development. In chimeras produced by the combination of genetically distinguishable tissues, mosaic patterns of cells derived from the combined genotypes can be visualized. These patterns comprise patches of contiguously similar genotypes and are different in different organs but similar in a given organ from individual to individual. Thus, the processes that produce the patterns are regulated and conserved. We have previously established that mosaic patches in multiple tissues are fractal, consistent with an iterative, recursive growth model with simple stereotypical division rules. Fractal dimensions of various tissues are consistent with algorithmic models in which changing a single variable (e.g. daughter cell placement after division) switches the mosaic pattern from islands to stripes of cells. Here we show that the spiral pattern previously observed in mouse cornea can also be visualized in rat chimeras. While it is generally held that the pattern is induced by stem cell division dynamics, there is an unexplained discrepancy in the speed of cellular migration and the emergence of the pattern. We demonstrate in chimeric rat corneas both island and striped patterns exist depending on the age of the animal. The patches that comprise the pattern are fractal, and the fractal dimension changes with the age of the animal and indicates the constraint in patch complexity as the spiral pattern emerges. The spiral patterns are consistent with a loxodrome. Such data are likely to be relevant to growth and cell division in organ systems and will help in understanding how organ parenchyma are generated and maintained from multipotent stem cell populations located in specific topographical locations within the organ. Ultimately, understanding algorithmic growth is likely to be essential in achieving organ regeneration in vivo or in vitro from stem cell populations

Visualization of Gli Activity in Craniofacial Tissues of Hedgehog-Pathway Reporter Transgenic Zebrafish

The Hedgehog (Hh)-signaling pathway plays a crucial role in the development and maintenance of multiple vertebrate and invertebrate organ systems. Gli transcription factors are regulated by Hh-signaling and act as downstream effectors of the pathway to activate Hh-target genes. Understanding the requirements for Hh-signaling in organisms can be gained by assessing Gli activity in a spatial and temporal fashion.We have generated a Gli-dependent (Gli-d) transgenic line, Tg(Gli-d:mCherry), that allows for rapid and simple detection of Hh-responding cell populations in both live and fixed zebrafish. This transgenic line expresses a mCherry reporter under the control of a Gli responsive promoter, which can be followed by using fluorescent microscopy and in situ hybridization. Expression of the mCherry transgene reporter during embryogenesis and early larval development faithfully replicated known expression domains of Hh-signaling in zebrafish, and abrogating Hh-signaling in transgenic fish resulted in the suppression of reporter expression. Moreover, ectopic shh expression in Tg(Glid:mCherry) fish led to increased transgene production. Using this transgenic line we investigated the nature of Hh-pathway response during early craniofacial development and determined that the neural crest skeletal precursors do not directly respond to Hh-signaling prior to 48 hours post fertilization, suggesting that earlier requirements for pathway activation in this population of facial skeleton precursors are indirect.We have determined that early Hh-signaling requirements in craniofacial development are indirect. We further demonstrate the Tg(Gli-d:mCherry) fish are a highly useful tool for studying Hh-signaling dependent processes during embryogenesis and larval stages