AbstractCancer, the unregulated proliferation of cells, can occur at any age and may arise from almost all cell types. However, the incidence and types of cancer differ with age. Some cancers are predominantly observed in children, others are mostly restricted to older ages. Treatment strategies of some cancers are very successful and cure is common in childhood, while treatment of the same cancer type is much more challenging in adults. Here, we develop a stochastic model of stem cell proliferation that considers both tissue development and homeostasis and discuss the disturbance of such a system by mutations. Due to changes in population size, mutant fitness becomes context dependent and consequently the effects of mutations on the stem cell population can vary with age. We discuss different mutant phenotypes and show the age dependency of their expected abundances. Most importantly, fitness of particular mutations can change with age and advantageous mutations can become deleterious or vice versa. This perspective can explain unique properties of childhood disorders, for example, the frequently observed phenomenon of a self-limiting leukemia in newborns with trisomy 21, but also explains other puzzling observations such as the increased risk of leukemia in patients with bone marrow failure or chemotherapy induced myelodysplasia.
Reconstructing the in vivo dynamics of hematopoietic stem cells from telomere length distributions
We investigate the in vivo patterns of stem cell divisions in the human hematopoietic system throughout life. In particular, we analyze the shape of telomere length distributions underlying stem cell behavior within individuals. Our mathematical model shows that these distributions contain a fingerprint of the progressive telomere loss and the fraction of symmetric cell proliferations. Our predictions are tested against measured telomere length distributions in humans across all ages, collected from lymphocyte and granulocyte sorted telomere length data of 356 healthy individuals, including 47 cord blood and 28 bone marrow samples. We find an increasing stem cell pool during childhood and adolescence and an approximately maintained stem cell population in adults. Furthermore, our method is able to detect individual differences from a single tissue sample, i.e. a single snapshot. Prospectively, this allows us to compare cell proliferation between individuals and identify abnormal stem cell dynamics, which affects the risk of stem cell related diseases.
Abstract Oncolytic replication competent viruses are increasingly being tested in clinical trials. Their optimal use would be greatly facilitated by technologies that enable repeated and quantitative estimation of the location and population size of the virus as it propagates within the tumor. To address this, we have generated two replication competent measles viruses (MV) that express the thyroidal sodium iodide symporter (NIS) in injected cells. One virus, MV-NIS is in Phase 1 clinical trials and kills cells by formation of syncytia. The second virus, MV-I98A-NIS has a mutation in the MV hemagglutinin protein that prevents syncytium formation and kills cells by lysis. Cells infected with MV-I98A-NIS remain viable for longer compared to MV-NIS and are expected to express higher concentrations of NIS, facilitating in vivo imaging. BxPC-3 human pancreatic carcinoma cells were implanted in the flank of nude mice. Subsequently, the mice were injected with Opti-MEM (control), MV-NIS or MV-I98A-NIS (1x107 TCID50/ml) via the tail vein. On days 3, 5, 8, 10, 12, 15, 17 and 19 after virus injection, mice from the control, and virus injected groups were imaged with SPECT/CT (U-SPECT II) 1 hour after injection of 99mTc. Immediately afterwards, the mice were euthanized, the tumors excised, weighed and isotope activity measured. The tumors were divided into parts for histologic analysis and RNA extraction. NIS gene expression was determined by Q-RT-PCR and immunohistochemistry, while viral genome copy number was determined by Q-RT-PCR for the nucleoprotein (N). Image analysis using ROI was performed using AMIDE with background correction across all imaging planes. There was no correlation between tumor mass (volume) and isotope uptake (R2=0.0001 and 0.0051 for MV-NIS and MV-I98A-Nis respectively) suggesting that isotope uptake was strictly linked to virus infection. There was a strong, linear correlation between the levels of virus dependent NIS expression and isotope activity within the tumor (R2=0.79 and 0.93 for MV-NIS and MV-I98A-NIS respectively). Tumors infected with MV-I98A-NIS had a higher concentration of isotope compared with MV-NIS (p<0.004) and a higher correlation coefficient of NIS isotope uptake versus NIS expression (14.1 mCi/NIS copies/ng RNA versus 11.5, p=0.003), compatible with the observation that tumor cells infected with MV-I98A-NIS remain viable for longer compared to MV-NIS. Activity within tumors increased as a function of time, compatible with ongoing virus replication and spread within the tumors. Correlation of imaging studies with NIS expression and viral genome copy number is ongoing. Our preliminary studies suggest that in vivo imaging can be used to accurately determine the size of the oncolytic virus population within a tumor as a function of time. These observations will be used to understand the dynamics of virus spread within tumors and optimize therapy. Citation Format: Mi-Yeon Jung, Matthew K. Ennis, Chetan P. Offord, David Dingli. Quantitative in vivo imaging of oncolytic virus replication. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4947. doi:10.1158/1538-7445.AM2014-4947
Soluble suppression of tumorigenicity 2 (sST2), but not galactin‐3, adds to prognostication in patients with systemic AL amyloidosis independent of NT‐proBNP and troponin T