RESUMEN
The dynamics of tumor cell populations is hotly debated: do populations derive hierarchically from a subpopulation of cancer stem cells (CSCs), or are stochastic transitions that mutate differentiated cancer cells to CSCs important? Here we argue that regulation must also be important. We sort human melanoma cells using three distinct cancer stem cell (CSC) markers - CXCR6, CD271 and ABCG2 - and observe that the fraction of non-CSC-marked cells first overshoots to a higher level and then returns to the level of unsorted cells. This clearly indicates that the CSC population is homeostatically regulated. Combining experimental measurements with theoretical modeling and numerical simulations, we show that the population dynamics of cancer cells is associated with a complex miRNA network regulating the Wnt and PI3K pathways. Hence phenotypic switching is not stochastic, but is tightly regulated by the balance between positive and negative cells in the population. Reducing the fraction of CSCs below a threshold triggers massive phenotypic switching, suggesting that a therapeutic strategy based on CSC eradication is unlikely to succeed.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/metabolismo , Melanoma/patología , Proteínas de Neoplasias/metabolismo , Células Madre Neoplásicas/patología , Proteínas del Tejido Nervioso/metabolismo , Receptores de Quimiocina/metabolismo , Receptores de Factor de Crecimiento Nervioso/metabolismo , Receptores Virales/metabolismo , Transportador de Casetes de Unión a ATP, Subfamilia G, Miembro 2 , Humanos , Melanoma/metabolismo , Células Madre Neoplásicas/metabolismo , Fenotipo , Receptores CXCR6RESUMEN
The hyperpolarization-activated I(h) current, coded for by hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, controls synaptic integration and intrinsic excitability in many brain areas. Because of their role in pacemaker function, defective HCN channels are natural candidates for contributing to epileptogenesis. Indeed, I(h) is pathologically altered after experimentally induced seizures, and several independent data indicate a link between dysfunctional HCN channels and different forms of epilepsy. However, direct evidence for functional changes of defective HCN channels correlating with the disease in human patients is still elusive. By screening families with epilepsy for mutations in Hcn1 and Hcn2 genes, we found a recessive loss-of-function point mutation in the gene coding for the HCN2 channel in a patient with sporadic idiopathic generalized epilepsy. Of 17 screened members of the same family, the proband was the only one affected and homozygous for the mutation. The mutation (E515K) is located in the C-linker, a region known to affect channel gating. Functional analysis revealed that homomeric mutant, but not heteromeric wild-type/mutant channels, have a strongly inhibited function caused by a large negative shift of activation range and slowed activation kinetics, effectively abolishing the HCN2 contribution to activity. After transfection into acutely isolated newborn rat cortical neurons, homomeric mutant, but not heteromeric wild type/mutant channels, lowered the threshold of action potential firing and strongly increased cell excitability and firing frequency when compared with wild-type channels. This is the first evidence in humans for a single-point, homozygous loss-of-function mutation in HCN2 potentially associated with generalized epilepsy with recessive inheritance.
Asunto(s)
Epilepsia/genética , Canales Iónicos/genética , Mutación , Neuronas/fisiología , Potenciales de Acción/genética , Adulto , Alelos , Animales , Células Cultivadas , Corteza Cerebral/fisiología , Niño , Epilepsia/metabolismo , Epilepsia/fisiopatología , Humanos , Canales Regulados por Nucleótidos Cíclicos Activados por Hiperpolarización , Activación del Canal Iónico/genética , Canales Iónicos/metabolismo , Masculino , Linaje , Polimorfismo de Nucleótido Simple , Canales de Potasio , Ratas , TransfecciónRESUMEN
We report the results of an attempt to identify the supposed remains of a famous World War I (WWI) Italian soldier who was killed in battle along the Italian front in 1915. Thanks to the availability of offspring from both paternal and maternal lineage Y-STRs and mtDNA were analysed and both showed a clear exclusion scenario: the remains did not belong to the supposed war hero. This is the first effort of identification of the remains of soldiers who perished during World War I within a multidisciplinary project aimed at the retrieval of historical and cultural aspects linked to WWI, and the systematic study of the remains of soldiers and ultimately their identification. This last step involves both Italian and Austrian laboratories.