Resumen: The growth of a cultivated typical brain tumor is studied in this work. The tumor is analyzed both dynamically and morphologically. We have measured its fractal dimension to be d(f) = 1.21 +/- 0.05. From its dynamical behavior we determine the scaling critical exponents of this circular symmetry system which are compatible
with the linear molecular beam epitaxy universality class. A very important feature of tumor profiles is that they are super-rough, which constitutes the first (1 + 1)-dimensional experiment in literature with super-roughness. The results obtained from the dynamics study make manifest two very surprising features of tumor growth: Its dynamics is mainly due to contour cells and the tendency of an interface cell to duplicate is a function of the local curvature. [S0031-9007(98)07545-0].
Resumen: Tumor growth is a surface phenomenon of the molecular beam epitaxy universality class in which diffusion at the surface is the determining factor. This Letter reports experiments performed in mice showing that these dynamics can, however, be changed. By stimulating the immune response, we induced strong neutrophilia around the tumor. The neutrophils hindered
cell surface diffusion so much that they induced new dynamics compatible with the slower quenched-disorder Edwards-Wilkinson universality class. Important clinical effects were also seen, including remarkably high tumor necrosis (around 80%-90% of the tumor), a general increase in survival time [the death ratio in the control group is 15.76 times higher than in the treated group (equivalent to a Cox's model hazard ratio of 0.85; 95% confidence interval 0.76-0.95, p=0.004)], and even the total elimination of some tumors.
Resumen: Scaling techniques were used to analyze the fractal nature of colonies of 15 cell lines growing in vitro as well as of 16 types of tumor developing in vivo. All cell colonies were found to exhibit exactly the same growth dynamics - which correspond to the molecular beam epitaxy (MBE) universality class. MBE dynamics are characterized by
1), a linear growth rate, 2), the constraint of cell proliferation to the colony/tumor border, and 3), surface diffusion of cells at the growing edge. These characteristics were experimentally verified in the studied colonies. That these should show MBE dynamics is in strong contrast with the currently established concept of tumor growth: the kinetics of this type of proliferation rules out exponential or Gompertzian growth. Rather, a clear linear growth regime is followed. The importance of new cell movements - cell diffusion at the tumor border - lies in the fact that tumor growth must be conceived as a competition for space between the tumor and the host, and not for nutrients or other factors. Strong experimental evidence is presented for 16 types of tumor, the growth of which cell surface diffusion may be the main mechanism responsible in vivo. These results explain most of the clinical and biological features of colonies and tumors, offer new theoretical frameworks, and challenge the wisdom of some current clinical strategies.
Resumen: There is evidence that polymorphonuclear neutrophils (PMNs) can exert severe antineoplastic effects. Cross-talk between tumour cells and endothelial cells (ECs) is necessary for the accumulation of PMN around a tumour. This work reports the ability of two PMN-sensitive,
human, permanent cell lines-colorectal adenocarcinoma (HT-29) and pharyngeal squamous-cell carcinoma (FaDu) cells-to act as inflammatory foci. PMNs were cytotoxic to both lines, the adhesion of the PMNs to the tumour cells being important in this effect. The tumour cells released appreciable amounts of IL-8 and GRO alpha, and induced the transmigration of PMN through human microvascular-EC monolayers. Conditioning media associated with both lines induced the adhesion of PMN and the surface expression of ICAM-1 in microvascular-EC. In addition, FaDu-conditioning-medium strongly induced the production of proinflammatory cytokines by microvascular-EC. These results support the idea that tumour cells might normally induce a potent acute inflammatory response, leading to their own destruction.
Resumen: Although the complex and multifactorial process of tumour growth has been extensively studied for decades, our understanding
of the fundamental relationship between tumour growth dynamics and genetic expression profile remains incomplete. Recent studies of tumour dynamics indicate that gene expression in solid tumours would depend on the distance from the centre of the tumour. Since tumour proliferative activity is mainly localised to its external zone, and taking into account that generation and expansion of genetic mutations depend on the number of cell divisions, important differences in gene expression between central and peripheral sections of the same tumour are to be expected. Here, we have studied variations in the genetic expression profile between peripheral and internal samples of the same brain tumour. We have carried out microarray analysis of mRNA expression, and found a differential profile of genetic expression between the two cell subsets. In particular, one major nuclear protein that regulates cell responses to DNA-damaging and stress signals, GADD45 alpha, was expressed at much lower levels in the peripheral zone, as compared to tumour core samples. These differences in GADD45 alpha mRNA transcription levels have been confirmed by quantitative analysis via real time PCR, and protein levels of GADD45 alpha also exhibit the same pattern of differential expression. Our findings suggest that GADD45 alpha might play a major role in the regulation of brain tumour invasive potential.
