DOCK4 promotes loss of proliferation in glioblastoma progenitor cells through nuclear beta-catenin accumulation and subsequent miR-302-367 cluster expression

Glioblastomas (GBM) are lethal primitive brain tumours characterized by a strong intra-tumour heterogeneity. We observed in GBM tissues the coexistence of functionally divergent micro-territories either enriched in more differentiated and non-mitotic cells or in mitotic undifferentiated OLIG2 positive cells while sharing similar genomic abnormalities. Understanding the formation of such functionally divergent micro-territories in glioblastomas (GBM) is essential to comprehend GBM biogenesis, plasticity and to develop therapies. Here we report an unexpected anti-proliferative role of beta-catenin in non-mitotic differentiated GBM cells. By cell type specific stimulation of miR-302, which directly represses cyclin D1 and stemness features, beta-catenin is capable to change its known proliferative function. Nuclear beta-catenin accumulation in non-mitotic cells is due to a feed forward mechanism between DOCK4 and beta-catenin, allowed by increased GSK3-beta activity. DOCK4 over expression suppresses selfrenewal and tumorigenicity of GBM stem-like cells. Accordingly in the frame of GBM median of survival, increased level of DOCK4 predicts improved patient survival.

ATF3 and p15PAF are novel gatekeepers of genomic integrity upon UV stress

After genotoxic stress, normal cells trigger DNA repair or, if unable to repair, undergo apoptosis to eradicate the cells that bear the risk of becoming tumorigenic. Here we show that repression of the transcription factor, activating transcription factor 3 (ATF3), after ultraviolet (UV)-mediated genotoxic stress impairs the DNA repair process. We provide evidence that ATF3 directly regulates the proliferating cell nuclear antigen (PCNA)-associated factor KIAA0101/p15(PAF). We further show that the expressions of ATF3 and p15(PAF) is sufficient to trigger the DNA repair machinery, and that attenuation of their expression alters DNA repair mechanisms. We show that the expression of p15(PAF) compensates for a lack of ATF3 expression, thereby constituting a major effector of ATF3 in the DNA repair process. In addition, we provide evidence that p15(PAF) expression is required for the correct function of PCNA during DNA repair, as prevention of their interaction significantly alters DNA repair mechanisms. Finally, defective DNA repair, because of the downregulation of p15(PAF) expression, rendered the cells more sensitive to UV-induced cell death. Therefore, our results suggest ATF3 and p15(PAF) as novel gatekeepers of genomic integrity after UV exposure.

[Colon cancer. Study of 153 cases and comparison with a series of 140 historic cases]

The authors study the epidemiological, diagnostic and therapeutic features of 153 consecutive cases of colon cancers collected between 1985 and 1998. They compare the results with those of a previous study performed in the same hospital service (140 cases between 1966 and 1984). It is a series of 79 men and 74 women (sex ratio = 1.07). The mean age was 56.6 +/- 14 years old with 13.7% of the patients who were less than 40 years old. The operability and the resectability were respectively 98.7% and 83.7% with a global operative mortality of 7.9%. According to the Dukes classification, they were 2 A stages, 73 B stages, 32 C stages and 45 D stages. Starting from 1993, 53% of the C stages an 48% of the B stages had an adjuvant chemotherapy. The comparison between our present results and those of our previous series does not show any modification in what regards the mean age, the cancer frequency in young people, the complicated forms proportion and time needed for the diagnosis by comparison to the beginning of symptomatology. The colic cancer prognostic improvement is attained through an earlier diagnosis, making it possible to reduce the developed forms and the complicated forms proportion, the consequence of which is the operative mortality decrease and the log-range survival increase.