PRIMA-1 induces autophagy in cancer cells carrying mutant or wild type p53.

PRIMA-1 is a chemical compound identified as a growth suppressor of tumor cells expressing mutant p53. We previously found that in the MDA-MB-231 cell line expressing high level of the mutant p53-R280K protein, PRIMA-1 induced p53 ubiquitination and degradation associated to cell death. In this study, we investigated the ability of PRIMA-1 to induce autophagy in cancer cells. In MDA-MB-231 and HCT116 cells, expressing mutant or wild type p53, respectively, autophagy occurred following exposure to PRIMA-1, as shown by acridine orange staining, anti-LC3 immunofluorescence and immunoblots, as well as by electron microscopy. Autophagy was triggered also in the derivative cell lines knocked-down for p53, although to a different extent than in the parental cells expressing mutant or wild type p53. In particular, while wild type p53 limited PRIMA-1 induced autophagy, mutant p53 conversely promoted autophagy, thus sustaining cell viability following PRIMA-1 treatment. Therefore, the autophagic potential of PRIMA-1, besides being cell context dependent, could be modulated in a different way by the presence of wild type or mutant p53. Furthermore, since both cell lines lacking p53 were more sensitive to the cytotoxic effect of PRIMA-1 than the parental ones, our findings suggest that a deregulated autophagy may favor cell death induced by this drug

Genetic alterations in astrocytic tumors: hints to a molecular epidemiological interpretation.

General incidence of brain tumors has significantly increased over the past two decades. Although the aetiology of this increase has not been determined, increased life span and improved diagnosis methods can partially be responsible for it. Starting from the epidemiological data on risk factors, we reviewed the molecular events known to be involved in the genesis and progression of the most common brain neoplasm in adult, namely astrocytoma. Alterations in different genes, encoding key regulatory elements in the cell cycle control, were reviewed. In light of the molecular epidemiological notion that carcinogens leave fingerprints, point mutations at the p53 locus from a panel of astrocytic tumor patients from all over the world were analysed. The results of this analysis suggest that the majority of astrocytomas may have a spontaneous origin. In particular, the kind of mutational events observed suggests a major role for mutagenic events occurring at CpG sites. In order to yield valid conclusions on the potential role of environmental mutagenic factors, well designed molecular epidemiological studies on populations clearly showing a higher relative risk of developing brain tumors are needed

6DMAP inhibition of early cell cycle events and induction of mitotic abnormalities

N-6 dimethylaminopurine (6DMAP) has been shown to induce aberrant mitosis in different cell types including Chinese hamster fibroblasts (CHEF/18), The mechanism of action and the cellular targets, however, are still not clear, We showed previously that in CHEF/18 cells this compound inhibits DNA synthesis with a kinetic of inhibition suggestive of an effect on early events of the cell cycle, In this paper we investigated which cellular targets were affected by 6DMAP and found that: (i) the compound inhibits phosphorylation of ribosomal protein S6 and activation of the 70 kDa S6 kinase (p70(S6k)) known to be activated by epidermal growth factor (EGF) in keeping with the notion that it is a protein kinase inhibitor; however the inhibition in vivo appears to be specific as MAP kinase phosphorylation is not inhibited; (ii) 6DMAP drastically affects cytoskeletal components leading to a rapid morphological change in most cells. These data, together with the findings that the dose range and the treatment time effective in inducing the micronuclei containing chromosomes were the same as for DNA synthesis inhibition, suggest that a disturbance in G(1) of signal transduction pathways may contribute to abnormal mitosis