Differential p16/INK4A cyclin-dependent kinase inhibitor expression correlates with chemotherapy efficacy in a cohort of 88 malignant pleural mesothelioma patients.

BACKGROUND: Malignant pleural mesothelioma (MPM) is a rare and essentially incurable malignancy most often linked with occupational exposure to asbestos fibres. In common with other malignancies, the development and progression of MPM is associated with extensive dysregulation of cell cycle checkpoint proteins that modulate cell proliferation, apoptosis, DNA repair and senescence. METHODS: The expression of cyclin-dependent kinase inhibitor p16/INK4A was evaluated by immunohistochemistry using tumour biopsy specimens from 88 MPM cases and a semi-quantitative score for p16/INK4A expression was obtained. Post-diagnosis survival and the survival benefit of chemotherapeutic intervention was correlated with p16/INK4A expression. RESULTS: A low, intermediate and high score for p16/INK4A expression was observed for 45 (51.1%), 28 (31.8%) and 15 (17.1%) of the MPM cases, respectively. Those cases with intermediate or high p16/INK4A tumour expression had a significantly better post-diagnosis survival than those cases whose tumours lost p16 expression (log-rank P<0.001). Those patients with sustained p16/INK4A expression who received chemotherapy also had a better survival than those treated patients whose tumours had lost p16/INK4A expression (log-rank P<0.001). CONCLUSIONS: Sustained p16/INK4A expression predicts better post-diagnosis survival in MPM and also better survival following chemotherapeutic intervention.

Aspirin delays mesothelioma growth by inhibiting HMGB1-mediated tumor progression.

High-mobility group box 1 (HMGB1) is an inflammatory molecule that has a critical role in the initiation and progression of malignant mesothelioma (MM). Aspirin (acetylsalicylic acid, ASA) is the most widely used nonsteroidal anti-inflammatory drug that reduces the incidence, metastatic potential and mortality of many inflammation-induced cancers. We hypothesized that ASA may exert anticancer properties in MM by abrogating the carcinogenic effects of HMGB1. Using HMGB1-secreting and -non-secreting human MM cell lines, we determined whether aspirin inhibited the hallmarks of HMGB1-induced MM cell growth in vitro and in vivo. Our data demonstrated that ASA and its metabolite, salicylic acid (SA), inhibit motility, migration, invasion and anchorage-independent colony formation of MM cells via a novel HMGB1-mediated mechanism. ASA/SA, at serum concentrations comparable to those achieved in humans taking therapeutic doses of aspirin, and BoxA, a specific inhibitor of HMGB1, markedly reduced MM growth in xenograft mice and significantly improved survival of treated animals. The effects of ASA and BoxA were cyclooxygenase-2 independent and were not additive, consistent with both acting via inhibition of HMGB1 activity. Our findings provide a rationale for the well documented, yet poorly understood antitumorigenic activity of aspirin, which we show proceeds via HMGB1 inhibition. Moreover, the use of BoxA appears to allow a more efficient HMGB1 targeting while eluding the known gastrointestinal side effects of ASA. Our findings are directly relevant to MM. Given the emerging importance of HMGB1 and its tumor-promoting functions in many cancer types, and of aspirin in cancer prevention and therapy, our investigation is poised to provide broadly applicable information.

Dendrimers bind human serum albumin.

Dendrimers are synthetic, highly branched, spherical macromolecules with nanometer dimensions and potential applications in DNA and drug delivery systems. Human serum albumin (HSA) is a major transporter for delivering several endogenous compounds and drugs in vivo. The aim of this study was to examine the interaction of human serum albumin with several dendrimers such as mPEG-PAMAM (G3), mPEG-PAMAM (G4), and PAMAM (G4) at physiological conditions, using constant protein concentration and various dendrimer compositions. FTIR, UV-visible, CD, and fluorescence spectroscopic methods were used to analyze macromolecule binding mode, the binding constant and the effects of dendrimers complexation on HSA stability and conformation. Structural analysis showed that dendrimers bind HSA via polypeptide polar groups (hydrophilic) with number of bound polymer (n) 1.08 (mPEG-PAMAM-G3), 1.50 (mPEG-PAMAM-G4), and 0.96 (PAMAM-G4). The overall binding constants estimated were of KmPEG-G3=1.3 (+/-0.2)x10(4) M(-1), KmPEG-G4=2.2 (+/-0.4)x10(4) M(-1), and KPAMAM-G4=2.6 (+/-0.5)x10(4) M(-1). HSA conformation was altered by dendrimers with a major reduction of alpha-helix and increase in random coil and turn structures suggesting a partial protein unfolding.

In vivo SCE analysis using bromodeoxyuridine, iododeoxyuridine, and chlorodeoxyuridine.

Sister-chromatid exchange (SCE) frequencies were determined for mouse and rabbit bone-marrow cells following incorporation of 3 different halogenated analogues of thymidine. For both species the SCE frequency was highest for chlorodeoxyuridine, lowest for iododeoxyuridine and intermediate for bromodeoxyuridine. The study demonstrates that halogenated pyrimidine analogues other than brominated compounds can be used for in vivo SCE analysis and that their effects on baseline SCE frequencies are qualitatively similar to results of previous in vitro studies.