Laurence Kheuang

Class III beta-tubulin expression predicts prostate tumor aggressiveness and patient response to docetaxel-based chemotherapy.

Expression of class III β-tubulin (βIII-tubulin) correlates with tumor progression and resistance to taxane-based therapies for several human malignancies, but its use as a biomarker of tumor behavior in prostate cancer (PCa) remains largely unexplored. Here, we describe βIII-tubulin immunohistochemical staining patterns of prostate tumors obtained from a broad spectrum of PCa patients, some of whom subsequently received docetaxel therapy for castration-resistant PCa (CRPC). Elevated βIII-tubulin expression was significantly associated with tumor aggressiveness in PCa patients with presumed localized disease, as it was found to be an independent marker of biochemical recurrence after treatment. Additionally, βIII-tubulin expression in tumor cells was an independent predictor of lower overall survival for patients receiving docetaxel-based chemotherapy for CRPC. Manipulation of βIII-tubulin expression in human PCa cell lines using a human βIII-tubulin expression vector or βIII-tubulin small interfering RNA altered cell survival in response to docetaxel treatment in a manner that supports a role for βIII-tubulin expression as a mediator of PCa cell resistance to docetaxel therapy. Our findings suggest a role for βIII-tubulin as candidate theranostic biomarker to predict the response to docetaxel-based chemotherapy as well as to target for treatment of docetaxel-resistant CRPC.

Hemizygosity of Nf2 is associated with increased susceptibility to asbestos-induced peritoneal tumours

Biallelic NF2 gene inactivation is frequently found in human malignant mesothelioma. In order to assess whether NF2 hemizygosity may enhance susceptibility to asbestos fibres, we investigated the Nf2 status in mesothelioma developed in mice presenting a heterozygous mutation of the Nf2 gene (Nf2KO3/+), after intraperitoneal inoculation of crocidolite fibres. Asbestos-exposed Nf2KO3/+ mice developed tumoural ascites and mesothelioma at a higher frequency than their wild-type (WT) counterparts (P<0.05). Six out of seven mesothelioma cell lines established from neoplastic ascitic fluids of Nf2KO3/+ mice exhibited loss of the WT Nf2 allele and no neurofibromatosis type 2 protein expression was found in these cells. The results show the importance of the NF2 gene in mesothelial oncogenesis, the potential association of asbestos exposure and tumour suppressor gene inactivation, and suggest that NF2 gene mutation may be a susceptibility factor to asbestos.

The NF-κB/IL-6 pathway in metastatic androgen-independent prostate cancer: new therapeutic approaches?

The nuclear factor of kappa beta (NF-κB) transcription factor regulates the transcription of numerous genes including that of interleukin 6 (IL-6). The IL-6 acts as an autocrine and paracrine growth factor of androgen-independent prostate cancer. An aberrant expression of the IL-6 gene and an increase in IL-6 expression are detected in bone metastatic and hormone-refractory prostate cancer. IL-6 has been suggested to have a crucial role in the resistance to chemotherapy or hormonal therapy involving apoptotic cell death. The NF-κB/IL-6 dependent pathways promote tumour-cell survival and in most situations protect cells against apoptotic stimuli. These data provide a rational framework for targeting NF-κB and IL-6 activity in novel biologically based therapies for aggressive and androgen independent prostate cancers.

Increased expression of class III β -tubulin in castration-resistant human prostate cancer

Background:Class III β-tubulin (βIII-tubulin) is expressed in tissues of neuronal lineage and also in several human malignancies, including non-small-cell lung carcinoma, breast and ovarian cancer. Overexpression of βIII-tubulin in these tumours is associated with an unfavourable outcome and resistance to taxane-based therapies. At present, βIII-tubulin expression remains largely uncharacterised in prostate cancer.Methods:In this report, we evaluated the expression of βIII-tubulin in 138 different human prostate tumour specimens by immunohistochemistry from patients with hormone-treated or hormone-untreated prostate cancer. βIII-tubulin expression was also examined in various prostatic cancer cell lines including in androgen-sensitive human prostate cancer cells, LNCaP, grown in androgen-depleted medium in 2D cultures or as tumour xenografts when the host mouse was castrated.Results:Whereas moderate-to-strong βIII-tubulin expression was detected in only 3 out of 74 (4%) hormone-naive tumour specimens obtained from patients who never received hormone therapy, 6 out of 24 tumour specimens (25%) from patients treated for 3 months with neoadjuvant hormone therapy and 24 out of 40 (60%) castration-resistant tumour specimens from chronic hormone-treated patients were found to express significant levels of βIII-tubulin. These findings were supported by in vitro and in vivo settings.Conclusion:Our data indicate that βIII-tubulin expression is augmented in prostate cancer by androgen ablation and that the expression of this β-tubulin isoform is associated with the progression of prostate cancer to the castration-resistant state, a stage largely responsible for mortality from prostate cancer.

Similar tumor suppressor gene alteration profiles in asbestos-induced murine and human mesothelioma.

The status of tumor suppressor genes (TSGs) relevant to human malignant mesothelioma (HMM) pathogenesis was examined in cultures of mesothelioma cells from tumoral ascites developed in mice exposed to asbestos (asb) fibers. The status of the respective hortologous human genes was also investigated in 12 HMM cell cultures. Eleven primary cultures from mice hemizygous for Nƒ2 (asb-Nf2KO3/+) and 4 wild type counterparts (asb-Nf2+/+) were analyzed for mutations in Nf2, p16/Cdkn2a, p19/Arf and Trp53 genes and protein expression of p15/Cdkn2b and Cdk4. TSG alterations in both mouse and human mesothelioma cells consisted in frequent inactivation of p16/Cdkn2a, p19/Arf (or P14/ARF) and p15/Cdkn2b, co-inactivation of p16/Cdkn2a and p15/Cdkn2b and low rate of Trp53 mutations in both asb-Nf2KO3/+ and asb-Nf2+/+ mesothelioma cells. In both mouse and human mesothelioma cells, inactivation of the hortologous genes p16/Cdkn2a or P16/CDKN2A was due to deletions at the Ink4/Arf locus encompassing p19/Arf or P14/ARF, respectively. Loss of heterozygosity at the Nf2 locus was detected in 10 of 11 asb-Nf2KO3/+ cultures and Nf2 gene rearrangement in one asb-Nf2+/+ culture. These data show that the profile of TSG alterations in asbestos-induced mesothelioma is similar in mice and humans. Thus, the mouse mesothelioma model could be useful for human risk assessment, taking into account interindividual variations in genetic sensitivity to carcinogens.

Control of cell cycle progression in human mesothelioma cells treated with gamma interferon

Recombinant human interferon gamma (r-hu-IFNγ) exerts both antitumoral activity in the early stages of human malignant mesothelioma and a cytostatic effect in human mesothelioma (HM) cell lines in vitro. The antiproliferative effect of interferons (IFNs) reported in a variety of cells has been attributed to several mechanisms. In order to progress in the understanding of HM cell growth modulation by r-hu-IFNγ, modifications of cell cycle progression and expression of key cell cycle regulator proteins in response to r-hu-IFNγ were examined. Nine HM cell lines were studied, including one resistant to the antiproliferative effect of r-hu-IFNγ. Except in the resistant cell line r-hu-IFNγ produced an arrest in the G1 and G2-M phases of the cell cycle, associated with a reduction in both cyclin A and cyclin dependent kinase inhibitors (CDKIs) expression. Moreover cyclin B1/cdc2 activity was decreased. The present study provides the first evidence of a G2-arrest in r-hu-IFNγ-treated HM cell lines and indicates that HM cell lines, despite their tumorigenic origin still support cell cycle control. The cell cycle arrest induced by r-hu-IFNγ seems to depend on cyclin regulation through p21WAF1/CIP1- and p27Kip1-independent mechanisms and is not directly related to the induced DNA damage.

BPH gene expression profile associated to prostate gland volume

The aim of the current study was to analyze gene expression profiles in benign prostatic hyperplasia and to compare them with phenotypic properties. Thirty-seven specimens of benign prostatic hyperplasia were obtained from symptomatic patients undergoing surgery. RNA was extracted and hybridized to Affymetrix Chips containing 54,000 gene expression probes. Gene expression profiles were analyzed using cluster, TreeView, and significance analysis of microarrays softwares. In an initial unsupervised analysis, our 37 samples clustered hierarchically in 2 groups of 18 and 19 samples, respectively. Five clinical parameters were statistically different between the 2 groups: in group 1 compared with group 2, patients had larger prostate glands, had higher prostate specific antigen levels, were more likely to be treated by α blockers, to be operated by prostatectomy, and to have major irritative symptoms. The sole independent parameter associated with this dichotome clustering, however, was the prostate gland volume. Therefore, the role of prostate volume was explored in a supervised analysis. Gene expression of prostate glands <60 mL and >60 mL were compared using significance analysis of microarrays and 227 genes were found differentially expressed between the 2 groups (>2 change and false discovery rate of <5%). Several specific pathways including growth factors genes, cell cycle genes, apoptose genes, inflammation genes, and androgen regulated genes, displayed major differences between small and large prostate glands.

Use of mesothelial cell cultures to assess the carcinogenic potency of mineral or man made fibers

Natural mineral fibers may produce pulmonary cancers and mesothelioma. In contrast with lung cancer, the incidence of fiber-induced mesothelioma is not enhanced in smokers compared to non smokers. It is therefore of special interest to use mesothelial cells to study the toxicity of natural or man made mineral fibers. Several years ago, we have developed a method to culture rat pleural mesothelial cells (RPMC). We have first studied the effects of asbestos fibers by the application of in vitro tests formerly developed to determinedthe genotoxicity and transforming potency of soluble xenobiotics. Moreover, we have determined whether RPMC expressed cytochromes P450 known to metabolize polycyclic aromatic hydrocarbons. This paper reviews the results obtained so far. It has been found that asbestos fibers produced a cell transformation and a gentoxicity characterized by the formation of aneuploid cells, abnormal anaphases, chromosomal aberrations and DNA repair (UDS). In addition, RPMC expressed different forms of cytochromes P450. It is nowadays suggested that the tumorigenic potency of asbestos fibers may be related to the fiber dimensions, to their surface properties and in vivo biopersistence; this term involves the fiber solubility in biological medium and the fiber epuration from the lung by clearance mechanisms. Experiments are now in progress to determine whether the in vitro effects are dependent on the fiber parameters suggested as playing a role in the carcinogenic potency.

Occurrence and morphology of tumors induced in nude mice transplanted with chrysotile-transformed rat pleural mesothelial cells

Rat pleural mesothelial cells treated in vitro with chrysotile fibers have been successfully transplanted into nude mice. Three cultures (1 untreated, 2 treated) were injected at passage 75; a fourth culture was obtained from a mesothelioma induced in rat by chrysotile fibers. Overall, tumors grew in each series, but the delay between cell injection and tumor formation was 22 wk with untreated cells whereas only 1 or 2 wk were needed with treated cells, and 1 wk with cells from in vivo‐induced mesothelioma. Pathological study by light and electron microscopy of tumors is reported here nd showed the mesothelial nature of the cells. Comparison between the ultrastructure of the injected cells and tumor cells indicated that the morphology of injected cells was retained in tumors even if the delay in tumor formation was long. These results suggest that this model is useful for investigating mesothelial cell transformation resulting from in vitro or in vivo exposure to certain carcinogens.

Abstract 5472: Class III beta-tubulin in castration resistant human prostate cancer

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC BACKGROUND: Class III β-tubulin (βIII-tubulin) is expressed in tissues of neuronal lineage but it is also expressed in several human malignancies including non small cell lung carcinoma, breast and ovarian cancer. Overexpression of βIII-tubulin in these tumors is associated with an unfavorable outcome and resistance to taxane-based therapies. βIII-tubulin deregulation however is still poorly documented in prostate cancer. Previously, we reported that βIII-tubulin expression is increased in prostate cancer (PCa) cells by androgen ablation. Here we sought to better characterize the contribution of βIII-tubulin to castration resistant PCa, the stage of the tumor most responsible for mortality from PCa. METHODS: βIII-tubulin expression was assayed by immunohistochemistry in prostate tumors obtained from patients with castration resistant PCa. Protein expression was scored as null (0), weak (1), moderate (2) and strong (3) and considered significant when the score was 2 or more in more than 10% of cancer cells. Consecutive sections were also immunostained for neuroendocrine biomarkers, neuron specific enolase (NSE) and chromogranin A (CgA). An androgen independent (AI) variant of LNCaP cells (AI-LNCaP) was assessed for the effects of docetaxel treatment on βIII-tubulin expression. Finally, DU145 cells stably overexpressing βIII-tubulin were tested for their sensitivity to docetaxel relative to control vector-transfected cells. RESULTS: 24/40 specimens of castration resistant tumors were found to express significant levels of βIII-tubulin. In 6 out of 22 cases analyzed, regions of the tumor positively co-stained for both βIII tubulin and NSE, however none of 8 evaluated cases showed co-staining for βIII-tubulin and CgA. AI-LNCaP cells treated with 5 to 10 nM docetaxel showed a time dependent increase in βIII-tubulin expression. DU145 cells stably overexpressing βIII-tubulin were found to be more resistant to docetaxel than the parental counterpart with a 2-fold increase in the IC50. CONCLUSION: Our data indicate that βIII-tubulin is expressed in the majority of castration resistant prostate tumors. Although βIII-tubulin immunostaining of prostate tumor cells sometimes coincides with staining for neuroendocrine markers, most βIII-tubulin positive tumor cells examined did not show coincidental staining so increased βIII-tubulin expression may occur independently of NE differentiation. Regardless, our in vitro studies support a role for βIII-tubulin in the emergence of doxetaxel resistance by androgen independent human PCa cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5472.