MYD88 L265P mutations identify a prognostic gene expression signature and a pathway for targeted inhibition in CLL.

The L265P somatic mutation in the Myeloid Differentiation Primary Response 88 (MYD88) gene is a recurrent mutation in chronic lymphocytic leukaemia (CLL). This mutation has functional effects in various haematological malignancies but its role in CLL remains to be fully elucidated. Here, we report that MYD88 L265P mutations are associated with mutated immunoglobulin heavy-chain gene (IGHV-M) status and that among IGHV-M patients, the presence of MYD88 L265P is associated with younger age at diagnosis. Using microarray and RNA-Seq gene expression analysis, we further observe that the MYD88 L265P mutation is associated with a distinctive gene expression signature that predicts both failure-free survival and overall survival. This association was validated in an independent cohort of patients. To determine whether MYD88 L265P mutations can be therapeutically exploited in CLL, we treated primary cells with an inhibitor of interleukin 1 receptor-associated kinase 4 (IRAK4), a critical effector of the MYD88 pathway. IRAK4 inhibition decreased downstream nuclear factor-κB signalling and cell viability in CLL cells, indicating the potential of the MYD88 pathway as a therapeutic target in CLL.

Exome sequencing reveals recurrent germ line variants in patients with familial Waldenström macroglobulinemia.

Familial aggregation of Waldenström macroglobulinemia (WM) cases, and the clustering of B-cell lymphoproliferative disorders among first-degree relatives of WM patients, has been reported. Nevertheless, the possible contribution of inherited susceptibility to familial WM remains unrevealed. We performed whole exome sequencing on germ line DNA obtained from 4 family members in which coinheritance for WM was documented in 3 of them, and screened additional independent 246 cases by using gene-specific mutation sequencing. Among the shared germ line variants, LAPTM5(c403t) and HCLS1(g496a) were the most recurrent, being present in 3/3 affected members of the index family, detected in 8% of the unrelated familial cases, and present in 0.5% of the nonfamilial cases and in <0.05 of a control population. LAPTM5 and HCLS1 appeared as relevant WM candidate genes that characterized familial WM individuals and were also functionally relevant to the tumor clone. These findings highlight potentially novel contributors for the genetic predisposition to familial WM and indicate that LAPTM5(c403t) and HCLS1(g496a) may represent predisposition alleles in patients with familial WM.

Nicotinic acetylcholine receptors mediate lung cancer growth.

Ion channels modulate ion flux across cell membranes, activate signal transduction pathways, and influence cellular transport-vital biological functions that are inexorably linked to cellular processes that go awry during carcinogenesis. Indeed, deregulation of ion channel function has been implicated in cancer-related phenomena such as unrestrained cell proliferation and apoptotic evasion. As the prototype for ligand-gated ion channels, nicotinic acetylcholine receptors (nAChRs) have been extensively studied in the context of neuronal cells but accumulating evidence also indicate a role for nAChRs in carcinogenesis. Recently, variants in the nAChR genes CHRNA3, CHRNA5, and CHRNB4 have been implicated in nicotine dependence and lung cancer susceptibility. Here, we silenced the expression of these three genes to investigate their function in lung cancer. We show that these genes are necessary for the viability of small cell lung carcinomas (SCLC), the most aggressive type of lung cancer. Furthermore, we show that nicotine promotes SCLC cell viability whereas an α3ß4-selective antagonist, α-conotoxin AuIB, inhibits it. Our findings posit a mechanism whereby signaling via α3/α5/ß4-containing nAChRs promotes lung carcinogenesis.

Genomic approaches to chronic lymphocytic leukemia.

This article discusses recent advances in genomic approaches used to understand chronic lymphocytic leukemia. Tools for analyzing DNA-level lesions are described, data obtained from these various platforms summarized, and the clinical relevance of these findings discussed.

Bioluminescence-based high-throughput screen identifies pharmacological agents that target neurotransmitter signaling in small cell lung carcinoma.

BACKGROUND: Frontline treatment of small cell lung carcinoma (SCLC) relies heavily on chemotherapeutic agents and radiation therapy. Though SCLC patients respond well to initial cycles of chemotherapy, they eventually develop resistance. Identification of novel therapies against SCLC is therefore imperative. METHODS AND FINDINGS: We have designed a bioluminescence-based cell viability assay for high-throughput screening of anti-SCLC agents. The assay was first validated via standard pharmacological agents and RNA interference using two human SCLC cell lines. We then utilized the assay in a high-throughput screen using the LOPAC(1280) compound library. The screening identified several drugs that target classic cancer signaling pathways as well as neuroendocrine markers in SCLC. In particular, perturbation of dopaminergic and serotonergic signaling inhibits SCLC cell viability. CONCLUSIONS: The convergence of our pharmacological data with key SCLC pathway components reiterates the importance of neurotransmitter signaling in SCLC etiology and points to possible leads for drug development.

Nicotinic acetylcholine receptor-mediated mechanisms in lung cancer.

Despite the known adverse health effects associated with tobacco use, over 45 million adults in the United States smoke. Cigarette smoking is the major etiologic factor associated with lung cancer. Cigarettes contain thousands of toxic chemicals, many of which are carcinogenic. Nicotine contributes directly to lung carcinogenesis through the activation of nicotinic acetylcholine receptors (nAChRs). nAChRs are ligand-gated ion channels, expressed in both normal and lung cancer cells, which mediate the proliferative, pro-survival, angiogenic, and metastatic effects of nicotine and its nitrosamine derivatives. The underlying molecular mechanisms involve increases in intracellular calcium levels and activation of cancer signal transduction pathways. In addition, acetylcholine (ACh) acts as an autocrine or paracrine growth factor in lung cancer. Other neurotransmitters and neuropeptides also activate similar growth loops. Recent genetic studies further support a role for nAChRs in the development of lung cancer. Several nAChR antagonists have been shown to inhibit lung cancer growth, suggesting that nAChRs may serve as valuable targets for biomarker-guided lung cancer interventions.

Nicotine-mediated activation of dopaminergic neurons in distinct regions of the ventral tegmental area.

Nicotine activation of nicotinic acetylcholine receptors (nAChRs) within the dopaminergic (DAergic) neuron-rich ventral tegmental area (VTA) is necessary and sufficient for nicotine reinforcement. In this study, we show that rewarding doses of nicotine activated VTA DAergic neurons in a region-selective manner, preferentially activating neurons in the posterior VTA (pVTA) but not in the anterior VTA (aVTA) or in the tail VTA (tVTA). Nicotine (1 µM) directly activated pVTA DAergic neurons in adult mouse midbrain slices, but had little effect on DAergic neurons within the aVTA. Quantification of nAChR subunit gene expression revealed that pVTA DAergic neurons expressed higher levels of α4, α6, and ß3 transcripts than did aVTA DAergic neurons. Activation of nAChRs containing the α4 subunit (α4(*) nAChRs) was necessary and sufficient for activation of pVTA DAergic neurons: nicotine failed to activate pVTA DAergic neurons in α4 knockout animals; in contrast, pVTA α4(*) nAChRs were selectively activated by nicotine in mutant mice expressing agonist-hypersensitive α4(*) nAChRs (Leu9'Ala mice). In addition, whole-cell currents induced by nicotine in DAergic neurons were mediated by α4(*) nAChRs and were significantly larger in pVTA neurons than in aVTA neurons. Infusion of an α6(*) nAChR antagonist into the VTA blocked activation of pVTA DAergic neurons in WT mice and in Leu9'Ala mice at nicotine doses, which only activate the mutant receptor indicating that α4 and α6 subunits coassemble to form functional receptors in these neurons. Thus, nicotine selectively activates DAergic neurons within the pVTA through α4α6(*) nAChRs. These receptors represent novel targets for smoking-cessation therapies.

The nicotinic acetylcholine receptor CHRNA5/A3/B4 gene cluster: dual role in nicotine addiction and lung cancer.

More than 1 billion people around the world smoke, with 10 million cigarettes sold every minute. Cigarettes contain thousands of harmful chemicals including the psychoactive compound, nicotine. Nicotine addiction is initiated by the binding of nicotine to nicotinic acetylcholine receptors, ligand-gated cation channels activated by the endogenous neurotransmitter, acetylcholine. These receptors serve as prototypes for all ligand-gated ion channels and have been extensively studied in an attempt to elucidate their role in nicotine addiction. Many of these studies have focused on heteromeric nicotinic acetylcholine receptors containing α4 and ß2 subunits and homomeric nicotinic acetylcholine receptors containing the α7 subunit, two of the most abundant subtypes expressed in the brain. Recently however, a series of linkage analyses, candidate-gene analyses and genome-wide association studies have brought attention to three other members of the nicotinic acetylcholine receptor family: the α5, α3 and ß4 subunits. The genes encoding these subunits lie in a genomic cluster that contains variants associated with increased risk for several diseases including nicotine dependence and lung cancer. The underlying mechanisms for these associations have not yet been elucidated but decades of research on the nicotinic receptor gene family as well as emerging data provide insight on how these receptors may function in pathological states. Here, we review this body of work, focusing on the clustered nicotinic acetylcholine receptor genes and evaluating their role in nicotine addiction and lung cancer.

ASCL1 regulates the expression of the CHRNA5/A3/B4 lung cancer susceptibility locus.

Tobacco contains a variety of carcinogens as well as the addictive compound nicotine. Nicotine addiction begins with the binding of nicotine to its cognate receptor, the nicotinic acetylcholine receptor (nAChR). Genome-wide association studies have implicated the nAChR gene cluster, CHRNA5/A3/B4, in nicotine addiction and lung cancer susceptibility. To further delineate the role of this gene cluster in lung cancer, we examined the expression levels of these three genes as well as other members of the nAChR gene family in lung cancer cell lines and patient samples using quantitative reverse transcription-PCR. Overexpression of the clustered nAChR genes was observed in small-cell lung carcinoma (SCLC), an aggressive form of lung cancer highly associated with cigarette smoking. The overexpression of the genomically clustered genes in SCLC suggests their coordinate regulation. In silico analysis of the promoter regions of these genes revealed putative binding sites in all three promoters for achaete-scute complex homolog 1 (ASCL1), a transcription factor implicated in the pathogenesis of SCLC, raising the possibility that this factor may regulate the expression of the clustered nAChR genes. Consistent with this idea, knockdown of ASCL1 in SCLC, but not in non-SCLC, led to a significant decrease in expression of the alpha 3 and beta 4 genes without having an effect on any other highly expressed nAChR gene. Our data indicate a specific role for ASCL1 in regulating the expression of the CHRNA5/A3/B4 lung cancer susceptibility locus. This regulation may contribute to the predicted role that ASCL1 plays in SCLC tumorigenesis.