Comprehensive genomic profiles of small cell lung cancer

We have sequenced the genomes of 110 small cell lung cancers (SCLC), one of the deadliest human cancers. In nearly all the tumours analysed we found bi-allelic inactivation of TP53 and RB1, sometimes by complex genomic rearrangements. Two tumours with wild-type RB1 had evidence of chromothripsis leading to overexpression of cyclin D1 (encoded by the CCND1 gene), revealing an alternative mechanism of Rb1 deregulation. Thus, loss of the tumour suppressors TP53 and RB1 is obligatory in SCLC. We discovered somatic genomic rearrangements of TP73 that create an oncogenic version of this gene, TP73Dex2/3. In rare cases, SCLC tumours exhibited kinase gene mutations, providing a possible therapeutic opportunity for individual patients. Finally, we observed inactivating mutations in NOTCH family genes in 25% of human SCLC. Accordingly, activation of Notch signalling in a pre-clinical SCLC mouse model strikingly reduced the number of tumours and extended the survival of the mutant mice. Furthermore, neuroendocrine gene expression was abrogated by Notch activity in SCLC cells. This first comprehensive study of somatic genome alterations in SCLC uncovers several key biological processes and identifies candidate therapeutic targets in this highly lethal form of cancer

Expression profiles of SnoN in normal and cancerous human tissues support its tumor suppressor role in human cancer.

SnoN is a negative regulator of TGF-β signaling and also an activator of the tumor suppressor p53 in response to cellular stress. Its role in human cancer is complex and controversial with both pro-oncogenic and anti-oncogenic activities reported. To clarify its role in human cancer and provide clinical relevance to its signaling activities, we examined SnoN expression in normal and cancerous human esophageal, ovarian, pancreatic and breast tissues. In normal tissues, SnoN is expressed in both the epithelium and the surrounding stroma at a moderate level and is predominantly cytoplasmic. SnoN levels in all tumor epithelia examined are lower than or similar to that in the matched normal samples, consistent with its anti-tumorigenic activity in epithelial cells. In contrast, SnoN expression in the stroma is highly upregulated in the infiltrating inflammatory cells in high-grade esophageal and ovarian tumor samples, suggesting that SnoN may potentially promote malignant progression through modulating the tumor microenvironment in these tumor types. The overall levels of SnoN expression in these cancer tissues do not correlate with the p53 status. However, in human cancer cell lines with amplification of the snoN gene, a strong correlation between increased SnoN copy number and inactivation of p53 was detected, suggesting that the tumor suppressor SnoN-p53 pathway must be inactivated, either through downregulation of SnoN or inactivation of p53, in order to allow cancer cell to proliferate and survive. These data strongly suggest that SnoN can function as a tumor suppressor at early stages of tumorigenesis in human cancer tissues

SnoN expression is reduced in pancreatic adenocarcinoma samples.

<p><b>A,</b> Representative SnoN expression in the normal pancreas and in pancreatic adenocarcinoma of varying grades at 20X (top) or 40X (bottom) magnifications. E: epithelium; S: stroma. Green: SnoN; blue, DAPI. <b>B,</b> SnoN staining in normal and pancreatic tumor epithelial cells was quantified using Image J, and the numbers were plotted in the box plot, which includes normal samples (n = 5, mean = 3.08) and pancreatic tumor samples of grade I (n = 21, mean = 1.89), grade II (n = 59, mean = 1.59), and grade III (n = 8, mean = 2.09). SnoN expression in tumor samples was weaker than that in normal pancreatic samples (p = 0.0855 for grade I, p = 0.0125 for II, and p = 0.0518 for III). No significant difference was observed in SnoN epithelial staining between the pancreatic tumor samples. <b>C,</b> SnoN staining in normal (n = 2, mean = 1.87) and tumor stromal samples of grade I (n = 20, mean = 2.10), II (n = 55, mean = 1.70), and III (n = 8, mean = 1.57). There is no statistically significant difference between tumor and normal stroma samples.</p

Elevated SnoN expression correlates with inactivation of p53 in human cancer cell lines but not in primary tumor tissues.

<p><b>A,</b> 914 cancer cell lines from the Novartis CLE were classified based on their p53 gene status (lost or wild-type) as shown in the X-axis and their correlation with the copy numbers of SnoN as indicated in the Y-axis. A significant enrichment of SnoN amplification events in p53 mutant or deleted cell lines was identified (p = 7.25E-009). <b>B,</b> Cell lines from the CLE were divided into 18 different tissue lineages as depicted by various colors, and the correlation between the frequency of TP53 mutation (X-axis) and frequency of SnoN amplification (Y-axis) was determined to be highly significant with a Pearson’s correlation coefficient of 0.7. <b>C,</b> Representative p53 immunohistochemical stain in normal ovarian tissue and ovarian adenocarcinoma of grade I, grade II, and grade III (Original magnification ×20). <b>D,</b> Box plot depicting the intensity of epithelial SnoN expression (Y-axis) and p53 protein levels (as marked from 0 to 5, 0 being the lowest level in normal tissues and 5 being the highest). No significant correlation between the status of SnoN protein level and p53 inactivation was noted as measured by the Kruskal-Wallis test (p = 0.817).</p

A PHASE IIA STUDY REPOSITIONING DESIPRAMINE IN SMALL CELL LUNG CANCER AND OTHER HIGH-GRADE NEUROENDOCRINE TUMORS

BackgroundA bioinformatics approach identified antitumor effects of tricyclic antidepressants (TCAs) in small cell lung cancer (SCLC) and other high-grade neuroendocrine carcinomas (grade 3 neuroendocrine carcinomas) (G3NEC) that was subsequently validated in preclinical models with a putative mechanism of action via inhibition of neuroendocrine signaling pathways. This study was undertaken to reposition the candidate TCA desipramine in a clinical trial in SCLC and G3NEC.MethodsIn this prospective, phase IIa intrapatient dose escalation clinical trial, patients were required to have failed at least one prior chemotherapy for metastatic SCLC or G3NEC. Treatment with desipramine began at 75 mg nightly with escalation in increments of 75 mg weekly to a maximum of 450 mg daily.ResultsSix patients were enrolled, 3 with SCLC, and 3 with G3NEC (lung, rectal, and pancreas). Tolerability of desipramine was worse than predicted. Of the 6 patients enrolled: 1 patient achieved 300 mg daily, 2 patients reached 150 mg daily, 1 patient reached 75 mg daily, and 2 patients were unable to tolerate any stable dose. Reasons for discontinuation included drug-related grade 3 colon pseudo-obstruction, unrelated GI bleed, and grade 1-2 neurocognitive adverse events. Median clinical or radiographic progression free survival was 1.2 months (range 0.2-3.3) and median overall survival from study entry was 2.7 months (range 1.3-5.6).ConclusionsNo clinical or radiographic benefit was observed using desipramine to treat SCLC and G3NEC, so this trial was terminated. Intolerable low and medium grade neurocognitive side effects led to intermittent treatment and early discontinuation in most patients; given this limitation, doses achieved may be inadequate compared to the preclinical studies.MicroabstractA bioinformatics approach previously identified a potential antitumor effect of tricyclic antidepressants (TCAs) in small cell lung cancer (SCLC) and other high-grade neuroendocrine carcinomas (grade 3 neuroendocrine carcinoma) (G3NEC), which was validated in preclinical models. In this prospective, phase IIa clinical trial, patients were required to have failed at least one prior chemotherapy for metastatic SCLC or G3NEC (Ki-67 ≥ 20% or ≥ 20 mitoses/10 HPF). Treatment with desipramine began at 75 mg nightly with escalation by 75 mg weekly to a maximum dose of 450 mg daily. Six patients were enrolled on this clinical trial, 3 with SCLC, and 3 with G3NEC (lung, rectal, and pancreatic). Tolerability of desipramine was worse than predicted. In the 6 patients enrolled: 1 patient achieved 300 mg daily, 2 patients reached 150 mg daily, 1 patient reached 75 mg daily, and 2 patients were unable to tolerate any stable dose. Reasons for discontinuation included drug-related grade 3 colon pseudo-obstruction, unrelated GI bleed, and grade 1-2 drug related dizziness, confusion, and somnolence. Though numbers are small, median clinical or radiographic progression free survival was 1.2 months (range 0.2-3.3) and median overall survival from study entry was 2.7 months (range 1.3-5.6). Although preclinical evidence was promising, no clinical or radiographic benefit was observed using desipramine to treat SCLC and G3NEC, so this trial was terminated

Axon-like protrusions promote small cell lung cancer migration and metastasis.

Metastasis is the main cause of death in cancer patients but remains a poorly understood process. Small cell lung cancer (SCLC) is one of the most lethal and most metastatic cancer types. SCLC cells normally express neuroendocrine and neuronal gene programs but accumulating evidence indicates that these cancer cells become relatively more neuronal and less neuroendocrine as they gain the ability to metastasize. Here we show that mouse and human SCLC cells in culture and in vivo can grow cellular protrusions that resemble axons. The formation of these protrusions is controlled by multiple neuronal factors implicated in axonogenesis, axon guidance, and neuroblast migration. Disruption of these axon-like protrusions impairs cell migration in culture and inhibits metastatic ability in vivo. The co-option of developmental neuronal programs is a novel molecular and cellular mechanism that contributes to the high metastatic ability of SCLC