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O04 - Molecular Pathology I (ID 126)
- Event: WCLC 2013
- Type: Oral Abstract Session
- Track: Pathology
- Presentations: 1
- Moderators:I.I. Wistuba, W.A. Cooper
- Coordinates: 10/28/2013, 10:30 - 12:00, Parkside Ballroom A, Level 1
O04.01 - Identification of CD74-NRG1, a new recurrent fusion gene in invasive mucinous lung adenocarcinomas of never smokers (ID 4022)
10:30 - 12:00 | Author(s): C.G. Brambilla
Lung adenocarcinoma (AD) of patients who have never smoked frequently bear targetable genome kinase alterations, such as EGFR mutations and translocations affecting ALK, ROS1, and RET genes. These mutations correlate with kinase inhibitor sensitivity in mouse models or in patients. Unfortunately, therapeutically relevant kinase alterations are not present in all lung cancer specimens. Thus, additional genome alterations need to be discovered in order to provide a therapeutic opportunity for the remaining patients.
We collected a cohort of 25 AD specimens of never smokers lacking mutations in KRAS or EGFR, in which we performed transcriptome sequencing with the aim of identifying new oncogenic driver genes.
We were able to identify known kinase fusions affecting ALK, ROS1 and RET genes in 3 cases each. Moreover, we detected one sample carrying a novel chimeric transcript fusing the first six exons of CD74 to the EGF-like domain of the NRG1 III-β3 isoform, leading to the expression of its EGF-like domain in an otherwise NRG1-negative tumor tissue. The fusion gene was further detected in four additional cases out of 94 pan-negative* ADs of never smokers. In total, all 5 cases were identified in stage I invasive mucinous lung adenocarcinomas (IMA) of never smoker females. This tumor type frequently presents with multifocal unresectable disease, for which no effective treatment has been yet established. IMA is highly associated with KRAS mutations; indeed, out of 15 IMA analysed, 6 carried a KRAS mutation (40%), and 4 the CD74-NRG1 fusion (27%). Given the fact that NRG1 signals through ERBB3 and ERBB4 receptors, we aimed to determine which receptor CD74-NRG1 provides the ligand for. We observed that ERBB4 was not expressed in the index case, while ERBB3 was relatively highly expressed and this expression also correlated with a positive phospho-ERBB3 (p-ERBB3) signal in the tumoral tissue of all 5 CD74-NRG1 positive cases. In order to test if this phosphorylation of ERBB3 was statistically significant, we stained a cohort of 241 ADs and found that p-ERBB3 was only positive in 6 of them (p-value<0.0001). Additionally, although both EGFR and ERBB2 were expressed in the index case, only ERBB2 expression correlated with a p-ERBB2 positive signal. These data suggest that CD74-NRG1 might provide the ligand for ERBB3, which may form heterodimers with ERBB2, since ERBB3 is devoid of intrinsic kinase activity and cannot support linear signaling in isolation. This is in line with previous studies showing that NRG1 induces an oncogenic signal through ERBB2-ERBB3 heterodimers engaging the PI3K-AKT pathway. This was further supported by the activation of the PI3K-AKT, but not the MAPK pathway, in CD74-NRG1 transduced H2052 lung cells, after 24h starvation. *pan-negative: EGFR, KRAS, ALK, HER2, BRAF, ROS1 and RET wild-type
Altogether, these data shows that CD74-NRG1 is a new recurrent oncogenic fusion gene, highly associated with IMA of never smokers. It also suggests that CD74-NRG1 fusion protein signals through the ERBB2-ERBB3 receptors complex leading to the activation of the PI3K-AKT pathway, providing a therapeutic opportunity for a tumor type with, so far, no effective treatment.
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P3.02 - Poster Session 3 - Novel Cancer Genes and Pathways (ID 149)
- Event: WCLC 2013
- Type: Poster Session
- Track: Biology
- Presentations: 1
- Coordinates: 10/30/2013, 09:30 - 16:30, Exhibit Hall, Ground Level
P3.02-010 - A PCR-based test detecting ectopic expressions of placenta/germline genes can predict aggressive lung tumours (ID 1648)
09:30 - 16:30 | Author(s): C.G. Brambilla
Cell transformation and tumour progression are associated with severe alterations of the epigenetic control of gene expression. Although the abnormal repression of tumour suppressor genes has been thoroughly investigated, the concept of tissue-specific gene aberrant reactivations in cancer is only starting to emerge. The extent of this process has not been reported yet, mainly because of the difficulties in detecting these expressions by the currently used transcriptomic analyses
We have developed a simple approach, exploiting genome wide expression data, which has enabled us to demonstrate that these "off-context" gene activations occur in any cancer, providing a universal source of cancer biomarkers. By applying this analysis to our series of lung cancer patients (n=297) with the corresponding precise clinical annotations and 5 to 10 years patient follow-up, we found that hundreds of germline-specific genes are ectopically expressed in the tumours and that a subset of 26 genes are specifically activated in a subgroup of highly aggressive metastatic-prone tumours, even at an early stage of the disease. This approach has enabled us to define and isolate a homogeneous group of very aggressive tumours called P3 with at least 3 genes ectopically expressed, independently of other prognosis parameters (histo-pathological or stage) (Rousseaux et al. Sci Transl Med 2013, 5 (186): 186ra66).
Based on these data we setup a PCR based test to directly rank lung tumours by detection of the prognosis associated gene activations. This test was first validated on a series of 60 tumour samples from the same cohort (also analyzed by an affymetrix transcriptomic approach), which revealed the remarkable robustness of the PCR approach and showed a higher sensitivity of the PCR-based detections in tumour ranking. We then extended these PCR-based analyses to include additional patients with precise clinical and pathological annotations and 10 years follow-up but for whom transcriptomic data were not available. Here again we could show that our test successfully ranked the patients into groups with significantly different survival probabilities. we show here the intermediate analysis on a first group of 88 patients without lymph node metastasis treated by surgeryFigure 1
In conclusion we are ready to launch a prospective study based on this PCR test to evaluate its ability to predict tailored follow up of patients after surgery and also tumour sensitivity to design specific targeted therapies including immunotherapy since this ectopic activation may lead to very innovative treatment .