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ORAL 42 - Drug Resistance (ID 160)
- Event: WCLC 2015
- Type: Oral Session
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:R.C. Doebele, J.V. DeGregori
- Coordinates: 9/09/2015, 18:30 - 20:00, Mile High Ballroom 4a-4f
ORAL42.04 - Rictor Alterations Elicit Mechanisms of Survival Advantage and Resistance to Targeted Therapy in Non-Small Cell Lung Cancer (NCSLC) (ID 2991)
18:30 - 20:00 | Author(s): W.K. Hong
Rictor (RPTOR independent companion of MTOR, complex 2) is a highly conserved protein and is a critical component for assembly and functionality of the mTORC2 complex. Alterations of the PI3K/mTOR/AKT pathway are hallmark of many cancer types, underscoring the potential important role of Rictor. The goal of our current study was to characterize the functional consequences of genomic alterations of Rictor in advanced refractory NSCLC. Our preliminary data suggest that Rictor alterations have the potential to, not only signal canonically (via activation of AKT), but also provide cancer cells with alternate, more advantageous oncogenic signaling via non-canonical mechanisms.
We correlated genomic data (DNA next generation sequencing (NGS), Foundation Medicine, Inc) gene expression profiling, and clinical outcome in the context of the ongoing BATTLE-2 clinical trial of targeted therapies in chemo-refractory NSCLC(198 cases). We further (1) surveyed early stage NSCLC cases(230 cases) in The Cancer Genome Atlas (TCGA) database to perform two-way hierarchical clustering comparing gene expression profiling in amplified vs diploid cases; (2) utilized a single-nucleotide polymorphism array to select Rictor amplified and diploid NSCLC cell lines; (3) assessed Rictor protein and RNA expression by Western blot and qRT-PCR, respectively; (4) performed Rictor knockdown (siRNA), and (5) performed drug sensitivity to targeted therapies by MTS assay.
In the Battle-2 cases, we identified 15% of Rictor alterations (9% gene amplifications, 6.6% mutations, non-concomitant). Among the mutations, 1 was mapped to an N-terminal phosphorylation site, while all others are of unknown significance to date. Rictor alterations were significantly associated with lack of 8-week disease control in the AKTi+MEKi therapeutic arm. In the TCGA we found: (1) 10% Rictor amplifications and 3% mutations; (2) significant correlation between amplification and elevated Rictor gene expression; (3) a putative functional gene expression signature associated with Rictor amplification. In diploid cell lines we found concordance between AKT phosphorylation and activation of other downstream mTORC2 targets (i.e. SGK1 and PKCα), but in Rictor amplified cell lines we witnessed a discordant activation of these pathways. Furthermore, following Rictor knockdown in our amplified cell lines, a significant reduction of colony formation, migratory, and invasive potential was seen in a pathway-differential manner. Thus, suggesting that Rictor amplifications may provide survival advantage in select cancer cells by tipping the signaling balance toward a non-canonical oncogenic pathway (AKT-independent[I1] ).Also in a differential pathway manner, Rictor gene amplification and overexpression contributed to resistance to a number of targeted therapies
Rictor alterations may constitute a potential novel mechanism of targeted therapy resistance via the activation of non-canonical signaling pathways. These alterations could define new molecular NSCLC subtypes with distinct biology that expose unique avenues for therapeutic implication. Ongoing studies are exploring therapeutic vulnerabilities, non-canonical signaling and Rictor mutations.
P3.01 - Poster Session/ Treatment of Advanced Diseases – NSCLC (ID 208)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 1
- Coordinates: 9/09/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
P3.01-065 - PET Tumor Response by PERCIST Predicts Local-Regional Control in Locally Advanced NSCLC after Concurrent Chemoradiotherapy with Erlotinib (ID 1242)
09:30 - 17:00 | Author(s): W.K. Hong
Assessing response of locally advanced non-small cell lung cancer (NSCLC) after concurrent chemoradiotherapy by computed tomography (CT) can be complicated by treatment-related pneumonitis or fibrosis. Hypothesizing that measurements of tumor response by F-fluorodeoxyglucose standardized uptake values (SUVs) on positron emission tomography (PET) are more reliably associated with treatment outcomes than those by CT, we compared outcomes and responses according to PET SUV vs. CT among patients in a phase II study of erlotinib+chemoradiation for stage III NSCLC.
Trial 2005-1023 enrolled 46 patients in 2007–2010; patients received 63 Gy in 35 fractions over 7 weeks with daily erlotinib and weekly paclitaxel-carboplatin. Tumor response was assessed on diagnostic CT scans with contrast or CT from PET-CT and scored according to RECIST 1.1. Tumor response was also assessed by PERCIST 1.0 (based on SUV) as follows: complete response (CR), disappearance of all measurable tumors; partial response (PR), ≥30% reduction in the sum of SUVs of target lesions; progressive disease (PD), ≥30% increase in the sum of SUVs of target lesions; and stable disease (SD), insufficient change in SUV to qualify for PR or PD. The longest diameter of measurable primary lesions and the short axis of measurable lymph nodes were measured. All non-target lesions were also measured. Two-sided Pearson’s chi-square tests were used to assess frequency associations. Overall survival (OS) and local-regional control (LRC) rates were assessed from treatment start by Kaplan-Meier analysis and log-rank tests; P≤0.05 indicated significance.
One patient did not have CT and PET after treatment. For the 45 evaluable patients, best response by PET-CT at 6 months after treatment was CR for 15 patients (33%), PR for 19 (42%), SD for 0, PD for 4 (9%), and not available due to did not have baseline or post treatment PET for 7 (16%). Best response by CT at 6 months was CR for 11 (24%), PR for 27 (60), SD for 3 (7%), and PD for 4 (9%) (P<0.001). The 3 patients with SD by CT all died within 7 months after treatment; the 4 patients with PD had new distant metastases. Four-year OS was associated with best overall response on both PET and CT at 6 months (P<0.05) and at 1 year (P<0.05). LRC was associated with best overall response on PET (P<0.01) and best primary tumor response on PET (P<0.05) at 6 and 12 months. Lymph node response was not associated with OS or LRC by PET or CT.
The CR rate was higher with PET than with CT. Tumor response at 6 months by PET or CT predicted treatment outcomes after chemoradiotherapy for stage III NSCLC. The best overall and primary tumor response by PET within 6 months after treatment was more reliably associated with LRC than was response on CT because of difficulty to assess response due to pneumonitis/lung fibrosis.