Ortiz-Cuaran, Mezquita et al.
SUPPLEMENTARY ONLINE CONTENT
METHODS 3 Sample collection 3 Assessment of response to therapy 3 ctDNA sequencing 3 In silico structural modeling 4 RESULTS 6 Patient’s characteristics 6 Patient samples 6 Modifiers of ctDNA detection 7 Concurrent mutations at baseline - cBioPortal 8 Genomic ctDNA profiling at disease progression 9 ctDNA analyses in non-V600E BRAF-mutant NSCLC patients 9 In silico structural modeling 11 SUPPLEMENTARY TABLES 13 Supplementary Table S1: Patients characteristics 13 Supplementary Table S2: Treatment characteristics. 14 Supplementary Table S3: Concurrent alterations found at baseline. 15 Supplementary Table S4: Concurrent alterations found at disease progression on BRAF- targeted therapies. 16 Supplementary Table S5: Uniprot and PDB codes used to analyze the impact of mutation at the protein level. 17 Supplementary Table S6. Genomic alterations reported in the tumor sample at diagnosis for patients presenting concurrent mutations in plasma at baseline. 18 Supplementary Table S7. Genomic alterations reported in the tumor sample at disease progression. 19 Supplementary Table S8: Concurrent ctDNA mutations found in BRAF non-V600E mutant NSCLC patients. 20 Supplementary Table S9: Genomic alterations found at baseline or at disease progression on BRAF-targeted therapies in this study and in other reports in BRAF-mutant melanoma, lung and colorectal cancer. 21 SUPPLEMENTARY FIGURES 23 Supplementary Figure S1: The InVisionFirst®-Lung assay. 23 Supplementary Figure S2: Study flowchart 24 Supplementary Figure S3: Modifiers of ctDNA and BRAF-mutant ctDNA detection in targeted therapy naïve BRAF-driven NSCLC patients. 25
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Supplementary Figure S4: In silico modeling of the concurrent mutations found at baseline. 26 Supplementary Figure S5: Concurrent mutations in BRAF-targeted therapy-naïve, BRAFV600E-mutant NSCLC patients.. 27 Supplementary Figure S6: Longitudinal dynamics of BRAF-mutant ctDNA (%AF) in patient 33 28 Supplementary Figure S7: Impact of BRAF-mutant ctDNA detection at the first-radiological evaluation under BRAF-targeted therapy (n=18). A. P 29 Supplementary Figure S8: Metastatic pattern and BRAF-mutant ctDNA detection at disease progression on targeted therapy in BRAF-driven NSCLC patients. 30 Supplementary Figure S9: Impact of total mutant ctDNA detection at disease progression (PD, n=33) on overall survival (OS). 31 Supplementary Figure S10: Heterogeneous mechanisms of resistance to BRAF-targeted therapies. 32
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METHODS
Sample collection
Samples collected at different time points were classified in three groups for analysis:
1) at time of diagnosis before the start of BRAF-targeted therapy, 2) at time of PD to therapy, with concurrent radiological confirmation of PD, and 3) under treatment response (radiological confirmation of objective response or stable disease).
For the analysis of the sensitivity of the BRAF mutation detection in plasma at diagnosis, we included only the samples collected at time of diagnosis. For the analysis of the resistance mutations, we considered only the samples collected at confirmed progression to BRAF-targeted therapy, concurrent with radiological examination.
Assessment of response to therapy
Systemic response and central nervous system (CNS) response were assessed by body CT scan and by brain CT scan or MRI, respectively, every 2 to 3 months, according to the clinical practice of each center. Systemic and CNS objective response rate (ORR: complete or partial response) and disease control rate (DCR: complete response, partial response or stable disease) were evaluated by RECIST criteria v1.1
1 or per investigator assessment.
ctDNA sequencing
Blood (20 to 30mL) was collected in Ethylenediaminetetraacetic-acid (EDTA) or Cell-
Free DNA BCT® Streck tubes. Blood in Cell-Free DNA BCT® Streck tubes was accepted for processing up to 7 days following collection based on in-house stability
3 Ortiz-Cuaran, Mezquita et al. data. Plasma was isolated using a Standard Operating Procedure and ctDNA quantified by digital PCR (BioRad QX200) targeting a 108bp region of the ribonuclease
P/MRP subunit p30 (RPP30) gene. ctDNA analysis was centralized (Inivata,
Cambridge, UK and Research Triangle Park, US) using InVisionFirst®-Lung, a tagged amplicon-based NGS CGP assay which identifies single nucleotide variants, insertions and deletions, copy number variations and fusions, with whole gene and gene hotspots across a 36-gene panel (Supplementary Figure S1). Briefly, NGS libraries were prepared from 2,000-16,000 amplifiable copies of DNA in a two-step PCR-amplification process, targeting the regions of interest followed by the incorporation of replicate and patient-specific barcodes and Illumina sequencing adapters. Sequencing was performed on the Illumina NextSeq 500 (300 cycle PE) with 5% PhiX. Sequencing files were analyzed using the Inivata Somatic Mutation Analysis (ISoMA) pipeline to identify
SNVs, CNVs and indels. Fusions were not analyzed for this cohort of patients. For the
ISoMA pipeline a minimum Phred quality score of 30 for each base was required for inclusion in the analytics.
In silico structural modeling
Aminoacid sequences of wild-type proteins were recovered from UNIPROT
(http://www.uniprot.org/uniprot/, Supplementary Table S5). The search for homologous sequences and alignment were performed using @TOME-2 server 2, in cases where the 3D structure of the protein or the domain was not available in the
Protein Data Bank (http://www.rcsb.org/). Final models were built using Modeller 7.0 3 and evaluated using the dynamic evolutionary trace as implemented in ViTOusing
@TOME-2 comparative option (Supplementary Table S5). The 3D model or the 3D structure was carefully examined in order to determine the position of the mutation and
4 Ortiz-Cuaran, Mezquita et al. whether this mutation is predicted to have an influence on the folding of each protein.
The mutation was also inspected to visualize the close contact surrounding in the side chain of the amino-acid. Graphical representations of structure-function models were done with Pymol.
Two servers were used to evaluate the protein stability upon the mutation: The first one calculates the stability difference score between the wild-type and mutant protein
4. The server is available at http://structure.bioc.cam.ac.uk/sdm2. The second server,
DynaMut, implements two distinct, well established normal mode approaches, which can be used to analyze and visualize protein dynamics by sampling conformations and assess the impact of mutations on protein dynamics and stability resulting from vibrational entropy changes. DynaMut integrates our graph-based signatures along with normal mode dynamics to generate a consensus prediction of the impact of a mutation on protein stability 5 http://biosig.unimelb.edu.au/dynamut/.
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RESULTS
Patient’s characteristics
Median age at diagnosis was 66 years (range 35-83), gender was balanced, 34% of patients were never-smokers and the majority presented lung adenocarcinoma histology. Thirty-two patients had malignant effusion, and 9 had brain metastases at diagnosis.
The median number of systemic therapies was two, with a maximum of eight. BRAF- targeted therapy was mainly received at second line (62.5% of patients). Two patients withdrawn treatment voluntarily and six patients stopped BRAF-targeted therapy due to undesirable side effects leading acute respiratory failure (4 on vemurafenib and 2 on dabrafenib plus trametinib). Thus, the potential impact of the concurrent alterations in the time and response to subsequent treatment could not be evaluated in these patients. Four out of the six non-V600E BRAF-mutant patients were treated with first- line platinum-based chemotherapy with median time of treatment of 2.5 months (range
2.2 – 2.8).
Patient samples
At baseline, thirty-two (68%) samples were collected at disease progression to first- line chemotherapy, immunotherapy or radiotherapy (one case: oligometastatic recurrence disease under dabrafenib, with a unique metastatic axillary lymph node that was resected, the patient then continued BRAF therapy combining dabrafenib + trametinib). Patients 35, 68 and 72 had plasma samples collected at two different time
6 Ortiz-Cuaran, Mezquita et al. points before targeted therapy, resulting in a total of 47 plasma samples collected at baseline.
Modifiers of ctDNA detection
We compared the prevalence of metastatic sites from patients who presented positive or undetectable levels of the BRAF mutation in plasma.
At baseline, in patients with brain metastases, BRAF ctDNA or total mutant ctDNA were not optimally represented in plasma (Supplementary Fig. S3A). Yet, detection of a BRAF mutation in plasma was associated with the presence of liver metastasis:
7% in positive BRAF ctDNA vs 0% in undetectable BRAF ctDNA (Supplementary Fig.
S3A). Similar results were observed when we evaluated the median AF detected in plasma (Supplementary Fig. S3B). Patients with detectable BRAF-mutant ctDNA presented mostly with systemic disease (Supplementary Fig. S3C) and more than two metastatic sites (Supplementary Fig. S3D), compared to patients with undetectable BRAF mutations in plasma. Baseline BRAF-TT samples were collected at disease progression on chemotherapy or immunotherapy (n=32) or before any treatment (n=17). Of note, pretreatment with chemotherapy or immunotherapy in
BRAF-TT naïve patients did not have an impact on the detection of BRAF ctDNA, compared to patients who did not receive any treatment (Supplementary Fig. S3E).
Of note, although the number of patients in this subgroup analysis is small, we observed that alterations in the MAPK, PI3K, receptor tyrosine kinases or signal transducers most likely occurred in patients who received systemic treatment before
BRAF-targeted therapy, compared to treatment-naïve patients (Supplementary Fig.
S3F).
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At disease progression on BRAF-targeted therapy, detectable levels of circulating
BRAFV600E at PD were associated the presence of liver metastasis (Supplementary
Fig. S8A) and the number of metastatic sites (Supplementary Fig. S8B, P = 0.032).
However, the number of previous treatment lines (Supplementary Fig. S8C) did not have an impact on the detection of BRAF mutations in plasma at PD.
Concurrent mutations at baseline - cBioPortal
We compared the frequency of concurrent mutations found in BRAFV600E-mutant patients at baseline, with that reported in 16 studies in the cBioportal (n= 29 patients,
Supplementary Fig. S5). We identified a similar percentage of mutated samples for alterations in CDKN2A, IDH1, PIK3CA TP53 and U2AF1. However, concurrent alterations in AKT1, CTNNB1, ERBB2 and FGFR2 were only detected in our cohort.
Interestingly, our cohort presented 13% of STK11 mutant samples, whereas the samples reported in cBioportal did not harbor STK11 mutations. In the cBioportal, other oncogenic or likely oncogenic alterations (Chakravarty et al. 2017) were reported in genes that are not part of the InVisionFirst®-Lung assay: PBRM1 (7%) and SETD2
(38%). Mutations in TP63, TET1, CREBBP, SMAD4, ATM, KMT2C, ARID1A, RARA,
RBM10, KLF5, KMT2D and MGA, were detected in a one case-basis.
Longitudinal dynamics of BRAF –mutant ctDNA under BRAF-targeted therapy
Patient 33 (Supplementary Fig. S6) presented partial response on vemurafenib and presented disease progression in a lung lesion after 3.5 years under vemurafenib.
Subsequent treatment with chemotherapy showed a rapid tumor response at the first- scanographic evaluation. In this patient, longitudinal serial plasma genotyping revealed that circulating levels of BRAFV600E reflected the tumor responses during treatment as
8 Ortiz-Cuaran, Mezquita et al. they were undetectable during partial response, followed by a subsequent rise coincident with disease progression under vemurafenib.
Genomic ctDNA profiling at disease progression
Genomic ctDNA sequencing was performed on 46 plasma samples, collected from 35 patients, at PD on BRAF inhibitor (24 samples) or on the combination of dabrafenib and trametinib (22 samples). Plasma samples were collected at resistance to different lines of BRAF-targeted therapies in patients 55 and 57 and repeated plasma samples were collected at progression on dabrafenib and trametinib for patients 40, 58, 64, 65 and 69. Repeated plasma sampling for the latter patients was performed beyond disease progression, under combination treatment, with the aim of assessing the presence of genomic alterations associated with resistance to the treatment and evidence a potential further selection of resistant clones under treatment.
Further evidence of the clinical value of ctDNA was demonstrated in three patients during longitudinal follow-up under treatment, for whom we identified heterogeneous potential mechanisms of resistance to BRAF-targeted therapies (Supplementary Fig.
S10).
ctDNA analyses in non-V600E BRAF-mutant NSCLC patients
Concurrent alterations at baseline
In two non-V600E BRAF-mutant cases we evidenced the presence of concurrent
NRASQ61K (P38, BRAFG596R) and KRASA146V (P34, BRAFG466V) alterations (Fig. 1A).
The NRASQ61K mutation is reportedly oncogenic (Supplementary Table S3). The
KRASA146V alteration was also detected in the tumor biopsy (P34) and is reported to be
9 Ortiz-Cuaran, Mezquita et al. likely oncogenic, as described in the OncoKB database 6 (Supplementary Table S3).
In silico analyses revealed that this mutation potentially leads to a steric effect by blocking the GTP binding (Supplementary Table S3, Fig. S4E, Supplementary data).
Of note, the N581S, G466V and G596R mutations belong to the recently described
Class 3 of BRAF mutations (Yao et al. 2017). These mutants are sensitive to ERK- mediated feedback and their activation of signaling is RAS-dependent. Furthermore, dysregulation of signaling by these mutants in tumors requires coexistent mechanisms for maintaining RAS activation despite ERK-dependent feedback (Yao et al. 2017). We show that ctDNA profiling evidenced that two of the non-V600E patients presented concurrent mutations in KRAS (P34) and NRAS (P38) (Supplementary Table S8), similar to what was reported in melanoma (Yao et al. 2017). No mutations in receptor tyrosine kinases were detected in ctDNA for these patients. Although preliminary, these observations suggest that genomic analysis of liquid biopsies in non-V600E
NSCLC patients might be a complementary tool to tumor biopsy analyses to determine the effectors of RAS activation in these patients.
Concurrent alterations at disease progression
Genomic analysis of a plasma samples collected from a BRAF G469A mutant patient at PD after 1.9 months of vemurafenib treatment revealed the presence of MET amplification and MYC P246R and U2AF1 S34 alterations beyond the BRAFG469A mutation (Fig. 3A). Amplification of MET and U2AF1 S34 alteration are reported to be oncogenic and likely oncogenic, respectively (OncoKB 6. The molecular impact of the
MYC P246R alteration is currently unknown and in silico structural modeling was not performed since the 3D structure was unavailable (Supplementary Table S3)
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In silico structural modeling
Alterations detected at baseline
FGFR2 A553D (Fig. 1D): This mutation is predicted to have influence in protein stability since it is present in a -sheet in the N-lobe of the protein kinase fold. The side chain of the alanine (non-polar amino-acid) point in non-polar groove form with valine, leucine, methionine and tryptophane residues. The mutation of alanine into aspartate (negative charged amino-acid) is predicted to destabilized the 3D structure of the N-lobe of FGFR2.
PTEN R14K (Fig. 1E): This mutation is predicted to have no influence on the protein stability since this charged side chain is exposed to the solvent. Since this region/position is implicated in the de-ubiquitination of PTEN 7, this mutation potentially up-regulates the function of PTEN.
IDH1 I130T (Supplementary Fig. S4A): This mutation is predicted to have a small influence in protein stability since the environment of the side chain is constituted of non-polar and polar amino-acids (valine, isoleucine, tryptophane, cysteine and glutamine). This residue is located in an allosteric pocket, has a consequence this potentially results in up- or down-regulated the activity of IDH1.
NTRK3 P612T (Supplementary Fig. S4B): This mutation is predicted to have no influence in protein stability since it is present in a loop rich in glycine (flexible residue) in the N-lobe of the protein kinase fold.
Alterations detected at disease progression
PPP2R1A D265G (Fig. 3C, left): This mutation is predicted to have a major effect in protein stability. The aspartate 265 is located onto a -helix and it is implicated in two
11 Ortiz-Cuaran, Mezquita et al. salt bridges with lysines 265 and 304. The mutation of aspartate (negative charged amino-acid) to glycine potentially destabilizes the fold of PPP2R1A and down regulated it is activity.
U2AF1 R156H (Fig. 3C, right): This mutation is predicted to have a strong influence in protein stability since it is present onto a -helix implicated in the zinc finger fold.
The arginine156 is implicated in a salt bridge with glutamate159, which stabilizes the