Complex Mutations Research Articles

Rare epidermal growth factor receptor gene alterations in non-small cell lung cancer patients, tyrosine kinase inhibitor response and outcome analysis

BackgroundThe predictive value of rare epidermal growth factor receptor gene (EGFR) mutations for non-small cell lung carcinoma (NSCLC) patients remain elusive. We evaluated the distribution, clinicopathological association, tyrosine kinase inhibitor (TKI) response, and outcome of NSCLC patients carrying uncommon EGFR aberrations in comparison to classical EGFR mutations. MethodsTreatment naïve, advanced NSCLC cases tested by Next-Generation sequencing (NGS) method between 2015 and 2020 were included. The objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS) were analyzed. ResultsA total of 237 tumor samples were sequenced. Among the sixty-nine (29%) EGFR mutated cases, 41 (59.4%) harbored classical mutation (37.7% Del19, 21.7% p.L858R). Non-classical aberrations included missense mutations in exon 18/20/21 (15.9%), EGFR amplification (8.7%), exon 20 insertions (7.2%), EGFR Variant III (4.3%), exon 18 indel (2.9%), exon 21 missense (2.9%) and exon 19 missense mutation (1.4%). These occurred as complex mutations in 16% of cases. Oral TKI was administered in 66.7% cases. The patients harboring non-classical variants had a lower ORR and DCR (23.1% and 61.5%) than those carrying a common mutation (57.6% and 84.8%). Collectively, compared to the patients with common EGFR mutations, the uncommon group showed early disease progression and had shorter overall survival. ConclusionNGS testing has the capacity to reveal a diverse spectrum of uncommon EGFR variants. Our study can contribute to the database of uncommon EGFR mutations with a positive influence on evidence-based care of advanced lung cancer patients with EGFR mutations.

Analysis of glucocerebrosidase (GBA) gene mutations in Iranian patients with Gaucher disease.

Objectives:Gaucher disease (GD) is the most common autosomal recessive disorder of glycolipid storage. It results from mutations in the glucocerebrosidase (GBA) gene and leads to GBA deficiency. Different mutations are associated with different phenotypes in the three major types of GD.Materials and Methods:The spectrum of mutations in GBA gene in 26 unrelated patients with GD from different Iranian populations was determined by DNA sequencing, polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP), and amplification-refractory mutation system (ARMS) methods. An in silico analysis was also performed for novel mutations. Results:Six new mutations were identified in this study. The newly detected mutations that could be theoretically harmful included p.I200T (c.599T>C), p.H312D (c.934C>G), p.L325S (c.974T>C), p.L393V (c.1177C>G), p.S439G (c.1315A>G), and p.M455R (c.1365G>A). Also, p.L483P, p.N409S, p.W420X, p.E379K, p.R398Q, p.N227S, p.R202Q, and p.D448H mutations were identified in the patients. Besides, two new complex mutations, namely, p.S439G/p.S439G+p.E379K/- and p.R202Q/p.R202Q+p.N227S/p.N227S, were detected. The most common GBA mutation in the population was p.L483P with an allele frequency of 32.7%, followed by p.N409S (19.2%). Conclusion:The present study detected six new mutations of GBA gene among GD patients. Two mutations (p.L483P and p.N409S) were especially common among Iranians; this finding can be used in implementing screening programs and understanding the molecular basis of GD.

Molecular mechanisms of myeloid malignancies

Almost all genetic abnormalities involved in the occurrence and progression of myelodysplastic syndromes (MDS) and acute myeloid leukemia have been reported within the last decade. The molecular mechanisms of these genetic changes involved in causing dysfunctions in hematopoietic cells have also been clarified in recent years. For MDS, gene mutations of RNA splicing factors and cohesin complex have been shown to trigger not only aberrant RNA splicing or decreased chromatin insulation but also DNA damage response and transcriptional dysregulation through inefficient interaction between promoters and enhancers. Consequently, these newly identified disease-causing mechanisms may be considered potential therapeutic targets.

A tumor-activatable peptide supramolecular nanoplatform for the delivery of dual-gene targeted siRNAs for drug-resistant cancer treatment.

Combinatorial short interference RNA (siRNA) technology for the silencing of multiple genes is expected to provide an effective therapeutic approach for cancer with complex genetic mutation and dysregulation. Herein we present a tumor-activatable supramolecular nanoplatform for the delivery of siRNAs to target telomerase and telomeres for paclitaxel-resistant non-small-cell lung cancer (A549/PTX) treatment. Two different sequences of siRNA are incorporated in a single nanoparticle, which is obtained by self-assembly from a peptide dendrimer. The siRNA stability is improved by the nanoparticle in the presence of serum compared to free siRNA, and these siRNAs are protected from RNA enzyme degradation. In the tumor extracellular acid environment, the PEG corona of the nanoparticle is removed to promote the internalization of siRNAs into tumor cells. The disulfide linkages between the nanoparticle and siRNAs are cleared in the reductive environment of the tumor cells, and the siRNAs are released in the cytoplasm. In vitro experiments show that the gene expression of hTERT and TRF2 at the mRNA and protein levels of A549/PTX tumor cells is down-regulated, which results in cooperative restraining proliferation and invasion of A549/PTX tumor cells. For the tumor cell-targeting function of the MUC1 aptamer and the EPR effect, sufficient tumor accumulation of nanoparticles was observed. Meanwhile, a shift of negative surface charge of nanoparticles to positive charge in the tumor extracellular microenvironment enhances deep penetration of siRNA-incorporating nanoparticles into tumor tissues. In vivo animal studies support that successful down-regulation of hTERT and TRF2 gene expression achieves effective inhibition of the growth and neovascularization of drug-resistant tumor cells. This work has provided a new avenue for drug-resistant cancer treatment by designing and synthesizing a tumor-activatable nanoplatform to achieve the delivery of dual-gene targeted combinatorial siRNAs.

Solving open travelling salesman subset-tour problem through a hybrid genetic algorithm

In open travelling salesman subset-tour problem (OTSSP), the salesman needs to traverse a set of k (≤n) out of n cities and after visiting the last city, the salesman does not necessarily return to the central depot. The goal is to minimize the overall traversal distance of covering k cities. The OTSSP model comprises two types of problems such as subset selection and permutation of the cities. Firstly, the problem of selection takes place as the salesman’s tours do not contain all the cities. On the other hand, the next problem is about to determine the optimal sequence of the cities from the selected subset of cities. To deal with this problem efficiently, a hybrid nearest neighbor technique based crossover-free Genetic algorithm (GA) with complex mutation strategies is proposed. To the best of the author’s knowledge, this is the first hybrid GA for the OTSSP. As there are no existing studies on OTSSP yet, benchmark instances are not available for OTSSP. For computational experiments, a set of test instances is created by using TSPLIB. The extensive computational results show that the proposed algorithm is having great potential in achieving better results for the OTSSP. Our proposed GA being the first evolutionary-based algorithm that will help as the baseline for future research on OTSSP.

TSC/MTOR-mutated eosinophilic renal tumors are a distinct entity that is CK7+/CK20-/vimentin-: a validation study

Unclassified renal cell carcinoma (RCC) accounts for ∼10% of renal tumors, and the most common histologic findingin these cases is eosinophilic cytoplasm. We previously demonstrated that a subset of eosinophilic renal tumors with heterogeneous morphology and immunohistochemical (IHC) staining harbored pathogenic mutations in tuberous sclerosis complex (TSC) or mammalian target of rapamycin (MTOR) as the primary defining mutation. We identified an additional 8 cases of eosinophilic tumors with unusual morphology that were originally diagnosed as chromophobe RCC (CHRCC) or CHRCC, eosinophilic variant. As a comparison, we included four classic CHRCC cases and one CHRCC, eosinophilic variant case. Gross examination revealed solid or solid and cystic patterns. The solid areas were composed of eosinophilic tumor cells divided by congested vessels, whereas the cystic areas were lined by cytologically bland eosinophilic cells with septae containing nests, ribbons, and single eosinophilic tumor cells. The tumor cells had abundant granular eosinophilic cytoplasm with round nuclei and inconspicuous nucleoli. IHC analysis demonstrated diffuse staining for CK7 and negative staining for CK20 and vimentin. Next-generation sequencing identified pathogenic variants in three genes: TSC1, TSC2, and MTOR. They also lacked significant copy number variations in contrast to our control cases. We have demonstrated with our expanded study that cases previously diagnosed as CHRCC or CHRCC, eosinophilic variant with discordant histology and IHC staining patterns may represent a separate subtype of RCC characterized by mutations in the TSC/MTOR pathway.

Polycomb mutant partially suppresses DNA hypomethylation-associated phenotypes in Arabidopsis.

In plants and mammals, DNA methylation and histone H3 lysine 27 trimethylation (H3K27me3), which is deposited by the polycomb repressive complex 2, are considered as two specialized systems for the epigenetic silencing of transposable element (TE) and genes, respectively. Nevertheless, many TE sequences acquire H3K27me3 when DNA methylation is lost. Here, we show in Arabidopsis thaliana that the gain of H3K27me3 observed at hundreds of TEs in the ddm1 mutant defective in the maintenance of DNA methylation, essentially depends on CURLY LEAF (CLF), one of two partially redundant H3K27 methyltransferases active in vegetative tissues. Surprisingly, the complete loss of H3K27me3 in ddm1 clf double mutant plants was not associated with further reactivation of TE expression nor with a burst of transposition. Instead, ddm1 clf plants exhibited less activated TEs, and a chromatin recompaction as well as hypermethylation of linker DNA compared with ddm1 Thus, a mutation in polycomb repressive complex 2 does not aggravate the molecular phenotypes linked to ddm1 but instead partially suppresses them, challenging our assumptions of the relationship between two conserved epigenetic silencing pathways.

SWI/SNF Complex Mutations Promote Thyroid Tumor Progression and Insensitivity to Redifferentiation Therapies.

Mutations of subunits of the SWI/SNF chromatin remodeling complexes occur commonly in cancers of different lineages, including advanced thyroid cancers. Here we show that thyroid-specific loss of Arid1a, Arid2, or Smarcb1 in mouse BRAFV600E-mutant tumors promotes disease progression and decreased survival, associated with lesion-specific effects on chromatin accessibility and differentiation. As compared with normal thyrocytes, BRAFV600E-mutant mouse papillary thyroid cancers have decreased lineage transcription factor expression and accessibility to their target DNA binding sites, leading to impairment of thyroid-differentiated gene expression and radioiodine incorporation, which is rescued by MAPK inhibition. Loss of individual SWI/SNF subunits in BRAF tumors leads to a repressive chromatin state that cannot be reversed by MAPK pathway blockade, rendering them insensitive to its redifferentiation effects. Our results show that SWI/SNF complexes are central to the maintenance of differentiated function in thyroid cancers, and their loss confers radioiodine refractoriness and resistance to MAPK inhibitor-based redifferentiation therapies. SIGNIFICANCE: Reprogramming cancer differentiation confers therapeutic benefit in various disease contexts. Oncogenic BRAF silences genes required for radioiodine responsiveness in thyroid cancer. Mutations in SWI/SNF genes result in loss of chromatin accessibility at thyroid lineage specification genes in BRAF-mutant thyroid tumors, rendering them insensitive to the redifferentiation effects of MAPK blockade.This article is highlighted in the In This Issue feature, p. 995.

DIA-based systems biology approach unveils E3 ubiquitin ligase-dependent responses to a metabolic shift

The yeast Saccharomyces cerevisiae is a powerful model system for systems-wide biology screens and large-scale proteomics methods. Nearly complete proteomics coverage has been achieved owing to advances in mass spectrometry. However, it remains challenging to scale this technology for rapid and high-throughput analysis of the yeast proteome to investigate biological pathways on a global scale. Here we describe a systems biology workflow employing plate-based sample preparation and rapid, single-run, data-independent mass spectrometry analysis (DIA). Our approach is straightforward, easy to implement, and enables quantitative profiling and comparisons of hundreds of nearly complete yeast proteomes in only a few days. We evaluate its capability by characterizing changes in the yeast proteome in response to environmental perturbations, identifying distinct responses to each of them and providing a comprehensive resource of these responses. Apart from rapidly recapitulating previously observed responses, we characterized carbon source-dependent regulation of the GID E3 ligase, an important regulator of cellular metabolism during the switch between gluconeogenic and glycolytic growth conditions. This unveiled regulatory targets of the GID ligase during a metabolic switch. Our comprehensive yeast system readout pinpointed effects of a single deletion or point mutation in the GID complex on the global proteome, allowing the identification and validation of targets of the GID E3 ligase. Moreover, this approach allowed the identification of targets from multiple cellular pathways that display distinct patterns of regulation. Although developed in yeast, rapid whole-proteome-based readouts can serve as comprehensive systems-level assays in all cellular systems.

Whole Exome Sequencing Identifies Cohesin Component STAG1 Mutation in de novo Acute Myeloid Leukemia (FAB M2): A Pilot Study with Cytogenetics, Clinical and Prognostic Implications.

The clinical implications of cohesin gene complex mutation in acute myeloid leukemia (AML) are not well characterized. In the present study, a cohort of 152 de novo unselected adult AML patients underwent conventional and molecular cytogenetic analysis for chromosomal aberrations. Further, we examined the frequency and clinical implications of mutations in cohesin gene complex STAG1, STAG2, RAD21, SMC1, and SMC3 using whole exome sequencing as a pilot study in 10 de novo patients with AML-FAB M2. Among the 10 cases, we identified a functionally heterozygous mutation in exon16 of STAG1 in one patient (10%), however no mutation was observed in STAG2, RAD21, SMC1, and SMC3. Sanger sequencing analysis for exon 16 of STAG1 in the remaining 142 AML cases did not reveal any further mutations, which underlined the observation that mutations took place throughout the cohesin gene complex without presence of a mutational hot spot region. The present study identified a positive correlation between serum bilirubin, LDH, and hematological parameters such as Hb, WBC, and platelet count with STAG1 mutation. Our data suggest that the cohesin complex may represent an attractive therapeutic target for future preclinical and clinical studies. However, more studies with a larger number of patients should be performed prospectively to determine the pathogenic involvement of STAG 1 mutation in AML patients.

Correlation between U2AF1 Gene Mutation Characteristics and Clinical Manifestations and Prognosis in Patients with Myelodysplastic Syndrome

To investigate the correlation between U2AF1 gene mutation and clinical manifestations and prognosis in patients with myelodysplastic syndromes (MDS). The clinical data of 203 MDS patients who accepted Next Generation Sequencing (NGS) was retrospectively analyzed in Nanfang Hospital, Southern Medical University from December 2012 to October 2019. According to whether the patients had U2AF1 gene mutation, the patients were divided into U2AF1 mutated group and non-mutated group, and the relationship between gene mutation characteristics and clinical manifestations and prognosis was analyzed. Then according to the difference of the mutation site of U2AF1, the patients in U2AF1 mutated group were divided into U2AF1S34 mutated group and U2AF1Q157/R156 mutated group, and the correlation between gene mutation characteristics and prognosis was analyzed. The incidence of U2AF1 mutation in MDS patients was approximately 11.3% (23/203), and the mutation frequency of U2AF1 allele was 32.5%. The male ratio in U2AF1 mutated group was significantly higher than that in U2AF1 non-mutated group (P=0.001). There was no patient who had complex karyotypes or TP53 gene mutation in U2AF1 mutated group. There were no significant differences in ages, blood parameters, bone marrow blasts, WHO 2016 classification, IPSS-R category, chromosomal abnormalities like del(5q), -7/del(7q), del(20q), +8, and gene mutation like ASXL1, DNMT3A, RUNX1, SF3B1, and SRSF2 mutation between U2AF1 mutated group and the non-mutated group. Compared with the non-mutated group, there was no significant difference in the overall survival time (P=0.377), the time of acute myeloid leukemia (AML) transformation (P=0.681), and the response rate to hypome- thylating agents in U2AF1 mutated group (P=0.556). Besides, no differences were observed in sex, diagnosis age, WHO 2016 classification, IPSS-R category, blood parameters, overall survival time, and AML transformation time between U2AF1S34 mutated group and U2AF1Q157/R156 mutated group. The U2AF1 gene mutation dose not affect the survival time, AML transformation time, and response rate to hypomethylating agents in MDS patients. Besides, there are no statistical differences in the clinical characteristics and prognosis of MDS patients between U2AF1S34 mutated group and U2AF1Q157/R156 mutated group. Transplantation shows no significant benefit for patients with U2AF1 mutation.

Overcoming TKI resistance in fusion-driven NSCLC: new generation inhibitors and rationale for combination strategies.

During the last several years, multiple gene rearrangements with oncogenic potential have been described in NSCLC, identifying specific clinic-pathological subgroups of patients that benefit from a targeted therapeutic approach, including anaplastic lymphoma kinase (ALK), c-ros protooncogene 1 (ROS1) and, more recently, REarranged during Transfection (RET) and neurotrophic tyrosine receptor kinases (NTRK) genes. Despite initial impressive antitumor activity, the use of targeted therapies in oncogene-addicted NSCLC subgroups is invariably associated with the development of acquired resistance through multiple mechanisms that can include both on-target and off-target mechanisms. However, the process of acquired resistance is a rapidly evolving clinical scenario that constantly evolves under the selective pressure of tyrosine kinase inhibitors. The development of increasingly higher selective and potent inhibitors, traditionally used to overcome resistance to first generation inhibitors, is associated with the development of novel mechanisms of resistance that encompass complex resistance mutations, highly recalcitrant to available TKIs, and bypass track mechanisms. Herein, we provide a comprehensive overview on the therapeutic strategies for overcoming acquired resistance to tyrosine kinase inhibitors (TKIs) targeting the most well-established oncogenic gene fusions in advanced NSCLC, including ALK, ROS1, RET, and NTRK rearrangements.

15886 In silico analysis of gamma-secretase complex mutations in hidradenitis suppurativa demonstrates disease-specific substrate recognition and cleavage alterations

Familial hidradenitis suppurativa and familial Alzheimer disease are both associated with gamma-secretase complex mutations; however, the 2 diseases are not epidemiologically associated. Understanding the molecular differences between the 2 diseases may aid in development of hypotheses for differing pathogenesis and ultimately, targets for detection.

PTEN, ATM, IDH1 mutations and MAPK pathway activation as modulators of PFS and OS in patients treated by first line EGFR TKI, an ancillary study of the French Cooperative Thoracic Intergroup (IFCT) Biomarkers France project

ObjectivesTumor mutation screening is standard of care for patients with stage IV NSCLC. Since a couple of years, widespread NGS approaches used in routine diagnostics to detect driver mutations such as EGFR, KRAS, BRAF or MET allows the identification of other alterations that could modulated the intensity or duration of response to targeted therapies. The prevalence of co-occurring alterations that could affect response or prognosis as not been largely analyzed in clinical settings and large cohorts of patients. Thanks to the IFCT program “Biomarkers France“, a collection of samples and data at a nation-wide level was available to test the impact of co-mutations on first line EGFR TKI in patients with EGFR mutated cancers. Materials and methodsTargeted NGS was assessed on available (n = 208) samples using the Ion AmpliSeq™ Cancer Hotspot Panel v2 to screen for mutations in 50 different cancer genes. ResultsThis study showed that PTEN inactivating mutations, ATM alterations, IDH1 mutations and complex EGFR mutations were predictors of short PFS in patients with a stage 4 lung adenocarcinoma receiving first line EGFR TKI and that PTEN, ATM, IDH1 and KRAS mutations as well as alterations in the MAPK pathway were related to shorter OS. ConclusionThese findings may lead to new treatment options in patients with unfavorable genotypes to optimize first line responses.

Lymphangioleiomyomatosis Association with Underlying Genotype in Patients with Tuberous Sclerosis Complex.

Rationale: Lymphangioleiomyomatosis (LAM) is a female-predominant lung disease caused by mutations in the tuberous sclerosis complex (TSC) genes TSC1 and TSC2.Objectives: To examine the association between TSC mutation subtypes and the prevalence of LAM in women with TSC.Methods: Adult women seen at the Cincinnati Children's Hospital Medical Center's TSC clinic were stratified into the following three groups: those with TSC1 mutation, those with TSC2 mutation, and those with no mutation identified (NMI). Individual TSC manifestations were ascertained by blinded review of chest computed tomographic scans (LAM, multifocal micronodular pneumocyte hyperplasia, and sclerotic bone lesions) and chart review (all other manifestations). The association between mutation status and TSC manifestations was assessed by the Wilcoxon rank-sum test.Results: Our cohort consisted of 55 TSC women, including 30/55 (55%) with TSC2, 12/55 (22%) with TSC1, and 13/55 (23%) with NMI. Twenty-three women (42%) had characteristic cysts consistent with LAM, of whom 16 had TSC2 mutations and seven had NMI. The prevalence of LAM was higher in women with TSC2 mutations compared with women with TSC1 mutations (16/29 [55%] vs. 0/12; P = 0.003). Similarly, renal angiomyolipomas were more common in women with TSC2 mutations compared with women with TSC1 mutations (29/30 [97%] vs. 6/12 [50%]; P = 0.01). There was no association between TSC mutation subtype and the presence of multifocal micronodular pneumocyte hyperplasia, sclerotic bone lesions, and skin or brain involvement. Serum VEGF-D (vascular endothelial growth factor-D) concentrations (median [95% confidence interval]) tended to be higher in patients harboring TSC2 mutations compared with patients with TSC1 mutations (725 pg/ml [612-1,317] vs. 331 pg/ml [284-406]; P = 0.03) and in patients with LAM compared with patients without LAM (725 pg/ml [563-1,609] vs. 429 pg/ml [357-773]; P = 0.02).Conclusions: LAM and angiomyolipomas are more common in women with TSC harboring TSC2 mutations compared with women with TSC1 mutations. Serum VEGF-D is a useful biomarker to suggest the presence of LAM in women with TSC.

MTORC1 activation in lung mesenchyme drives sex- and age-dependent pulmonary structure and function decline

Lymphangioleiomyomatosis (LAM) is a rare fatal cystic lung disease due to bi-allelic inactivating mutations in tuberous sclerosis complex (TSC1/TSC2) genes coding for suppressors of the mechanistic target of rapamycin complex 1 (mTORC1). The origin of LAM cells is still unknown. Here, we profile a LAM lung compared to an age- and sex-matched healthy control lung as a hypothesis-generating approach to identify cell subtypes that are specific to LAM. Our single-cell RNA sequencing (scRNA-seq) analysis reveals novel mesenchymal and transitional alveolar epithelial states unique to LAM lung. This analysis identifies a mesenchymal cell hub coordinating the LAM disease phenotype. Mesenchymal-restricted deletion of Tsc2 in the mouse lung produces a mTORC1-driven pulmonary phenotype, with a progressive disruption of alveolar structure, a decline in pulmonary function, increase of rapamycin-sensitive expression of WNT ligands, and profound female-specific changes in mesenchymal and epithelial lung cell gene expression. Genetic inactivation of WNT signaling reverses age-dependent changes of mTORC1-driven lung phenotype, but WNT activation alone in lung mesenchyme is not sufficient for the development of mouse LAM-like phenotype. The alterations in gene expression are driven by distinctive crosstalk between mesenchymal and epithelial subsets of cells observed in mesenchymal Tsc2-deficient lungs. This study identifies sex- and age-specific gene changes in the mTORC1-activated lung mesenchyme and establishes the importance of the WNT signaling pathway in the mTORC1-driven lung phenotype.

Genomic Analysis of FLT3 Mutations in a Comprehensive NGS Multicenter Study of AML: HM-Screen-Japan 01

Genomic Analysis of FLT3 Mutations in a Comprehensive NGS Multicenter Study of AML: HM-Screen-Japan 01

SF3B1 Splicing Mutation in the Context of Therapy Related MDS

Background: Therapy related myelodysplastic syndromes (t-MDS) account for 10-20% of all myelodysplastic syndromes (MDS). They are associated with poor outcome namely driven by high occurrence of poor risk cytogenetics and TP53 mutations. Acquired SF3B1 splicing mutation is the sole somatic mutation (SM) associated with favorable outcome in de novo MDS and is described among 80% of patients with ring sideroblasts (RS) subytpe. The prognostic value of SF3B1 SM in the context of t-MDS has not been reported. We aimed to compare the outcomes of patients with SF3B1 mutation (mut) between t-MDS and de novo MDS, and the outcome among t-MDS patients harboring SF3B1 mut to those with SF3B1 wild type t-MDS. Patients and Methods: Patients with myelodysplastic syndrome seen at Moffitt Cancer Center between 2013 and 2019 were evaluated and included for analysis. SF3B1 mutational status was assessed via next generation sequencing. We included patients with known SF3B1 status. These patients were further stratified into de novo MDS and those with t-MDS. Further, outcomes of t-MDS patients were evaluated based on SF3B1-mut vs SF3B1-WT. Baseline characteristics were compared by chi square (categorical variables) and t- test (continuous variables). Survival estimates were calculated using the Kaplan-Meier method from date of diagnosis and groups were compared using log-rank test. Multivariate survival analysis performed by means of Cox proportional hazards regression. Results: In a large cohort of patients with myelodysplastic syndrome, 320 patients were identified with SF3B1 SM who were classified as de novo MDS (n=289) and t-MDS (n=31). Baseline characteristics were similar among both groups with t-MDS patients being slightly older and harboring high risk cytogenetics. Mutational distribution was also similar except for CBL which was more observed in t-MDS compared to de novo (10% vs 1%, p-value =.002). AML, transformation rate was 12.5% vs 12.9% for de novo MDS and t-MDS respectively, p-value .943. Median overall survival (OS) in those with de novo MDS SF3B1-mut vs t-MDS SF3B1-mut was 103 months vs 59 months, p-value .001. t-MDS patients were then stratified by wild type SF3B1 (SF3B1-WT) and SF3B1-mut. Of the 272 t-MDS in our database with known SF3B1 status, 31 were SF3B1-mut (11%). Of those with SF3B1-mut, 60% were classified as MDS-RS compared to 4.1% of those SF3B1-wt with t-MDS. Complex cytogenetics were seen in 37.4% vs 10.3% of patients with SF3B1-WT vs SF3B1-mut, p-value .009. TP53 mutation was seen in 36.1% SF3B1-WT vs 10% SF3B1-mut, p-value .004. AML transformation rate was 34.4% in SF3B1-WT compared to 12.9% SF3B1-mut, p-value .016. Median overall survival was17 months in SF3B1-WT vs 43 months in SF3B1-mut, p-value .004. Conclusion: In our study, SF3B1 mutations are more commonly seen in de novo than in therapy related MDS. De novo MDS SF3B1-mut had better outcomes compared to t-MDS SF3B1-mut although rate of AML transformation was similar. In patients with therapy related MDS, those with SF3B1-mut had better outcomes than those with SF3B1-WT. Additionally complex cytogenetics, TP53 mutation, and transformation to AML occurred more with SF3B1-WT than with SF3B1-mut. In the absence of SF3B1 mut, t-MDS with ring sideroblasts has been reported to have higher rate of TP53 mut compared to de novo MDS-RS. To our knowledge, our data is first to suggest that among t-MDS patients, SF3B1-mut may portend a better prognosis. Disclosures Padron: BMS: Research Funding; Novartis: Honoraria; Kura: Research Funding; Incyte: Research Funding. Sallman:Celgene, Jazz Pharma: Research Funding; Agios, Bristol Myers Squibb, Celyad Oncology, Incyte, Intellia Therapeutics, Kite Pharma, Novartis, Syndax: Consultancy. Komrokji:Acceleron: Honoraria; Geron: Honoraria; Agios: Honoraria, Speakers Bureau; AbbVie: Honoraria; JAZZ: Honoraria, Speakers Bureau; Incyte: Honoraria; Novartis: Honoraria; BMS: Honoraria, Speakers Bureau.

Cover Image: Reduced fertility of ISWI mutants in Arabidopsis

ISWI chromatin remodeling complex plays a crucial role in plant development. In this issue, Gu et al. (pp. 1703–1716) report FHA2 as a novel subunit of ISWI complex in Arabidopsis that participates in regulating plant fertility by interacting with RLTs. The cover image shows the reproductive defects caused by the mutation of ISWI complex, which is a consequence of failure in fertilization due to impaired stamen filament elongation.

<p>Case Report: A Metabolic Complete Response to Upfront Osimertinib in a Smoker Non-Small Cell Lung Cancer Patient Harbouring <em>EGFR</em> G719A/V769M Complex Mutation</p>

Complex EGFR mutations are rare in non-small cell lung cancer (NSCLC). Limited clinical evidence is available on the efficacy of EGFR tyrosine kinase inhibitors (TKIs) in patients with NSCLC harbouring these uncommon EGFR mutations. Here, we reported the case of a complete metabolic response in a patient with advanced NSCLC carrying the uncommon EGFR G719A/V769M complex mutation treated with the first-line osimertinib.