FLT3-ITD transduces autonomous growth signals during its biosynthetic trafficking in acute myelogenous leukemia cells

FMS-like tyrosine kinase 3 (FLT3) in hematopoietic cells binds to its ligand at the plasma membrane (PM), then transduces growth signals. FLT3 gene alterations that lead the kinase to assume its permanently active form, such as internal tandem duplication (ITD) and D835Y substitution, are found in 30–40% of acute myelogenous leukemia (AML) patients. Thus, drugs for molecular targeting of FLT3 mutants have been developed for the treatment of AML. Several groups have reported that compared with wild-type FLT3 (FLT3-wt), FLT3 mutants are retained in organelles, resulting in low levels of PM localization of the receptor. However, the precise subcellular localization of mutant FLT3 remains unclear, and the relationship between oncogenic signaling and the mislocalization is not completely understood. In this study, we show that in cell lines established from leukemia patients, endogenous FLT3-ITD but not FLT3-wt clearly accumulates in the perinuclear region. Our co-immunofluorescence assays demonstrate that Golgi markers are co-localized with the perinuclear region, indicating that FLT3-ITD mainly localizes to the Golgi region in AML cells. FLT3-ITD biosynthetically traffics to the Golgi apparatus and remains there in a manner dependent on its tyrosine kinase activity. Tyrosine kinase inhibitors, such as quizartinib (AC220) and midostaurin (PKC412), markedly decrease FLT3-ITD retention and increase PM levels of the mutant. FLT3-ITD activates downstream in the endoplasmic reticulum (ER) and the Golgi apparatus during its biosynthetic trafficking. Results of our trafficking inhibitor treatment assays show that FLT3-ITD in the ER activates STAT5, whereas that in the Golgi can cause the activation of AKT and ERK. We provide evidence that FLT3-ITD signals from the early secretory compartments before reaching the PM in AML cells.

Tobacco Use Predicts Unique Mutagenesis Signature in Acute Myelogenous Leukemia

Background: Endogenous and exogenous processes are active in leukemia initiation. Single-base substitution (SBS) data permits aggregation into mutational signatures [MS] with potential for clinical application. Acetaldehyde and Benzo [a] pyrene (BaP) are tobacco mutagens that "drive" signature SBS4 [Catalog of Somatic Mutations in Cancer (COSMIC) https://cancer.sanger.ac.uk/signatures/sbs/] in lung cancer characterized by C>A transversion. This specific MS is associated with favorable response to immune-checkpoint therapy (ICT). Previous epidemiologic data correlate smoking with cancer including leukemia. Tobacco mutagens are ubiquitously distributed in organs once inhaled. However, how mutagenicity develops in hemopoietic stem cell/progenitor is unknown. In this study, our primary objective was to investigate the incidence of MS among patients (pt) diagnosed with Acute Myelogenous Leukemia (AML) with smoking exposure. Methods: After IRB approval, we performed retrospective analysis using the BCM AML database. Data from 58 AML pt was available. For all analysis, current and past smoking were aggregated into "positive exposure". SBSs (C>A, C>G, C>T, T>C, T>G, G>C, G>A, GT and AG) in smokers and never smoker were annotated from ELN 2017 predefined subgroups [i.e. CEBPA, NPM1, P53, ASLX1, RUNX1 and FLT3ITD] and all additional mutations in individual pt. We used descriptive statistics to detect differential clinical predictors for smoking induced MS. Chi-square was used to determine association between SBSs and smoking history. Stepwise logistic regression allowed identification of independent MS that correlated with smoking. Results: Median age for 58 AML pt was 65.5 years [y] (range, 22-89) and 58.3% were male. Smokers were 26/58 (44.8%). Whites, African Americans, Hispanics and Asians comprised 35/60 (58.3%), 7/60 (7.1%), 16/60 (26.6%) and 2/60 (2.3%), respectively. 112 myeloid mutations [91 SBSs, 16 duplications, 16 deletions, and 3 insertions] were recorded. 32/58 (55.1%) had positive smoking exposure. Previous reports suggest that C>A [COSMIC=SBS4], G>C [COSMIC= SBS2 and SBS13] and T>C [COSMIC=SBS5] retain strong smoking association with cancer. However, in addition to C>A [HR=0.10 (0.01-0.6), p=0.02], our logistic model identified G>A, HR=0.12 (0.02-0.4), p=0.002, as predictors of exposure. C>A+G>A MS was observed in 19/25 (76%) of AML pt with smoking exposure, OR=6.56 (1.8-23.9), p=0.002. By ELN-2017 defined subgroups, P53, ASXL1, RUNX1, FLT3 and NPM1 mut were detected in 11/58 (18.9%), 5/58 (8.6%), 4/58 (6.8%), 13/58 (22.4%) and 5/58 (8.6%). RAS was seen in 12/58 (20.6%), IDH 12/58 (20.6%), DNMT3A 10/58 (17.2%) and TET2 7/58 (12%). Interestingly, among smokers exhibiting or not C>A+G>A SBP substitution, P53 was identified in 3/3 (100%) v 0/3 (0%), p=0.05 and RAS in 75% v 25%, p=0.08. Conclusions: Our data suggest that C>A and G>A SBS substitutions are frequently observed in AML pt with smoking exposure. Hemopoietic stem cell/progenitors exposed to smoking products may initiate similar SBSs substitutions as those observed in tobacco induced solid tumors. Previously, lung cancer studies demonstrated that TP53 and KRAS mutations tumors exhibited high rate of C>A transversion associated with tumor-infiltrating lymphocytes (TIL) and high program-death 1 ligand (PD-L1) expression. Further similar studies are needed in adult diagnosed with P53 AML. Figure 1 Figure 1. Disclosures Mims: IDEC: Current holder of individual stocks in a privately-held company; Biogen: Current holder of individual stocks in a privately-held company; Incyte: Research Funding; Pfizer: Research Funding; AVEO: Research Funding; Celgene: Research Funding.

Cardiovascular involvement in blood cancers: ALL, AML, CLL, and CML

Global cancer statistics will continue to grow in the coming years. Leukemia is the fifth leading cause of death in the world and the second one in Iran; therefore, it is very important to study the affected areas, including the cardiovascular system in this disease. In heart cancer, tumors whose primary origin is the heart are called primary tumors, which are very rare. Tumors that originate in other parts of the body and spread to the heart are called secondary tumors. Although heart cancer is still rare, most cancers found in the heart come from other parts of the body and are considered as secondary tumors. The symptoms of metastatic heart cancer vary and depend on the location and extent of the lesion. Cancer can also affect the heart in other ways. One of these ways is the effect of the treatments used, which is reported among acute lymphocytic leukemia, acute myelogenous leukemia, chronic lymphocytic leukemia, and chronic myelogenous leukemia due to the use of tyrosine kinase inhibitors as the main drug in reducing mortality among these patients. Pericardial involvement is reported to be the most common cardiovascular complication of drug use among different kinds of leukemias. In this article, we try to collect cardiovascular evidence related to acute lymphocytic leukemia, acute myelogenous leukemia, chronic lymphocytic leukemia, and chronic myelogenous leukemia, separately.