Pursuing dynamics of minimal residual leukemic subclones in relapsed and refractory acute myeloid leukemia during conventional therapy

BACKGROUND

Acute myeloid leukemia (AML) is characterized by clonal heterogeneity, leading to frequent relapses and drug resistance despite intensive clinical therapy. Although AML's clonal architecture has been addressed in many studies, practical monitoring of dynamic changes in those subclones during relapse and treatment is still understudied.

METHOD

Fifteen longitudinal bone marrow (BM) samples were collected from three relapsed and refractory (R/R) AML patients. Using droplet digital polymerase chain reaction (ddPCR), the frequencies of patient's leukemic variants were assessed in seven cell populations that were isolated from each BM sample based on cellular phenotypes. By quantifying mutant clones at the diagnosis, remission, and relapse stages, the distribution of AML subclones was sequentially monitored.

RESULTS

Minimal residual (MR) leukemic subclones exhibit heterogeneous distribution among BM cell populations, including mature leukocyte populations. During AML progression, these subclones undergo active phenotypic transitions and repopulate into distinct cell population regardless of normal hematopoiesis hierarchic order. Of these, MR subclones in progenitor populations of patient BM predominantly carry MR leukemic properties, leading to more robust expansion and stubborn persistence than those in mature populations. Moreover, a minor subset of MR leukemic subclones could be sustained at an extremely low frequency without clonal expansion during relapse.

CONCLUSIONS

In this study, we observed treatment persistent MR leukemic subclones and their phenotypic changes during the treatment process of R/R AML patients. This underscores the importance of preemptive inhibition of clonal promiscuity in R/R AML, proposing a practical method for monitoring AML MR subclones.

Abstract 3873: Candidate drug screening for TP53-mutated AML

Acute myeloid leukemia (AML) is a clonal blood malignancy characterized by arrested maturation and abnormal proliferation of hematopoietic precursor cells. This paralysis of normal bone marrow function leads to severe decreased immune function and bleeding tendency, and if not treated, it is an acute disease that dies within a few months due to rapid progression of AML. TP53 mutations occur in 5% to 10% of patients with de-novo acute myeloid leukemia (AML), with higher frequency in patients with relapsed/refractory AML. The treatment approach for many years has used combination chemotherapy, with usually an anthracycline and cytarabine as the foundation. These induction therapy's complete response is achieved in 60 to 85% of adults who are 60 years of age or younger. In patients who are older than 60 years of age, complete response rates are inferior 40 to 60%. TP53 mutated acute myeloid leukemia (AML) responds poorly to the conventional induction therapy and has a short overall survival rate with a median of 5-9 months. Poor outcomes in TP53 mutated AML following chemotherapy have been observed and treatment options remain limited. Therefore, this study attempted to explore the drug candidates for effective treatment of TP53 mutated AML. To study the cellular response to TP53-targeted therapy, we used the human AML cell line Kasumi-1, which harbors a homozygous TP53 mutation. We treated Kasumi-1 cells with cytarabine and Idarubicin combi-treatment. And we produced Drug Tolerant Persisters (DTPs) which is a minor population of cancer cells may evade cell death from chemotherapy and targeted therapy by entering a reversible slow proliferation state. Similar to a previously described DTP phenotype the DTPs that survive cytarabine and Idarubicin combi-treatment displayed cell-cycle arrest and resistance to further cytarabine and Idarubicin combi-treatment. And we selected 125 drug candidates that would be effective for TP53 mutated AML through in silico analysis and therapy strategies targeting p53. The drug candidates are composed of Compounds with the ability to reactivate mutant p53, Compounds directly target mutant p53, Synthetic lethal partners with mutant p53, and Compounds with the ability to anti-Leukemic Stem Cell and antineoplastic. We single out 46 of the 125 compounds for functional validation in DTPs. We chose these compounds because many of them are similar subtypes, suggesting they may have a common effect and mechanism. Using in vitro Cytotoxicity assay, we screened 46 candidate compounds at multiple doses and confirmed several drugs that effectively eliminate DTPs. Collectively, our study indicates that the combination of conventional drug and validated drug has the potential to eliminate DTPs and therefore prevent minimal residual disease, mutational drug resistance, and relapse in TP53-mutant AML.

Citation Format: Daehyeon Gwak, Dong Chan Kim, Heejun Jang, Jun Liu, Ja Min Byun, Junshik Hong, Dong Yeop Shin, Sung-Soo Yoon. Candidate drug screening for TP53-mutated AML. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3873.

Abstract 1034: Pharmacological GLUT3 salvage augments the efficacy of vitamin C induced TET2 restoration in AML cells

Background and purpose: Vitamin C has been demonstrated to regulate hematopoietic stem cells (HSC) frequencies and leukemogenesis by augmenting and restoring TET2 function, potentially acting as a novel treatment strategy for leukemia. In a previous study (Liu et al, 2020 Br J Cancer), we showed that GLUT3, a major vitamin C transporter in acute myeloid leukemia (AML) cells, was significantly decreased in AML blasts compared with normal hematopoietic cells, which impedes TET2 restoration and promotes leukemia progression. Although GLUT3 could be a potential biomarker to predict the vitamin C treatment efficiency, a remaining question was whether GLUT3 can be a druggable target in AML. In this study, we aim to investigate the therapeutic value of GLUT3 salvage in AML

Methods: GLUT3 salvage was conducted on GLUT3 deficient AML cell line OCI-AML3 using GLUT3 overexpression lentivirus transduction or AICAR (an AMPK activator, Phase 3) treatment. The 5hmC DNA dot blotting assay was carried out to explore the TET2 function. The leukemic phenotypes were evaluated using soft agar colony formation assay, migration assay, and invasion assay.

Results: To verify if turning on GLUT3 enhances the efficacy of vitamin C treatment, the GLUT3 overexpression lentivirus or empty vector lentivirus was transduced into the OCI-AML3 cell line. The transcription level of SLC2A3 (gene encoded GLUT3) was increased to 8 times in the GLUT3 overexpression cell line. Then, 5hmC DNA dot blotting results showed that GLUT3 overexpression further significantly raised the 5hmC level after 250 µM vitamin C treatment. Consistent with augmentation of TET2 function, turning on GLUT3 with vitamin C treatment alleviated leukemic phenotypes compared with empty vector group. Pharmacological GLUT3 salvage using AICAR 0.5 mM 48 hours could achieve the same effect as lentivirus transduction, in terms of GLUT3 expression level, augmentation of TET2 function, and enhancement of vitamin C anti-leukemic effect. Notably, AICAR treatment only induced GLUT3 expression while showed no effect on GLUT5.

Conclusion: GLUT3 salvage could augment the efficacy of vitamin C induced TET2 restoration in AML cells. Pharmacological GLUT3 salvage using AICAR sheds new light on overcoming GLUT3 deficiency in AML.

Citation Format: Jun Liu, Suji Min, Seojeong Kim, Daehyeon Gwak, Junshik Hong, Sungsoo Yoon. Pharmacological GLUT3 salvage augments the efficacy of vitamin C induced TET2 restoration in AML cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1034.