Search

Despite effective new therapies, adaptive resistance remains the main obstacle in acute myelogenous leukemia (AML) therapy. Autophagy induction is a key mechanism for adaptive resistance. Leukemic blasts at diagnosis express higher levels of the apical autophagy kinase ULK1 compared with normal hematopoietic cells. Exposure to chemotherapy and targeted agents upregulate ULK1, hence we hypothesize that developing ULK1 inhibitors may present the unique opportunity for clinical translation of autophagy inhibition. Accordingly, we demonstrate that ULK1 inhibition, by genetic and pharmacologic means, suppresses treatment-induced autophagy, overcomes adaptive drug-resistance, and synergizes with chemotherapy and emerging antileukemia agents like venetoclax (ABT-199). The study next aims at exploring the underlying mechanisms. Mechanistically, ULK1 inhibition downregulates MCL1 antiapoptotic gene, impairs mitochondrial function and downregulates components of the CD44-xCT system, resulting in impaired reactive oxygen species (ROS) mitigation, DNA damage, and apoptosis. For further validation, several mouse models of AML were generated. In these mouse models, ULK1 deficiency impaired leukemic cell homing and engraftment, delayed disease progression, and improved survival. Therefore, in the study, we validated our hypothesis and identified ULK1 as an important mediator of adaptive resistance to therapy and an ideal candidate for combination therapy in AML. Therefore, we propose ULK1 inhibition as a therapeutically relevant treatment option to overcome adaptive drug-resistance in AML., Implications: ULK1 drives a cell-intrinsic adaptive resistance in AML and targeting ULK1-mediated autophagy can synergize with existing and emerging AML therapies to overcome drug-resistance and induce apoptosis., (©2023 American Association for Cancer Research.)

Despite the clinical success of T-cell checkpoint blockade, most patients with cancer still fail to have durable responses to immunotherapy. The molecular mechanisms driving checkpoint blockade resistance, whether preexisting or evolved, remain unclear. To address this critical knowledge gap, we treated B16 melanoma with the combination of CTLA-4, PD-1, and PD-L1 blockade and a Flt3 ligand vaccine (≥75% curative), isolated tumors resistant to therapy, and serially passaged them in vivo with the same treatment regimen until they developed complete resistance. Using gene expression analysis and immunogenomics, we determined the adaptations associated with this resistance phenotype. Checkpoint resistance coincided with acquisition of a "hypermetabolic" phenotype characterized by coordinated upregulation of the glycolytic, oxidoreductase, and mitochondrial oxidative phosphorylation pathways. These resistant tumors flourished under hypoxic conditions, whereas metabolically starved T cells lost glycolytic potential, effector function, and the ability to expand in response to immunotherapy. Furthermore, we found that checkpoint-resistant versus -sensitive tumors could be separated by noninvasive MRI imaging based solely on their metabolic state. In a cohort of patients with melanoma resistant to both CTLA-4 and PD-1 blockade, we observed upregulation of pathways indicative of a similar hypermetabolic state. Together, these data indicated that melanoma can evade T-cell checkpoint blockade immunotherapy by adapting a hypermetabolic phenotype., (©2020 American Association for Cancer Research.)

Early clinical trials using murine double minute 2 (MDM2) inhibitors demonstrated proof-of-concept of p53-induced apoptosis by MDM2 inhibition in cancer cells; however, not all wild-type TP53 tumors are sensitive to MDM2 inhibition. Therefore, more potent inhibitors and biomarkers predictive of tumor sensitivity are needed. The novel MDM2 inhibitor DS-3032b is 10-fold more potent than the first-generation inhibitor nutlin-3a. TP53 mutations were predictive of resistance to DS-3032b, and allele frequencies of TP53 mutations were negatively correlated with sensitivity to DS-3032b. However, sensitivity to DS-3032b of TP53 wild-type tumors varied greatly. We thus used two methods to create predictive gene signatures. First, by comparing sensitivity to MDM2 inhibition with basal mRNA expression profiles in 240 cancer cell lines, a 175-gene signature was defined and validated in patient-derived tumor xenograft models and ex vivo human acute myeloid leukemia (AML) cells. Second, an AML-specific 1,532-gene signature was defined by performing random forest analysis with cross-validation using gene expression profiles of 41 primary AML samples. The combination of TP53 mutation status with the two gene signatures provided the best positive predictive values (81% and 82%, compared with 62% for TP53 mutation status alone). In addition, the top-ranked 50 genes selected from the AML-specific 1,532-gene signature conserved high predictive performance, suggesting that a more feasible size of gene signature can be generated through this method for clinical implementation. Our model is being tested in ongoing clinical trials of MDM2 inhibitors. Significance: This study demonstrates that gene expression profiling combined with TP53 mutational status predicts antitumor effects of MDM2 inhibitors in vitro and in vivo Cancer Res; 78(10); 2721-31. ©2018 AACR ., (©2018 American Association for Cancer Research.)

Peripheral blood chronic lymphocytic leukemia (CLL) cells are quiescent but have active transcription and translation processes, suggesting that these lymphocytes are metabolically active. Based on this premise, the metabolic phenotype of CLL lymphocytes was investigated by evaluating the two intracellular ATP-generating pathways. Metabolic flux was assessed by measuring glycolysis as extracellular acidification rate (ECAR) and mitochondrial oxidative phosphorylation as oxygen consumption rate (OCR) and then correlated with prognostic factors. Further, the impact of B-cell receptor signaling (BCR) on metabolism was determined by genetic ablation and pharmacological inhibitors. Compared with proliferative B-cell lines, metabolic fluxes of oxygen and lactate were low in CLL cells. ECAR was consistently low, but OCR varied considerably in human patient samples ( n = 45). Higher OCR was associated with poor prognostic factors such as ZAP 70 positivity, unmutated IGHV, high β2M levels, and higher Rai stage. Consistent with the association of ZAP 70 and IGHV unmutated status with active BCR signaling, genetic ablation of BCR mitigated OCR in malignant B cells. Similarly, knocking out PI3Kδ, a critical component of the BCR pathway, decreased OCR and ECAR. In concert, PI3K pathway inhibitors dramatically reduced OCR and ECAR. In harmony with a decline in metabolic activity, the ribonucleotide pools in CLL cells were reduced with duvelisib treatment. Collectively, these data demonstrate that CLL metabolism, especially OCR, is linked to prognostic factors and is curbed by BCR and PI3K pathway inhibition. Implications: This study identifies a relationship between oxidative phosphorylation in CLL and prognostic factors providing a rationale to therapeutically target these processes. Mol Cancer Res; 15(12); 1692-703. ©2017 AACR ., (©2017 American Association for Cancer Research.)

Unlabelled: Immune checkpoint blockade represents a major breakthrough in cancer therapy; however, responses are not universal. Genomic and immune features in pretreatment tumor biopsies have been reported to correlate with response in patients with melanoma and other cancers, but robust biomarkers have not been identified. We studied a cohort of patients with metastatic melanoma initially treated with cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) blockade (n = 53) followed by programmed death-1 (PD-1) blockade at progression (n = 46), and analyzed immune signatures in longitudinal tissue samples collected at multiple time points during therapy. In this study, we demonstrate that adaptive immune signatures in tumor biopsy samples obtained early during the course of treatment are highly predictive of response to immune checkpoint blockade and also demonstrate differential effects on the tumor microenvironment induced by CTLA4 and PD-1 blockade. Importantly, potential mechanisms of therapeutic resistance to immune checkpoint blockade were also identified., Significance: These studies demonstrate that adaptive immune signatures in early on-treatment tumor biopsies are predictive of response to checkpoint blockade and yield insight into mechanisms of therapeutic resistance. These concepts have far-reaching implications in this age of precision medicine and should be explored in immune checkpoint blockade treatment across cancer types. Cancer Discov; 6(8); 827-37. ©2016 AACR.See related commentary by Teng et al., p. 818This article is highlighted in the In This Issue feature, p. 803., Competing Interests: No other potential conflicts of interest were disclosed., (©2016 American Association for Cancer Research.)