Sublethal engagement of apoptotic pathways in residual cancer.

Cytotoxic chemo-, radio-, and targeted therapies frequently elicit apoptotic cancer cell death. Mitochondrial outer membrane permeabilization (MOMP) is a critical, regulated step in this apoptotic pathway. The residual cancer cells that survive treatment serve as the seeds of eventual relapse and are often functionally characterized by their transient tolerance of multiple therapeutic treatments. New studies suggest that, in these cells, a sublethal degree of MOMP, reflective of incomplete apoptotic commitment, is widely observed. Here, we review recent evidence that this sublethal MOMP drives the aggressive features of residual cancer cells while templating a host of unique vulnerabilities, highlighting how failed apoptosis may counterintuitively enable new therapeutic strategies to target residual disease (RD).

Lymphocyte-activation gene 3 protein expression in tumor-infiltrating lymphocytes is associated with a poor prognosis of ovarian clear cell carcinoma.

BACKGROUND: Histological analysis has revealed the need for new treatment techniques for epithelial ovarian cancer. Immune checkpoint inhibitors may be a new therapeutic strategy for ovarian clear cell carcinoma (OCCC). Lymphocyte-activation gene 3 (LAG-3), an immune checkpoint, is a poor prognostic factor and a new therapeutic target for several malignancies. In this study, we demonstrated the correlation between LAG-3 expression and the clinicopathological features of OCCC. We evaluated LAG-3 expression in tumor-infiltrating lymphocytes (TILs) via immunohistochemical analysis using tissue microarrays containing surgically resected specimens from 171 patients with OCCC. RESULTS: The number of LAG-3-positive cases was 48 (28.1%), whereas the number of LAG-3-negative cases was 123 (71.9%). LAG-3 expression significantly increased in patients with advanced stages (P = 0.036) and recurrence (P = 0.012); however, its expression did not correlate with age (P = 0.613), residual tumor (P = 0.156), or death (P = 0.086). Using the Kaplan - Meier method, LAG-3 expression was found to be correlated with poor overall survival (P = 0.020) and progression-free survival (P = 0.019). Multivariate analysis revealed LAG-3 expression (hazard ratio [HR] = 1.86; 95% confidence interval [CI], 1.00 - 3.44, P = 0.049) and residual tumor (HR = 9.71; 95% CI, 5.13 - 18.52, P < 0.001) as independent prognostic factors. CONCLUSION: Our study demonstrated that LAG-3 expression in patients with OCCC may be a useful biomarker for the prognosis of OCCC and could serve as a new therapeutic target.

The impact of Down syndrome-specific non-malignant hematopoietic regeneration in the bone marrow on the detection of leukemic measurable residual disease.

BACKGROUND: Detection of measurable residual disease detection (MRD) by flow cytometry after the first course of chemotherapy is a standard measure of early response in patients with acute myeloid leukemia (AML). Myeloid leukemia associated with Down Syndrome (ML-DS) is a distinct form of AML. Differences in steady-state and regenerating hematopoiesis between patients with or without DS are not well understood. This understanding is essential to accurately determine the presence of residual leukemia in patients with ML-DS. METHODS: A standardized antibody panel defined quantitative antigen expression in 115 follow-up bone marrow (BM) aspirates from 45 patients following chemotherapy for ML-DS or DS precursor B-cell acute lymphoblastic leukemia (B-ALL-DS) with the "difference from normal (ΔN)" technique. When possible, FISH and SNP/CGH microarray studies were performed on sorted cell fractions. RESULTS: 93% of BM specimens submitted post chemotherapy had a clearly identifiable CD34+ CD56+ population present between 0.06% and 2.6% of total non-erythroid cells. An overlapping CD34+ HLA-DRheterogeneous population was observed among 92% of patients at a lower frequency (0.04%-0.8% of total non-erythroid cells). In B-ALL-DS patients, the same CD34+ CD56+ HLA-DRheterogeneous expression was observed. FACS-FISH/Array studies demonstrated no residual genetic clones in the DS-specific myeloid progenitor cells. CONCLUSIONS: Non-malignant myeloid progenitors in the regenerating BM of patients who have undergone chemotherapy for either ML-DS or B-ALL-DS express an immunophenotype that is different from normal BM of non-DS patients. Awareness of this DS-specific non-malignant myeloid progenitor is essential to the interpretation of MRD by flow cytometry in patients with ML-DS.

Prognostic Impact and Phenotype of Residual Acute Myeloid Leukemia Stem Cells.

BACKGROUND: Leukemia stem cells (LSCs) have been demonstrated to be more therapy-resistant than leukemic blast cells reflecting measurable residual disease (MRD). CD34+CD38- cell frequency is an independent factor for relapse prediction and could therefore be used in the future to improve MRD assessment in acute myeloid leukemia (AML). This protocol is designed to enable accurate and reproducible immunophenotypic detection of measurable residual stem cell disease necessary for proper therapeutic decision and report their prognostic value in AML patients. METHODS: Fifty-four Novo AML adult patients diagnosed in the onco-hematology service of the "20 August 1953" Hospital in Casablanca. We analyzed phenotype and frequency of CD45dim CD34+CD38- cells in bone marrow samples from patients with AML and non-myeloid malignancies using six-color flow cytometry and a simple one-tube essay. RESULTS: For evaluation of leukemic stem cells, our gate strategy was based on the selection of CD34+CD38 - stem cells and leukemia associated immunophenotype approach. Positivity of CD123 or/and aberrant expression of primitive markers CD117 and HLA DR on stem cells discriminate leukemia stem cells from normal hematopoietic stem cells. We reported a statistically significant difference between expressions of primitive markers (CD117 and HLA DR) on leukemic stem cells. In addition, the frequency of LSCs after complete remission in post-induction was persistent in 50% of AML patients. CONCLUSIONS: Overall, we show that CD34+CD38-CD123+ as a basic phenotype, with aberrant phenotype detection of HLA DR and CD117 markers on stem cells, contributes to detecting LSCs which indicates the poor prognosis.

Leukemic stem cells as a target for eliminating acute myeloid leukemia: Gaps in translational research.

Relapse is common in acute myeloid leukemia (AML) and thought to be due to resistance of underlying leukemic stem cells (LSCs) to current standard therapies, although a lack of tools to measure the quantity and quality of these cells in patients precludes the clinical testing of this concept. This review discusses the current knowledge of LSC properties and appraises strategies aimed to bring the therapeutic targeting of LSCs to the bedside to improve patient outcomes. We highlight pathways and targets of interest and summarize available information on drugs that might eradicate LSCs. Future research is needed to close identified gaps in knowledge and provide evidence for the clinical efficacy of LSC-directed therapies to support the development of treatments that eliminate residual disease and prevent relapse, thereby increasing the cure rates of patients with AML.

Relevance of polyclonal plasma cells and post-therapy immunomodulation in measurable residual disease assessment in multiple myeloma.

BACKGROUND: Immunophenotypic profile and post-therapy alteration in antigenic expression were evaluated in normal, reactive, and aberrant plasma cells (NPC, RPC, and APC) for impact on measurable residual disease (MRD) assessment in multiple myeloma (MM). METHODS: Samples from non-MM staging marrow (n = 30), Hodgkin's lymphoma (n = 30) and MM (n = 724) were prospectively evaluated for expression profiles of NPC, RPC, and APC using antigens recommended in consensus guidelines. RESULTS: Polyclonal NPC-RPC demonstrated aberrations for all antigens evaluated with a higher frequency of aberrancies in post-therapy samples compared to treatment naïve samples (p < 0.001%). Immunomodulation in APC was observed in 79% of post-therapy samples with a change in expression of 1, 2, and ≥3 antigens in 19.9%, 15.6%, and 43.5% samples, respectively. In 13.4% of samples, APC showed no aberrancy and aberrant status was assigned based on cytoplasmic light chain restriction (cyLCR) alone. 9% samples with an admixture of NPC and APC displayed normal cytoplasmic kappa to lambda ratio (cyKLR) when the percentage of APC of total PC (neoplastic plasma cell index, NPCI), was below 25% and 50% for kappa and lambda restricted cases, respectively. CONCLUSION: The panorama and high frequency of antigenic aberrations on polyclonal PC signify the importance of MRD assay validation on a large cohort under normal and reactive conditions. Frequent Immunophenotypic shifts in APC re-confirm the redundancy of baseline immunophenotype for MRD evaluation. Small clones of APC may be missed by assessment of cyKLR alone and therefore, surface marker aberrancy supported by cyLCR is required for definitive assignment of residual APC.

Targeting ULK1 in cancer stem cells: insight from chronic myeloid leukemia.

Minimal residual disease (MRD) refers to a low number of cells that persist anti-cancer treatment and is the major cause of relapse in solid cancers and leukemias. In chronic myeloid leukemia (CML), a paradigm for stem cell-driven cancer, MRD is maintained by tyrosine kinase inhibitor (TKI)-insensitive leukemic stem cells (LSCs), which may rely on fundamental metabolic processes to resist drug treatment. Macroautophagy/autophagy is a cytoprotective process that has been highlighted as critical for sustaining LSC survival during TKI treatment in robust experimental models of CML. Our recent study shows that the autophagy-initiating kinase ULK1 is required for maintaining energy and redox balance in CML LSCs. Pharmacological inhibition of ULK1 results in stress-induced differentiation of LSCs, rendering them sensitive to TKI treatment, uncovering a promising strategy for selective eradication of LSCs in CML patients.Abbreviations CML: chronic myeloid leukemia; LSC: leukemic stem cell; MAPK: mitogen-activated protein kinase; MRD: minimal residual disease; TKI: tyrosine kinase inhibitor.

NT5E gene and CD38 protein as potential prognostic biomarkers for childhood B-acute lymphoblastic leukemia.

The risk stratification of B-acute lymphoblastic leukemia (B-ALL) is based on clinical and biological factors. However, B-ALL has significant biological and clinical heterogeneity and 50% of B-ALL patients do not have defined prognostic markers. In this sense, the identification of new prognostic biomarkers is necessary. Considering different cohorts of childhood B-ALL patients, gene (DPP4/CD38/ENTPD1/NT5E) and protein (CD38/CD39/CD73) expressions of ectonucleotidases were analyzed in silico and ex vivo and the association with prognosis was established. In univariate analyses, expression of NT5E was significantly associated with worse progression-free survival (PFS) in bone marrow (BM) samples. In multivariate analyses, Kaplan-Meier analysis, and log-rank test, higher NT5E expression predicted unfavorable PFS in BM samples. Considering minimal residual disease (MRD), higher levels of cellularity were associated with the high NT5E expression at day 8 of induction therapy. In addition, we observed that white blood cells (WBC) of childhood B-ALL patients had more CD38 compared to the same cell population of healthy donors (HD). In fact, MRD > 0.1% patients had higher CD38 protein expression on WBC in comparison to HD. Noteworthy, we observed higher CD38 expression on WBC than blasts in MRD > 0.1% patients. We suggest that NT5E gene and CD38 protein expression, of the ectonucleotidases family, could provide interesting prognostic biomarkers for childhood B-ALL.

Autophagy and Hepatic Tumor Microenvironment Associated Dormancy.

The goal of successful cancer treatment is targeting the eradication of cancer cells. Although surgical removal of the primary tumors and several rounds of chemo- and radiotherapy reduce the disease burden, in some cases, asymptomatic dormant cancer cells may still exist in the body. Dormant cells arise from the disseminated tumor cells (DTCs) from the primary lesion. DTCs escape from immune system and cancer therapy and reside at the secondary organ without showing no sign of proliferation. However, under some conditions. dormant cells can be re-activated and enter a proliferative state even after decades. As a stress response mechanism, autophagy may help the adaptation of DTCs at this futile foreign microenvironment and may control the survival and re-activation of dormant cells. Studies indicate that hepatic microenvironment serves a favorable condition for cancer cell dormancy. Although, no direct study was pointing out the role of autophagy in liver-assisted dormancy, involvement of autophagy in both liver microenvironment, health, and disease conditions has been indicated. Therefore, in this review article, we will summarize cancer dormancy and discuss the role and importance of autophagy and hepatic microenvironment in this context.

Acute myeloid leukemia maturation lineage influences residual disease and relapse following differentiation therapy.

Acute myeloid leukemia (AML) is a malignancy of immature progenitor cells. AML differentiation therapies trigger leukemia maturation and can induce remission, but relapse is prevalent and its cellular origin is unclear. Here we describe high resolution analysis of differentiation therapy response and relapse in a mouse AML model. Triggering leukemia differentiation in this model invariably produces two phenotypically distinct mature myeloid lineages in vivo. Leukemia-derived neutrophils dominate the initial wave of leukemia differentiation but clear rapidly and do not contribute to residual disease. In contrast, a therapy-induced population of mature AML-derived eosinophil-like cells persists during remission, often in extramedullary organs. Using genetic approaches we show that restricting therapy-induced leukemia maturation to the short-lived neutrophil lineage markedly reduces relapse rates and can yield cure. These results indicate that relapse can originate from therapy-resistant mature AML cells, and suggest differentiation therapy combined with targeted eradication of mature leukemia-derived lineages may improve disease outcome.

Engineering Tools for Regulating Hypoxia in Tumour Models.

Major advances in the field of genomic technologies have led to an improvement in cancer diagnosis, classification and prognostication. However, many cancers remain incurable due to the development of drug resistance, minimal residual disease (MRD) and disease relapse, highlighting an incomplete understanding of the mechanisms underlying these processes. In recent years, the impact of non-genetic factors on neoplastic transformations has increasingly been acknowledged, and growing evidence suggests that low oxygen (O2 ) levels (ie hypoxia) in the tumour microenvironment play a critical role in the development and treatment of cancer. As a result, there is a growing need to develop research tools capable of reproducing physiologically relevant O2 conditions encountered by cancer cells in their natural environments in order to gain in-depth insight into tumour cell metabolism and function. In this review, the authors highlight the importance of hypoxia in the pathogenesis of malignant diseases and provide an overview of novel engineering tools that have the potential to further drive this evolving, yet technically challenging, field of cancer research.

Salvage Radiation Treatment for Primary Refractory Diffuse Large B-cell Lymphoma After Chimeric Antigen Receptor (CAR) T-cell Therapy: A Case Report.

BACKGROUND: Treatment of refractory/relapsing diffuse large B cell (R/R DLBCL) lymphoma remains a challenge. Radiation therapy (RT) has versatile roles in R/R DLBCL treatment: it can be used in the peri-transplant setting for transplant-eligible candidates, or as a salvage or palliation therapy depending on the extent of the disease in transplant-ineligible patients. The introduction of chimeric antigen receptor (CAR) T-cell therapy has changed the landscape of R/R DLBCL. RT has been used as a bridging therapy to CAR T-cell therapy in order to control disease progression during its manufacturing period. However, optimal RT and CAR T-cell therapy integration is still unknown. Salvage strategies for R/R DLBCL post-CAR T-cell therapy have been little studied. CASE REPORT: Here, we present a case of primary refractory DLBCL with residual disease post-CAR T-cell therapy successfully treated with salvage RT. CONCLUSION: Radiotherapy could be an effective salvage strategy for R/R DLBCL post-CAR T-cell therapy. Exact mechanisms await exploring.

Inhibition of nuclear export restores nuclear localization and residual tumor suppressor function of truncated SMARCB1/INI1 protein in a molecular subset of atypical teratoid/rhabdoid tumors.

Loss of nuclear SMARCB1 (INI1/hSNF5/BAF47) protein expression due to biallelic mutations of the SMARCB1 tumor suppressor gene is a hallmark of atypical teratoid/rhabdoid tumors (ATRT), but the presence of cytoplasmic SMARCB1 protein in these tumors has not yet been described. In a series of 102 primary ATRT, distinct cytoplasmic SMARCB1 staining on immunohistochemistry was encountered in 19 cases (19%) and was highly over-represented in cases showing pathogenic sequence variants leading to truncation or mutation of the C-terminal part of SMARCB1 (15/19 vs. 4/83; Chi-square: 56.04, p = 1.0E-10) and, related to this, in tumors of the molecular subgroup ATRT-TYR (16/36 vs. 3/66; Chi-square: 24.47, p = 7.6E-7). Previous reports have indicated that while SMARCB1 lacks a bona fide nuclear localization signal, it harbors a masked nuclear export signal (NES) and that truncation of the C-terminal region results in unmasking of this NES leading to cytoplasmic localization. To determine if cytoplasmic localization found in ATRT is due to unmasking of NES, we generated GFP fusions of one of the SMARCB1 truncating mutations (p.Q318X) found in the tumors along with a p.L266A mutation, which was shown to disrupt the interaction of SMARCB1-NES with exportin-1. We found that while the GFP-SMARCB1(Q318X) mutant localized to the cytoplasm, the double mutant GFP-SMARCB1(Q318X;L266A) localized to the nucleus, confirming NES requirement for cytoplasmic localization. Furthermore, cytoplasmic SMARCB1(Q318X) was unable to cause senescence as determined by morphological observations and by senescence-associated ß-galactosidase assay, while nuclear SMARCB1(Q318X;L266A) mutant regained this function. Selinexor, a selective exportin-1 inhibitor, was effective in inhibiting the nuclear export of SMARCB1(Q318X) and caused rapid cell death in rhabdoid tumor cells. In conclusion, inhibition of nuclear export restores nuclear localization and residual tumor suppressor function of truncated SMARCB1. Therapies aimed at preventing nuclear export of mutant SMARCB1 protein may represent a promising targeted therapy in ATRT harboring truncating C-terminal SMARCB1 mutations.

Adipocyte-like signature in ovarian cancer minimal residual disease identifies metabolic vulnerabilities of tumor-initiating cells.

Similar to tumor-initiating cells (TICs), minimal residual disease (MRD) is capable of reinitiating tumors and causing recurrence. However, the molecular characteristics of solid tumor MRD cells and drivers of their survival have remained elusive. Here we performed dense multiregion transcriptomics analysis of paired biopsies from 17 ovarian cancer patients before and after chemotherapy. We reveal that while MRD cells share important molecular signatures with TICs, they are also characterized by an adipocyte-like gene expression signature and a portion of them had undergone epithelial-mesenchymal transition (EMT). In a cell culture MRD model, MRD-mimic cells showed the same phenotype and were dependent on fatty acid oxidation (FAO) for survival and resistance to cytotoxic agents. These findings identify EMT and FAO as attractive targets to eradicate MRD in ovarian cancer and make a compelling case for the further testing of FAO inhibitors in treating MRD.

Post-induction MRD by FCM and GATA1-PCR are significant prognostic factors for myeloid leukemia of Down syndrome.

Myeloid leukemia of Down syndrome (ML-DS) is associated with good response to chemotherapy, resulting in favorable outcomes. However, no universal prognostic factors have been identified to date. To clarify a subgroup with high risk of relapse, the role of minimal residual disease (MRD) was explored in the AML-D11 trial by the Japanese Pediatric Leukemia/Lymphoma Study Group. MRD was prospectively evaluated at after induction therapy and at the end of all chemotherapy, using flow cytometry (FCM-MRD) and GATA1-targeted deep sequencing (GATA1-MRD). A total of 78 patients were eligible and 76 patients were stratified to the standard risk (SR) group by morphology. In SR patients, FCM-MRD and GATA1-MRD after induction were positive in 5/65 and 7/59 patients, respectively. Three-year event-free survival (EFS) and overall survival (OS) rates were 95.0% and 96.7% in the FCM-MRD-negative population, and 60.0% and 80.0% in the positive population. Three-year EFS and OS rates were both 98.1% in the GATA1-MRD-negative population, and 57.1% and 71.4% in the positive population. Adjusted hazard ratios for associations of FCM-MRD with EFS were 14.67 (p = 0.01). Detection of MRD by either FCM or GATA1 after initial induction therapy represents a significant prognostic factor for predicting ML-DS relapse.

Biomarkers for site-specific response to neoadjuvant chemotherapy in epithelial ovarian cancer: relating MRI changes to tumour cell load and necrosis.

BACKGROUND: Diffusion-weighted magnetic resonance imaging (DW-MRI) potentially interrogates site-specific response to neoadjuvant chemotherapy (NAC) in epithelial ovarian cancer (EOC). METHODS: Participants with newly diagnosed EOC due for platinum-based chemotherapy and interval debulking surgery were recruited prospectively in a multicentre study (n = 47 participants). Apparent diffusion coefficient (ADC) and solid tumour volume (up to 10 lesions per participant) were obtained from DW-MRI before and after NAC (including double-baseline for repeatability assessment in n = 19). Anatomically matched lesions were analysed after surgical excision (65 lesions obtained from 25 participants). A trained algorithm determined tumour cell fraction, percentage tumour and percentage necrosis on histology. Whole-lesion post-NAC ADC and pre/post-NAC ADC changes were compared with histological metrics (residual tumour/necrosis) for each tumour site (ovarian, omental, peritoneal, lymph node). RESULTS: Tumour volume reduced at all sites after NAC. ADC increased between pre- and post-NAC measurements. Post-NAC ADC correlated negatively with tumour cell fraction. Pre/post-NAC changes in ADC correlated positively with percentage necrosis. Significant correlations were driven by peritoneal lesions. CONCLUSIONS: Following NAC in EOC, the ADC (measured using DW-MRI) increases differentially at disease sites despite similar tumour shrinkage, making its utility site-specific. After NAC, ADC correlates negatively with tumour cell fraction; change in ADC correlates positively with percentage necrosis. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov NCT01505829.

Vascular endothelial growth factor (VEGF), tissue inhibitors of metalloproteinase-1 (TIMP-1) and nail fold capillaroscopy changes in children and adolescents with Gaucher disease; relation to residual disease severity.

BACKGROUND: Gaucher disease (GD) is caused by functional defects of the acid ß-glucocerebrosidase enzyme, with accumulation of glucosylceramide in the macrophage lineage lysosomes causing multisystem abnormalities. However, some GD manifestations can't be explained by Gaucher-cells infiltration. Recent studies emphasized the role of inflammation in GD. AIM: To compare the level of TIMP1 (Tissue-inhibitory metalloproteinase-1) and VEGF (Vascular-endothelial growth factor) and nail-fold capillaroscopy (NFC) changes in children and adolescents (CA) with GD and controls and correlate them to disease-severity, genotype, visceral and neurological manifestations. METHODOLOGY: Fifty-three CA with GD were compared to 52 age and sex matched healthy controls stressing on ERT (enzyme replacement therapy) dose and duration, pulmonary, hematological and neurological manifestations with assessment of severity-scoring index (SSI). Full neurological, abdominal and chest examinations were done. Sonographic liver and spleen volumes and NFC were assessed. GD genotype was done. Serum TIMP-1 and VEGF were measured. RESULTS: CA with GD had significantly higher TIMP-1 (P < 0.001) and VEGF (P < 0.001) than controls. Type 3CA with GD had significantly higher TIMP-1 (P = 0.004) and VEGF (P = 0.035) than type 1. There was a significant positive correlation between TIMP-1 and each of VEGF (P < 0.001), SSI (P < 0.001) and NFC (P < 0.001). A significant positive relation was found between TIMP-1 and convulsions (P = 0.002), dysphagia (P = 0.008), opthalmoplegia (P = 0.038) and developmental delay (P < 0.001). Multi-variate logistic regression analysis for predictors of children and adolescents with GD revealed that its most correlated to TIMP-1 (P = 0.008) and NFC changes (P = 0.025). CONCLUSION: Macrophage proliferation in GD modulates local inflammation, micro-angiopathy and neo-angiogenesis. NFC can be used as a noninvasive indicator of microangiopathy in GD.