The evolution of hematopoietic cells under cancer therapy.

Chemotherapies may increase mutagenesis of healthy cells and change the selective pressures in tissues, thus influencing their evolution. However, their contributions to the mutation burden and clonal expansions of healthy somatic tissues are not clear. Here, exploiting the mutational footprint of some chemotherapies, we explore their influence on the evolution of hematopoietic cells. Cells of Acute Myeloid Leukemia (AML) secondary to treatment with platinum-based drugs show the mutational footprint of these drugs, indicating that non-malignant blood cells receive chemotherapy mutations. No trace of the 5-fluorouracil (5FU) mutational signature is found in AMLs secondary to exposure to 5FU, suggesting that cells establishing the leukemia could be quiescent during treatment. Using the platinum-based mutational signature as a barcode, we determine that the clonal expansion originating the secondary AMLs begins after the start of the cytotoxic treatment. Its absence in clonal hematopoiesis cases is consistent with the start of the clonal expansion predating the exposure to platinum-based drugs.

Cytotoxic Therapy-Induced Effects on Both Hematopoietic and Marrow Stromal Cells Promotes Therapy-Related Myeloid Neoplasms.

Therapy-related myeloid neoplasms (t-MNs) following treatment with alkylating agents are characterized by a del(5q), complex karyotypes, alterations of TP53, and a dismal prognosis. To decipher the molecular pathway(s) leading to the pathogenesis of del(5q) t-MN and the effect(s) of cytotoxic therapy on the marrow microenvironment, we developed a mouse model with loss of two key del(5q) genes, EGR1 and APC, in hematopoietic cells. We used the well-characterized drug, N-ethyl-N-nitrosurea (ENU) to demonstrate that alkylating agent exposure of stromal cells in the microenvironment increases the incidence of myeloid disease. In addition, loss of Trp53 with Egr1 and Apc was required to drive the development of a transplantable leukemia, and accompanied by the acquisition of somatic mutations in DNA damage response genes. ENU treatment of mesenchymal stromal cells induced cellular senescence, and led to the acquisition of a senescence-associated secretory phenotype, which may be a critical microenvironmental alteration in the pathogenesis of myeloid neoplasms.

Acute myeloid leukemia and myelodysplastic syndrome after adjuvant chemotherapy: A population-based study among older breast cancer patients.

BACKGROUND: Chemotherapy for early breast cancer is associated with a small risk of developing myelodysplastic syndrome (MDS) and/or acute myeloid leukemia (AML). The aim of this study was to determine the risk of developing AML or MDS after modern adjuvant chemotherapy in older breast cancer patients and to further define the risk of individual chemotherapy regimens. METHODS: Patients diagnosed with stage I to III breast cancer from 2003 to 2009 were identified in the Surveillance, Epidemiology, and End Results-Medicare and Texas Cancer Registry-Medicare linked databases. The development of AML/MDS, chemotherapy use, and comorbidities were identified with International Classification of Diseases, Ninth Revision and Healthcare Common Procedure Coding System codes. Analyses included descriptive statistics, cumulative incidences, and Cox proportional hazards models to estimate the hazard of AML/MDS after adjustments for clinically relevant covariates. RESULTS: In all, 92,110 patients were included; after a median follow-up of 85 months, the overall rates per 1000 person-years were 0.65 for AML and 1.56 for MDS. Patients who received an anthracycline (A) or anthracycline and taxane (A+T) regimen were more likely to develop AML (hazard ratio [HR] for A, 1.70; 95% confidence interval [CI], 1.16-2.50; HR for A+T, 1.68; 95% CI, 1.22-2.30) or MDS (HR for A, 2.18; 95% CI, 1.70-2.80; HR for A+T, 1.62; 95% CI, 1.29-2.03) than patients who did not receive chemotherapy. Patients using docetaxel and cyclophosphamide (TC) were not at increased risk for AML or MDS. CONCLUSIONS: Adjuvant chemotherapy is associated with a small but significant increase in the risk of AML and MDS, especially with regimens that include A. Longer follow-up is needed to confirm that risk is not increased with the recently adopted TC regimen. Cancer 2018;124:899-906. © 2017 American Cancer Society.

THERAPY-RELATED T/MYELOID MIXED PHENOTYPE ACUTE LEUKEMIA IN A PATIENT TREATED WITH CHEMOTHERAPY FOR CUTANEOUS DIFFUSE LARGE B CELL LYMPHOMA.

Mixed-phenotype acute leukemia is a rare form of leukemia that is associated with a poor prognosis. Most cases of mixed-phenotype acute leukemia are de novo. However, therapy-related mixed-phenotype acute leukemia can occur, and are often associated with exposure to topoisomerase-II inhibitors and alkylating agents. There are no known treatment guidelines for therapy-related mixed-phenotype acute leukemia. We present a patient with T/myeloid mixed-phenotype acute leukemia secondary to rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone R-CHOP chemotherapy for primary cutaneous diffuse large B-cell lymphoma. The patient's leukemic cells express CD34, an immaturity marker, CD3, a T-cell marker, and myeloperoxidase, a myeloid marker, and her history of chemotherapy for previous lymphoma supports the diagnosis of therapy-related T/myeloid mixed phenotype acute leukemia. Clinicians should be aware that this entity could be associated with R-CHOP chemotherapy. Given the complexity in diagnosis, and lack of treatment guidelines, a further understanding of the pathological and genetic principles of therapy-related mixed-phenotype acute leukemia will assist in future efforts to treat and categorize these patients. Mixed phenotype acute leukemia is a rare entity that accounts for two to five percent of all acute leukemias. Therapy- related mixed phenotype acute leukemia is an exceedingly rare hematological neoplasm that accounts for less than one percent of acute leukemias. We describe a case of therapy-related T/myeloid mixed phenotype acute leukemia following rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone R-CHOP chemotherapy for primary cutaneous diffuse large B-cell lymphoma DLBCL. The patient is a 63-year-old female who presented with several cutaneous nodules diagnosed as primary cutaneous DLBCL. The patient received R-CHOP chemotherapy and achieved remission. She remained in remission for four years until she presented with dyspnea, night sweats, weakness, and diffuse lymphadenopathy. Her presentation was initially concerning for recurrent lymphoma; however, a bone marrow biopsy and aspirate and a lymph node biopsy revealed a distinct blast population consistent with T/myeloid mixed phenotype acute leukemia T/M-MPAL. Given the patient's history of previous chemotherapy exposure, our patient represents a case of therapy-related T/myeloid mixed phenotype acute leukemia t-MPAL.

Long term side effects of adjuvant chemotherapy in patients with early breast cancer.

Adjuvant systemic therapy along with screening has been key to the observed improvements in disease-free and overall survival (DFS/OS) in breast cancer. Improvements in overall survival already take into account therapy related toxicities that can result in death. However, this measure alone does not adequately capture the impact on health-related quality of life. Therefore, it is important to examine the prevalence, frequency and short/long-term impact of therapy-related toxicities, identify patients who might be at greatest risk. Ultimately decisions regarding expected therapy benefits (relative and absolute percentage improvements in DFS/OS) must be made against a background of known potential harms. For many patients with early breast cancer (EBC), their risk of recurrence is not zero but is small. At the same time, for many therapies for early stage breast cancer, the risk of serious side effects is small but is not zero. As we better understand the long-term side effects of adjuvant chemotherapy and targeted therapy, it becomes critical to integrate our growing understanding of breast cancer biology with standard high-quality histopathologic measures to better identify the patients most likely to benefit from the various options for combined multimodality therapy. Hence, we must strive against the notion of recommending adjuvant systemic chemotherapy "just in case." This article focuses on the long-term side effects of adjuvant chemotherapy in patients with EBC.

Methotrexate induced apoptotic and necrotic chromatin changes in rat myeloid leukemia cells.

OBJECTIVE: It was tested as to why low-dose methotrexate (MTX) effective against rheumatoid arthritis poses considerable health risk at higher doses. METHODS: The tumorigenic potential of My1/De blast cells was followed by cytology and by the kinetics of (18)FDG uptake. The toxicity of MTX on chromatin condensation was compared to predictive normal intermediates of chromosome condensation in control cells. RESULTS: MTX below 0.1 µg/ml did not cause visible changes in interphase chromatin structure. At its lowest toxic concentration (0.1 µg/ml) chromatin margination was confined to the outer edge of the nucleus. Between 0.1 and 5 µg/ml concentrations apoptotic chromatin shrinkage correlated with the dose of MTX. Apoptosis was exerted in early S phase excluding the mitotic effect. At higher MTX concentrations (>10 µg/ml) necrotic disruption and expansion took place. The lowest necrotic concentration (10 µg/ml) was close to highest apoptotic MTX concentration (5 µg/ml). CONCLUSIONS: The switch from apoptosis to inflammatory necrosis taking place within a narrow concentration range supports the notion of a narrow therapeutic spectrum. Chromatin changes are early markers of genotoxicity at much lower concentrations than citogenetic changes in properly chosen sensitive cells.

Upper airway cancer, myeloid leukemia, and other cancers in a cohort of British chemical workers exposed to formaldehyde.

The International Agency for Research on Cancer controversially has classified formaldehyde as causing nasopharyngeal carcinoma and myeloid leukemia. To provide further information on this question, we extended follow-up of a cohort of 14,008 chemical workers at 6 factories in England and Wales, covering the period 1941-2012. Mortality was compared with national death rates for England and Wales, and associations with incident upper airway cancer and leukemia were explored in nested case-control analyses. We observed excess deaths from cancers of the esophagus (100 observed vs. 93.1 expected), stomach (182 vs. 141.4), rectum (107 vs. 86.8), liver (35 vs. 26.9), and lung (813 vs. 645.8), but none of these tumors exhibited a clear exposure-response relationship. Nested case-control analyses of 115 men with upper airway cancer (including 1 nasopharyngeal cancer), 92 men with leukemia, and 45 men with myeloid leukemia indicated no elevations of risk in the highest exposure category (high exposure for ≥1 year). When the 2 highest exposure categories were combined, the odds ratio for myeloid leukemia was 1.26 (95% confidence interval: 0.39, 4.08). Our results provide no support for an increased hazard of myeloid leukemia, nasopharyngeal carcinoma, or other upper airway tumors from formaldehyde exposure. These results indicate that any excess risk of these cancers, even from relatively high exposures, is at most small.

Risk of myeloproliferative disease and chronic myeloid leukaemia following exposure to low-level benzene in a nested case-control study of petroleum workers.

BACKGROUND: Benzene exposure has been associated with increased risk of leukaemia and myelodysplastic syndrome. Existing studies are sparse for other lymphohaematopoietic cancer subtypes, such as myeloproliferative disease (MPD) and the related chronic myeloid leukaemia (CML). We pooled data from three petroleum worker nested case-control studies to address this gap. To our knowledge, this is the first study to systematically examine the relationship between MPD and quantitative benzene exposure. METHODS: There were 28 cases and 122 matched controls for CML and 30 MPD cases with 124 matched controls. Two haematopathologists identified each case and provided a diagnosis certainty score. Blinded data-driven assessments estimated benzene exposure for each job held by study participants. Statistical analyses included conditional logistic regression and penalised smoothing splines. RESULTS: Benzene exposures were low, and mean average exposure intensity for CML cases was 0.3 ppm and for MPD cases 0.17 ppm. Categorical analyses showed no increased risk of CML or MPD with benzene exposure. There was no significantly increased risk identified for more highly exposed terminal workers. Some association was seen in spline analyses between increased risk of MPD and benzene exposure experienced in the 2-20 years before diagnosis and with peak exposures considered with cumulative exposure as a continuous variable. CONCLUSIONS: No convincing association was identified between MPD or CML and low exposure to benzene. The greater risk for exposures experienced in the 20 years before diagnosis needs investigating in more powerful studies with a wider range of exposure to benzene, and the biological plausibility further examined from a mechanistic viewpoint.

Cohort mortality study of garment industry workers exposed to formaldehyde: update and internal comparisons.

BACKGROUND: To further evaluate the association between formaldehyde and leukemia, we extended follow-up through 2008 for a cohort mortality study of 11,043 US formaldehyde-exposed garment workers. METHODS: We computed standardized mortality ratios and standardized rate ratios stratified by year of first exposure, exposure duration, and time since first exposure. Associations between exposure duration and rates of leukemia and myeloid leukemia were further examined using Poisson regression models. RESULTS: Compared to the US population, myeloid leukemia mortality was elevated but overall leukemia mortality was not. In internal analyses, overall leukemia mortality increased with increasing exposure duration and this trend was statistically significant. CONCLUSIONS: We continue to see limited evidence of an association between formaldehyde and leukemia. However, the extended follow-up did not strengthen previously observed associations. In addition to continued epidemiologic research, we recommend further research to evaluate the biological plausibility of a causal relation between formaldehyde and leukemia.

Evolving risk of therapy-related acute myeloid leukemia following cancer chemotherapy among adults in the United States, 1975-2008.

Therapy-related acute myeloid leukemia (tAML) is a rare but highly fatal complication of cytotoxic chemotherapy. Despite major changes in cancer treatment, data describing tAML risks over time are sparse. Among 426068 adults initially treated with chemotherapy for first primary malignancy (9 US population-based cancer registries, 1975-2008), we identified 801 tAML cases, 4.70 times more than expected in the general population (P < .001). Over time, tAML risks increased after chemotherapy for non-Hodgkin lymphoma (n = 158; Poisson regression Ptrend < .001), declined for ovarian cancer (n = 72; Ptrend < .001), myeloma (n = 62; Ptrend = .02), and possibly lung cancer (n = 65; Ptrend = .18), and were significantly heterogeneous for breast cancer (n = 223; Phomogeneity = .005) and Hodgkin lymphoma (n = 58; Phomogeneity = .007). tAML risks varied significantly by age at first cancer and latency and were nonsignificantly heightened with radiotherapy for lung, breast, and ovarian cancers. We identified newly emerging elevated tAML risks in patients treated with chemotherapy since 2000 for esophageal, cervical, prostate, and possibly anal cancers; and since the 1990s for bone/joint and endometrial cancers. Using long-term, population-based data, we observed significant variation in tAML risk with time, consistent with changing treatment practices and differential leukemogenicity of specific therapies. tAML risks should be weighed against the benefits of chemotherapy, particularly for new agents and new indications for standard agents.

Stromal SPARC contributes to the detrimental fibrotic changes associated with myeloproliferation whereas its deficiency favors myeloid cell expansion.

In myeloid malignancies, the neoplastic clone outgrows normal hematopoietic cells toward BM failure. This event is also sustained by detrimental stromal changes, such as BM fibrosis and osteosclerosis, whose occurrence is harbinger of a dismal prognosis. We show that the matricellular protein SPARC contributes to the BM stromal response to myeloproliferation. The degree of SPARC expression in BM stromal elements, including CD146(+) mesenchymal stromal cells, correlates with the degree of stromal changes, and the severity of BM failure characterizing the prototypical myeloproliferative neoplasm primary myelofibrosis. Using Sparc(-/-) mice and BM chimeras, we demonstrate that SPARC contributes to the development of significant stromal fibrosis in a model of thrombopoietin-induced myelofibrosis. We found that SPARC deficiency in the radioresistant BM stroma compartment impairs myelofibrosis but, at the same time, associates with an enhanced reactive myeloproliferative response to thrombopoietin. The link betwen SPARC stromal deficiency and enhanced myeloid cell expansion under a myeloproliferative spur is also supported by the myeloproliferative phenotype resulting from the transplantation of defective Apc(min) mutant hematopoietic cells into Sparc(-/-) but not WT recipient BM stroma. Our results highlight a complex influence of SPARC over the stromal and hematopoietic BM response in myeloproliferative conditions.

Sole abnormalities of chromosome 7 in myeloid malignancies: spectrum, histopathologic correlates, and prognostic implications.

Among 6,565 consecutive abnormal cytogenetic reports at our institution, 3,192 (49%) constituted sole abnormalities, of which 230 (7%) involved chromosome 7: monosomy 7 (n = 98), 7q- (n = 51), der(1;7)(q10;p10) (n = 44), balanced translocations (n = 15), ring 7 (n = 13), and 7p- (n = 9). The most frequent histopathologic correlates were myelodysplastic syndromes (MDS; 28%), acute myeloid leukemia (AML; 17%), secondary or therapy-related MDS/AML (13%), primary myelofibrosis (PMF; 7%), and chronic myelomonocytic leukemia (6%). Monosomy 7 was the most frequent in each one of these disease categories except PMF where 7q- was more frequent. In primary MDS, patients with der(1;7)(q10;p10) (n = 13), compared to those with monosomy 7 (n = 30) or 7q- (n = 15), were less likely (P = 0.04) to display excess blasts or multilineage dysplasia but overall and leukemia-free survival adjusted for these variables revealed no significant difference between the three groups (P = 0.57 and 0.81, respectively). The current study does not prognostically distinguish monosomy 7 from 7q- or der(1;7), in MDS.

Formaldehyde and lymphohematopoietic cancers: a review of two recent studies.

OBJECTIVE: This paper reviews and evaluates two recent epidemiologic studies of formaldehyde exposure and lymphohematopoietic cancers. One is an update of mortality in a retrospective cohort study of industrial workers and the other is a proportional mortality and case-control study among embalmers. Both studies included subjects with considerable exposure to formaldehyde and both are focused on the myeloid leukemias. METHODS: The principal epidemiologic methods and analyses used in the studies are described and evaluated. Additional measures of risk are presented. RESULTS: Neither study reports a significant excess of mortality from any form of lymphohematopoietic cancer. However, both studies are interpreted by their authors as positive for an association between formaldehyde and the myeloid leukemias. This is based on weak and transitory associations seen in exposure-response analyses of relative risks. Issues are raised relating to the interpretation of these findings. CONCLUSION: There is no statistically significant absolute excess mortality from any lymphohematopoietic cancer in either study. The study of industrial workers showed only a weak and transitory relationship between peak exposure to formaldehyde and the myeloid leukemias. Limited exposure-response relationships for the myeloid leukemias in the case-control study of embalmers apparently have not been analyzed for statistical significance. These limited exposure-response relationships do not provide clear evidence of a causal relationship between formaldehyde and the myeloid leukemias.

Screening for clonal hematopoiesis as a predictive marker for development of therapy-related myeloid neoplasia (t-MN) following neoadjuvant therapy for breast cancer: a Southwest Oncology Group study (S0012).

A serious complication associated with breast cancer treatment is the increased risk for development of therapy-related myeloid neoplasms (t-MN). To determine whether dose-intensive adjuvant regimens for breast cancer induce genetic damage to hematopoietic stem cells, defined by the emergence of clonal hematopoiesis, and whether detection of clonal hematopoiesis could be used as an early marker for the subsequent development of t-MN, the Southwest Oncology Group designed a pilot clonality investigation to estimate the incidence of clonal hematopoiesis during and shortly after completion of the dose intensive neoadjuvant regimens for high-risk breast cancer patients. Peripheral blood samples from 274 patients obtained prior to treatment, at time of surgery, and at 6 and 12 months post-surgery were examined by two different clonality assays: the HUMARA (HUMan Androgen Receptor) assay to estimate the incidence of early genetic damage by clonal proliferation, and microsatellite instability (MSI) testing to screen for LOH or defective DNA mismatch repair mechanisms. Clonal hematopoiesis was negative in 93.5% of the samples analyzed. Five patients showed a HUMARA-positive/MSI-negative pattern, and no patients showed a HUMARA-negative/MSI-positive pattern. With a median follow-up of 3.1 years, one patient in our study developed t-AML at 3 years 5 months after randomization. Our results indicate that clonal hematopoiesis assays performed within the 2 years following dose-intensive neoadjuvant therapy failed to identify an emerging clonal hematopoietic stem cell population. Longer clinical follow-up will be necessary to define better the positive predictive value of detecting clonal hematopoiesis in the HUMARA+/MSI- cases.

MDM2 SNP309 and TP53 Arg72Pro interact to alter therapy-related acute myeloid leukemia susceptibility.

The p53 tumor suppressor directs the cellular response to many mechanistically distinct DNA-damaging agents and is selected against during the pathogenesis of therapy-related acute myeloid leukemia (t-AML). We hypothesized that constitutional genetic variation in the p53 pathway would affect t-AML risk. Therefore, we tested associations between patients with t-AML (n = 171) and 2 common functional p53-pathway variants, the MDM2 SNP309 and the TP53 codon 72 polymorphism. Although neither polymorphism alone influenced the risk of t-AML, an interactive effect was detected such that MDM2 TT TP53 Arg/Arg double homozygotes, and individuals carrying both a MDM2 G allele and a TP53 Pro allele, were at increased risk of t-AML (P value for interaction is .009). This interactive effect was observed in patients previously treated with chemotherapy but not in patients treated with radiotherapy, and in patients with loss of chromosomes 5 and/or 7, acquired abnormalities associated with prior exposure to alkylator chemotherapy. In addition, there was a trend toward shorter latency to t-AML in MDM2 GG versus TT homozygotes in females but not in males, and in younger but not older patients. These data indicate that the MDM2 and TP53 variants interact to modulate responses to genotoxic therapy and are determinants of risk for t-AML.

Translocation-positive acute myeloid leukemia associated with valproic acid therapy.

Valproic acid is an effective anti-epileptic medication often used for long-term control of seizure disorders that has been implicated in hematological toxicities, including rare reports of myelodysplasia and acute leukemia. Here, we report a case of valproic acid-related leukemia-like syndrome with a t(8;16) chromosomal translocation. After discontinuing valproic acid, the hematological findings completely resolved.