Acute leukemia as a secondary malignancy in children and adolescents: current findings and issues

Acute monocytic leukemia with KMT2A::LASP1 developed 9 months after diagnosis of acute megakaryoblastic leukemia in a 2-year-old boy

Acute myeloid leukemia (AML) is known as one of the subsequent malignant neoplasms that can develop after cancer treatment, but it is difficult to distinguish from relapse when the preceding cancer is leukemia. We report a 2-year-old boy who developed acute megakaryoblastic leukemia (AMKL, French-American-British classification [FAB]: M7) at 18 months of age and achieved complete remission with multi-agent chemotherapy without hematopoietic stem cell transplantation. Nine months after diagnosis and 4 months after completing treatment for AMKL, he developed acute monocytic leukemia (AMoL) with the KMT2A::LASP1 chimeric gene (FAB: M5b). The second complete remission was achieved using multi-agent chemotherapy and he underwent cord blood transplantation 4 months after AMoL was diagnosed. He is currently alive and disease free at 39 and 48 months since his AMoL and AMKL diagnoses, respectively. Retrospective analysis revealed that the KMT2A::LASP1 chimeric gene was detected 4 months after diagnosis of AMKL. Common somatic mutations were not detected in AMKL or AMoL and no germline pathogenic variants were detected. Since the patient's AMoL was different from his primary leukemia of AMKL in terms of morphological, genomic, and molecular analysis, we concluded that he developed a subsequent leukemia rather than a relapse of his primary leukemia.

Secondary Malignancies after Ewing Sarcoma-Epidemiological and Clinical Analysis of an International Trial Registry

Ewing sarcoma (EwS) represents highly aggressive bone and soft tissue tumors that require intensive treatment by multi-chemotherapy, surgery and/or radiotherapy. While therapeutic regimens have increased survival rates, EwS survivors face long-term sequelae that include secondary malignant neoplasms (SMNs). Consequently, more knowledge about EwS patients who develop SMNs is needed to identify high-risk patients and adjust follow-up strategies. We retrospectively analyzed data from 4518 EwS patients treated in five consecutive EwS trials from the Cooperative Ewing Sarcoma Study (CESS) group. Ninety-six patients developed SMNs after primary EwS, including 53 (55.2%) with solid tumors. The latency period between EwS and the first SMN was significantly longer for the development of solid SMNs (median: 8.4 years) than for hematologic SMNs (median: 2.4 years) (p < 0.001). The cumulative incidence (CI) of SMNs in general increased over time from 0.04 at 10 years to 0.14 at 30 years; notably, the specific CI for hematologic SMNs remained stable over the different decades, whereas for solid SMNs it gradually increased over time and was higher for metastatic patients than in localized EwS patients (20 years: 0.14 vs. 0.06; p < 0.01). The clinical characteristics of primary EwS did not differ between patients with or without SMNs. All EwS patients received multi-chemotherapy with adjuvant radiotherapy in 77 of 96 (80.2%) patients, and the use of radiation doses ≥ 60 Gy correlated with the occurrence of SMNs. The survival rate after SMNs was 0.49, with a significantly better outcome for solid SMNs compared with hematologic SMNs (3 years: 0.70 vs. 0.24, respectively; p < 0.001). The occurrence of SMNs after EwS remains a rare event but requires a structured follow-up system because it is associated with high morbidity and mortality.

Novel insights on [1,2]oxazolo[5,4-e]isoindoles on multidrug resistant acute myeloid leukemia cell line

A series of [1,2]oxazolo[5,4-e]isoindole derivatives was evaluated against HL-60 cell line and its multidrug resistance (MDR) variant, HL-60R, resistant to doxorubicin and to other P-gp substrates by overexpressing the efflux pump. They displayed antiproliferative activities, with IC50 values ranging from 0.02 to 5.5 µM. In particular, the newly synthesized compound 4k produced synergistic effects in terms of cell growth inhibition and cell death induction either in combination with a Vinca alkaloid, Vinblastine, and a Taxane, Paclitaxel in HL-60R cells. The study of the mechanism of action indicated that all compounds showed antimitotic activity through inhibition of tubulin polymerization. Thus, [1,2]oxazoles could represent a valuable tool to overcome MDR mechanism, confirming the potential use of this class of compounds.

Identification of a Unique Cytotoxic Thieno[2,3-c]Pyrazole Derivative with Potent and Selective Anticancer Effects In Vitro

In recent years, the thienopyrazole moiety has emerged as a pharmacologically active scaffold with antitumoral and kinase inhibitory activity. In this study, high-throughput screening of 2000 small molecules obtained from the ChemBridge DIVERset library revealed a unique thieno[2,3-c]pyrazole derivative (Tpz-1) with potent and selective cytotoxic effects on cancer cells. Compound Tpz-1 consistently induced cell death at low micromolar concentrations (0.19 μM to 2.99 μM) against a panel of 17 human cancer cell lines after 24 h, 48 h, or 72 h of exposure. Furthermore, an in vitro investigation of Tpz-1's mechanism of action revealed that Tpz-1 interfered with cell cycle progression, reduced phosphorylation of p38, CREB, Akt, and STAT3 kinases, induced hyperphosphorylation of Fgr, Hck, and ERK 1/2 kinases, and disrupted microtubules and mitotic spindle formation. These findings support the continued exploration of Tpz-1 and other thieno[2,3-c]pyrazole-based compounds as potential small-molecule anticancer agents.

Therapy-related Myeloid Neoplasms in Children: A Single-institute Study

Therapy-related myeloid neoplasm (t-MN) in the pediatric population is not well characterized. We studied 12 pediatric patients diagnosed with t-MN in our institution since 2006. The median age at the t-MN diagnoses was 14.8 years (range, 9 to 20 y). The primary malignancies included 9 solid tumors and 3 hematopoietic malignancies. Rhabdomyosarcoma (n=4) was the most common primary malignancy. Five of the 9 patients with solid tumors and all 3 patients with hematopoietic malignancies had primary neoplasms involving bone marrow. The median latency period was 5.2 years (range, 1.8 to 13.8 y). Thrombocytopenia was present in all patients at the t-MN diagnoses. Complete or partial monosomy of chromosome 5 or 7 were the 2 most common cytogenetic abnormalities. A quarter of patients demonstrated a genetic predisposition to t-MN: 1 with Li-Fraumeni syndrome with a germline TP53 R248Q mutation, 1 with Noonan syndrome with a somatic mutation (PTPN11 S502T), and 1 with a constitutive chromosomal translocation [t(X;9)(p22;q34)] and a germline TP53 L130V mutation. Outcomes remain poor. Two patients survived 3 and 5.1 years after hematopoietic stem cell transplantation.

KMT2A-MAML2 rearrangement emerged and regressed during neuroblastoma therapy without leukemia after 12.8-year follow-up

Twelvepatients without therapy-related leukemia were studied after completing TOP2 poison chemotherapy in a high-risk neuroblastoma regimen. One patient harbored an inv(11) that was a KMT2A rearrangement. The KMT2A-MAML2 transcript was expressed at low level. The patient was prospectively followed. The inv(11) was undetectable in ensuing samples. Leukemia never developed after a 12.8-year follow-up period. Enriched etoposide-induced TOP2A cleavage in the relevant MAML2 genomic region supports a TOP2A DNA damage mechanism. After completing TOP2 poison chemotherapies, covert KMT2A-R clones may occur in a small minority of patients; however, not all KMT2A rearrangements herald a therapy-related leukemia diagnosis.

Mutagenic Consequences of Sublethal Cell Death Signaling

Many human cancers exhibit defects in key DNA damage response elements that can render tumors insensitive to the cell death-promoting properties of DNA-damaging therapies. Using agents that directly induce apoptosis by targeting apoptotic components, rather than relying on DNA damage to indirectly stimulate apoptosis of cancer cells, may overcome classical blocks exploited by cancer cells to evade apoptotic cell death. However, there is increasing evidence that cells surviving sublethal exposure to classical apoptotic signaling may recover with newly acquired genomic changes which may have oncogenic potential, and so could theoretically spur the development of subsequent cancers in cured patients. Encouragingly, cells surviving sublethal necroptotic signaling did not acquire mutations, suggesting that necroptosis-inducing anti-cancer drugs may be less likely to trigger therapy-related cancers. We are yet to develop effective direct inducers of other cell death pathways, and as such, data regarding the consequences of cells surviving sublethal stimulation of those pathways are still emerging. This review details the currently known mutagenic consequences of cells surviving different cell death signaling pathways, with implications for potential oncogenic transformation. Understanding the mechanisms of mutagenesis associated (or not) with various cell death pathways will guide us in the development of future therapeutics to minimize therapy-related side effects associated with DNA damage.

Hematologic indices in individuals with pathogenic germline DICER1 variants

Pathogenic germline variants in DICER1 underlie an autosomal dominant, pleiotropic tumor-predisposition disorder. Murine models with the loss of DICER1 in hematopoietic stem cell progenitors demonstrate hematologic aberrations that include reductions in red and white blood cell counts, hemoglobin volume, and impaired maturation resulting in dysplasia. We investigated whether hematologic abnormalities such as those observed in DICER1-deficient mice were observed in humans with a pathogenic germline variant in DICER1. A natural history study of individuals with germline pathogenic DICER1 variants and family controls conducted through the National Cancer Institute (NCI) evaluated enrollees at the National Institutes of Health Clinical Center during a comprehensive clinical outpatient visit that included collecting routine clinical laboratory studies. These were compared against normative laboratory values and compared between the DICER1 carriers and controls. There were no statistical differences in routine clinical hematology laboratory studies observed in DICER1 carriers and family controls. A review of the medical history of DICER1 carriers showed that none of the individuals in the NCI cohort developed myelodysplastic syndrome or leukemia. Query of the International Pleuropulmonary Blastoma/DICER1 Registry revealed 1 DICER1 carrier who developed a secondary leukemia after treatment of pleuropulmonary blastoma. We found limited evidence that the hematologic abnormalities observed in murine DICER1 models developed in our cohort of DICER1 carriers. In addition, no cases of myelodysplastic syndrome were observed in either the NCI cohort or the International Pleuropulmonary Blastoma/DICER1 Registry; 1 case of presumed secondary leukemia was reported. Abnormalities in hematologic indices should not be solely attributed to DICER1. This trial was registered at www.clinicaltrials.gov as #NCT01247597.

Role of radiotherapy and chemotherapy in the risk of leukemia after childhood cancer: An international pooled analysis

Childhood cancer survivors are at increased risk for second primary leukemia (SPL), but there is little consensus on the magnitude of some risk factors because of the small size of previous studies. We performed a pooled analysis of all published studies with detailed treatment data, including estimated active bone marrow (ABM) dose received during radiation therapy and doses of specific chemotherapeutic agents for childhood cancer diagnosed from 1930 through 2000, in order to more thoroughly investigate treatment-related risks of SPL. A total of 147 SPL cases (of which 69% were acute myeloid leukemia [AML]) were individually matched to 522 controls, all from four case-control studies including patients from six countries (France, United Kingdom, United States, Canada, Italy and Netherlands). Odds ratios (OR) and corresponding 95% confidence intervals (CIs) were calculated using conditional logistic regression, and the excess OR per Gray (EOR/Gy) was also calculated. After accounting for the other therapies received, topoisomerase II inhibitor was associated with an increased SPL risk (highest tertile vs none: OR = 10.0, 95% CI: 3.7-27.3). Radiation dose to the ABM was also associated with increased SPL risk among those not receiving chemotherapy (EOR/Gy = 1.6, 95% CI: 0.1-14.3), but not among those who received chemotherapy (CT). SPL were most likely to occur in the first decade following cancer treatment. Results were similar when analyses were restricted to AML. The evidence of interaction between radiation and CT has implications for leukemogenic mechanism. The results for topoisomerase II inhibitors are particularly important given their increasing use to treat childhood cancer.

Characterization of myelodysplastic syndromes progressing to acute lymphoblastic leukemia

Myelodysplastic syndromes (MDS) are a heterogeneous group of diseases, with a variable probability of transformation into acute leukemia, which is, in the vast majority of cases, of myeloid lineage. Nevertheless, rare cases of acute lymphoblastic leukemia in patients with previously diagnosed MDS have been reported. We describe a series of 3 cases of MDS/CMML marked with evolution to acute lymphoblastic leukemia (ALL) and provide a comprehensive review of the 49 cases documented in the literature so far. These sporadic events have only been published as single-case reports or small series to date. Such atypical cases emphasize the possibility of major phenotypic switches arising at the leukemic stem cell (LSC) and/or early progenitor levels, as a consequence of epigenetic and genomic events driving these changes in the bone marrow niche.

Epidemiology and Etiology of Leukemia and Lymphoma

Available evidence suggests that the incidence of leukemia and lymphoma tends to be higher in highly developed regions of the world and among Whites in the United States. Temporal trends in incidence are dynamic and multifactorial; for instance, the incidence of non-Hodgkin's lymphoma increased around the turn of the century, in part because of the acquired immune deficiency syndrome (AIDS) epidemic. Most leukemias and lymphomas are sporadic and the specific etiology remains elusive. Still, research shows that these malignancies often develop in the context of genetic abnormalities, immunosuppression, and exposure to risk factors like ionizing radiation, carcinogenic chemicals, and oncogenic viruses. The prognosis varies by subtype, with poorer survival outcomes for acute leukemias among adults, and more favorable outcomes for Hodgkin's lymphoma. At a time when specific prevention efforts targeting these malignancies are nonexistent, there is a great need to ensure equitable access to diagnostic services and treatments worldwide.

Risk of Leukemia after Dengue Virus Infection: A Population-Based Cohort Study

BACKGROUND

Infections account for about 15% of human cancers globally. Although abnormal hematologic profiles and bone marrow suppression are common in patients with dengue, whether dengue is associated with a higher risk of leukemia has not been investigated.

METHODS

We conducted a nationwide population-based cohort study by analyzing the National Health Insurance Research Databases in Taiwan. Laboratory-confirmed dengue patients between 2002 and 2011 were identified; five matched non-dengue controls were randomly selected for each patient. Follow-up ended on December 31, 2015. Multivariate Cox proportional hazard regression models were used to evaluate the effect of dengue virus infection on the risk of leukemia. Cancers other than leukemia were used as falsification endpoints to evaluate the validity of this study.

RESULTS

We identified 12,573 patients with dengue and 62,865 non-dengue controls. Patients with dengue had a higher risk of leukemia [adjusted HR, 2.03; 95% confidence interval (CI), 1.16-3.53]. Stratified analyses by different follow-up periods showed that dengue virus infection was significantly associated with a higher risk of leukemia only between 3 and 6 years after infection (adjusted HR, 3.22; 95% CI, 1.25-8.32). There was no significant association between dengue and the risk of other cancers.

CONCLUSIONS

This study provides the first epidemiologic evidence for the association between dengue virus infection and leukemia.

IMPACT

Considering the rapidly increasing global incidence of dengue and the burden of leukemia, further studies are required to verify this association and to unravel the potential mechanisms of pathogenesis.

Drug Repurposing for Retinoblastoma: Recent Advances

Retinoblastoma is the intraocular malignancy that occurs during early childhood. The current standard of care includes chemotherapy followed by focal consolidative therapies, and enucleation. Unfortunately, these are associated with many side and late effects. New drugs and/or drug combinations need to be developed for safe and effective treatment. This compelling need stimulated efforts to explore drug repurposing for retinoblastoma. While conventional drug development is a lengthy and expensive process, drug repurposing is a faster, alternate approach, where an existing drug, not meant for treating cancer, can be repurposed to treat retinoblastoma. The present article reviews various attempts to test drugs approved for different purposes such as calcium channels blockers, non-steroidal antiinflammatory drugs, cardenolides, antidiabetic, antibiotics and antimalarial for treating retinoblastoma. It also discusses other promising candidates that could be explored for repurposing for retinoblastoma.

Development of acute lymphoblastic leukemia following treatment for acute myeloid leukemia in children with Down syndrome: A case report and retrospective review of Children's Oncology Group acute myeloid leukemia trials

Children with Down syndrome have a 150-fold increased risk of developing acute myeloid leukemia (AML) and 20-fold increased risk of developing acute lymphoblastic leukemia (ALL). Although the risk of developing AML and ALL is significantly increased in children with Down syndrome, the development of both malignancies in the same patient is very rare. We describe a patient with Down syndrome who developed ALL 6 years after being diagnosed with AML. We performed a literature review and Children's Oncology Group query and discovered eight published cases and five cases of ALL following AML in pediatric patients with Down syndrome, as well as six cases of ALL following AML in non-Down syndrome patients. There was a similar cumulative incidence of ALL after treatment for AML in the Down syndrome and non-Down syndrome populations. Overall survival in patients with Down syndrome who developed ALL after treatment for AML was comparable to overall survival for patients with Down syndrome with de novo ALL with an average follow-up of 7 years after ALL diagnosis. Clinical data collected were used to discuss whether this phenomenon represents a secondary leukemia, second primary cancer, or mixed-lineage leukemia.

Caring for survivors of childhood cancer: it takes a village

PURPOSE OF REVIEW

Over 80% of children diagnosed with cancer are now cured. The burgeoning population of survivors of childhood cancer experiences high rates of morbidity and mortality due to 'late-effects' of treatment. These can be defined as any consequence of treatment that persists beyond or develops after the completion of cancer therapy. Awareness of late-effects is critically important for pediatricians and adult providers alike, as late-effects impact children in proximity to cancer treatment, as well as adults many decades removed. This review presents the importance of lifelong follow-up care for survivors, highlights existing screening guidelines, and reviews various models of survivor care.

RECENT FINDINGS

National and international guidelines have been developed to standardize screening for survivors, and multiple models of survivorship care exist. The optimal model likely depends on individual factors, including the survivor's needs and preferences, as well as local resources. Key strategies for the successful care of survivors include accurate risk-stratification for specific late-effects, individualized screening plans, education of survivors and professionals, clear communication between providers, and well coordinated transition of care across services.

SUMMARY

Early identification and management of late-effects are important for survivors of childhood cancer. Providers should be familiar with the risks for specific late-effects and have access to screening guidelines. The strengths and weaknesses of care models, along with individual circumstances, should be considered in designing the optimal approach to care for each survivor.

Targeting EIF4E signaling with ribavirin in infant acute lymphoblastic leukemia

The poor outcomes in infant acute lymphoblastic leukemia (ALL) necessitate new treatments. Here we discover that EIF4E protein is elevated in most cases of infant ALL and test EIF4E targeting by the repurposed antiviral agent ribavirin, which has anticancer properties through EIF4E inhibition, as a potential treatment. We find that ribavirin treatment of actively dividing infant ALL cells on bone marrow stromal cells (BMSCs) at clinically achievable concentrations causes robust proliferation inhibition in proportion with EIF4E expression. Further, we find that ribavirin treatment of KMT2A-rearranged (KMT2A-R) infant ALL cells and the KMT2A-AFF1 cell line RS4:11 inhibits EIF4E, leading to decreases in oncogenic EIF4E-regulated cell growth and survival proteins. In ribavirin-sensitive KMT2A-R infant ALL cells and RS4:11 cells, EIF4E-regulated proteins with reduced levels of expression following ribavirin treatment include MYC, MCL1, NBN, BCL2 and BIRC5. Ribavirin-treated RS4:11 cells exhibit impaired EIF4E-dependent nuclear to cytoplasmic export and/or translation of the corresponding mRNAs, as well as reduced phosphorylation of the p-AKT1, p-EIF4EBP1, p-RPS6 and p-EIF4E signaling proteins. This leads to an S-phase cell cycle arrest in RS4:11 cells corresponding to the decreased proliferation. Ribavirin causes nuclear EIF4E to re-localize to the cytoplasm in KMT2A-AFF1 infant ALL and RS4:11 cells, providing further evidence for EIF4E inhibition. Ribavirin slows increases in peripheral blasts in KMT2A-R infant ALL xenograft-bearing mice. Ribavirin cooperates with chemotherapy, particularly L-asparaginase, in reducing live KMT2A-AFF1 infant ALL cells in BMSC co-cultures. This work establishes that EIF4E is broadly elevated across infant ALL and that clinically relevant ribavirin exposures have preclinical activity and effectively inhibit EIF4E in KMT2A-R cases, suggesting promise in EIF4E targeting using ribavirin as a means of treatment.

Continued Tumor Reduction of Metastatic Pheochromocytoma/Paraganglioma Harboring Succinate Dehydrogenase Subunit B Mutations with Cyclical Chemotherapy

Patients harboring germline mutations in the succinate dehydrogenase complex subunit B (SDHB) gene present with pheochromocytomas and paragangliomas (PPGL) that are more likely malignant and clinically aggressive. The combination chemotherapy cyclophosphamide, vincristine, and dacarbazine (CVD) was retrospectively evaluated in patients with SDHB-associated metastatic PPGL.Query Twelve metastatic PPGL patients harboring SDHB mutations/polymorphisms with undetectable SDHB immunostaining were treated with CVD. CVD therapy consisted of 750 mg/m² cyclophosphamide with 1.4 mg/m² vincristine on day 1 and 600 mg/m² dacarbazine on days 1 and 2, every 21-28 days. Treatment outcome was determined by RECIST criteria as well as determination of response duration and progression-free and overall survivals. A median of 20.5 cycles (range 4-41) was administered. All patients had tumor reduction (12-100% by RECIST). Complete response was seen in two patients, while partial response was observed in 8. The median number of cycles to response was 5.5. Median duration of response was 478 days, with progression-free and overall survivals of 930 and 1190 days, respectively. Serial [¹⁸F]-fluorodeoxyglucose positron emission tomography and computed tomography imaging demonstrated continued incremental reduction in maximal standardized uptake values (SUV_max) values in 26/30 lesions. During treatment administration, the median SUV decreased from > 25 to < 6, indicating the efficacy of chemotherapy over a prolonged period of time. Prolonged therapy results in continued incremental tumor reduction, and is consistent with persistent drug sensitivity. CVD chemotherapy is recommended to be considered part of the initial management in patients with metastatic SDHB-related PPGL.

Second Neoplasms in Children Following a Treatment for Acute Leukemia and/or Lymphoma: 29 Years of Experience in a Single Institution in Argentina

INTRODUCTION

Childhood acute leukemias (AL) and lymphomas achieve good survival rates. However, second neoplasms (SN) are a devastating event.

METHODS

From August 1987 to December 2016, 34 of 3321 (1%) patients with diagnosis of AL or lymphoma developed SN. SN were AL (n=16), CNS tumors (n=5), endocrinal tumors (n=3), lymphomas (n=2), schwannoma (n=2) assorted sarcomas (n=4), retinal melanoma (n=1), and Vanek tumor (n=1). Median latency was 51 (range, 10 to 110) months for hematological malignancies and 119 (range, 25 to 236) months for solid tumors (P=0.001).

RESULTS

A total of 33 patients with SN were treated taking into account cumulative doses of anthracyclines and radiotherapy. Twenty-three (67.6%) patients achieved complete remission (CR), 5 died early during therapy and 5 were refractory or partial responders. Six patients presented relapses of the SN and 1 died in CR. Seventeen patients remain alive in CR, with a median follow-up of 110 (range, 4 to 276) months.

CONCLUSIONS

(1) The latency period was significantly longer for patients developing solid tumors than for those developing AL. (2) AL was the most frequent SN. (3) Our results strongly encourage giving standard therapy to SN, considering cumulative doses of previous treatment, since similar probabilities of surviving as "de novo" counterparts can be achieved.

Development of Secondary Acute Myeloid Leukemia in a Pediatric Patient Concurrently Receiving Primary Therapy for Ewing Sarcoma

Ewing sarcoma is a pediatric bone and soft tissue sarcoma that requires intensive therapy, which can cause secondary malignancies. We present a rare case of early, treatment-related AML in a pediatric patient concurrently receiving primary therapy for Ewing sarcoma. Despite AML-directed therapy, our patient died secondary to complications of hyperleukocytosis. Cytogenetic and mutation profiling of the leukemia cells revealed the DNA-topoisomerase-II-inhibitor-associated t(9;11)(p22;q23) translocation and clonal KRAS and BRAF mutations. This report highlights the importance of monitoring for treatment-related effects in cancer therapy, as well as the need for novel, less toxic approaches in Ewing sarcoma therapy.

Acute lymphoblastic leukemia in patients with Down syndrome with a previous history of acute myeloid leukemia

Patients with Down syndrome (DS) are predisposed to acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) in early and later childhood, respectively, but rarely experience both. We herein discuss four patients with DS with ALL and a history of AML who were treated with various chemotherapies, one of whom later received a bone marrow transplantation. Three patients survived and remain in remission. One patient died of fulminant hepatitis during therapy. No common cytogenetic abnormalities in AML and ALL besides constitutional +21 were identified, indicating that the two leukemia types were independent events. However, the underlying pathomechanism of these conditions awaits clarification.

Methodological choices affect cancer incidence rates: a cohort study

Background

Incidence rates are fundamental to epidemiology, but their magnitude and interpretation depend on methodological choices. We aimed to examine the extent to which the definition of the study population affects cancer incidence rates.

Methods

All primary cancer diagnoses in Sweden between 1958 and 2010 were identified from the national Cancer Register. Age-standardized and age-specific incidence rates of 29 cancer subtypes between 2000 and 2010 were calculated using four definitions of the study population: persons resident in Sweden 1) based on general population statistics; 2) with no previous subtype-specific cancer diagnosis; 3) with no previous cancer diagnosis except non-melanoma skin cancer; and 4) with no previous cancer diagnosis of any type. We calculated absolute and relative differences between methods.

Results

Age-standardized incidence rates calculated using general population statistics ranged from 6% lower (prostate cancer, incidence rate difference: -13.5/100,000 person-years) to 8% higher (breast cancer in women, incidence rate difference: 10.5/100,000 person-years) than incidence rates based on individuals with no previous subtype-specific cancer diagnosis. Age-standardized incidence rates in persons with no previous cancer of any type were up to 10% lower (bladder cancer in women) than rates in those with no previous subtype-specific cancer diagnosis; however, absolute differences were <5/100,000 person-years for all cancer subtypes.

Conclusions

For some cancer subtypes incidence rates vary depending on the definition of the study population. For these subtypes, standardized incidence ratios calculated using general population statistics could be misleading. Moreover, etiological arguments should be used to inform methodological choices during study design.

Electronic supplementary material

The online version of this article (doi:10.1186/s12963-017-0120-x) contains supplementary material, which is available to authorized users.

Secondary cancers after a childhood cancer diagnosis: a nationwide hospital-based retrospective cohort study in Japan

BACKGROUND

The epidemiology of secondary cancers in childhood cancer survivors has been unknown in Asian countries. Our aim is to assess the incidence and risk factors for secondary cancers through a nationwide survey in Japan.

METHODS

A retrospective cohort study comprising 10,069 children who were diagnosed with cancer between 1980 and 2009 was conducted in 15 Japanese hospitals. The cumulative incidence rate was calculated using death as the competing risk and compared by the Gray method. The standardized incidence ratio (SIR) was defined as the ratio of the number of observed cancers divided by the number of expected cancers. The risk factors were analyzed using Cox regression analysis.

RESULTS

One hundred and twenty-eight patients (1.3 %) developed secondary cancers within a median follow-up of 8.4 years. The cumulative incidence rate was 1.1 % (95 % confidence interval [CI] 0.9-1.4) at 10 years and 2.6 % (95 % CI 2.1-3.3) at 20 years after primary cancer diagnosis. Sensitivity analysis, limited to 5-year survivors (n = 5,387), confirmed these low incidence rates. The SIR of secondary cancers was 12.1 (95 % CI 10.1-14.4). In the Cox analysis, the hazard ratios for secondary cancers were 3.81 (95 % CI 1.53-9.47) for retinoblastoma, 2.78 (95 % CI 1.44-5.38) for bone/soft tissue sarcomas, and 1.81 (95 % CI 1.16-2.83) for allogeneic stem cell transplantation.

CONCLUSIONS

The cumulative incidence of secondary cancers in children in Japan was not high; however, the SIR was relatively high. Retinoblastoma or sarcoma in addition to allogeneic stem cell transplantation were significant risk factors for secondary cancers.

Childhood Exposures and Risk of Malignancy in Adulthood

Pediatricians have significant roles in preventive health care, and understanding how various exposures during childhood can have long-lasting effects on cancer risk is critical in promoting future health. With the exception of rare genetic syndromes conferring increased cancer susceptibility, most cancers are considered idiopathic and may be influenced by modifiable exposures and risks. This review aims to serve as a brief overview of a subset of known exposures during childhood that have been associated with an increased risk of malignancy in adulthood, including the effects of radiation, chemotherapy, pesticides, nutrition, puberty, and infection.

Hematopoietic stem cell transplantation in adolescents and young adults

BACKGROUND

Adolescents and young adults (AYAs) are a very unique subset of our population journeying through a dynamic stage of their lives. This age group often remains understudied as a separate entity because they are commonly lumped into either pediatric or adult subgroups.

METHODS

Here we review acute and chronic issues surrounding hematopoietic stem cell transplantation (HSCT) with a focus on the AYA age group.

RESULTS

HSCT is a commonly used treatment modality for patients with certain types of cancers. AYA patients undergoing HSCT present a very unique perspective, circumstances, medical, psychological and social issues requiring a diligent workup, care and follow-up.

CONCLUSION

The medical care of these patients should be approached in a multidisciplinary method involving the patient, caregivers, physicians, psychologists and social workers.

Secondary malignant neoplasms after high-dose chemotherapy and autologous stem cell rescue for high-risk neuroblastoma

BACKGROUND

Outcomes for high-risk neuroblastoma remain poor. Modern treatment protocols utilizing intense induction followed by myeloablative consolidation chemotherapy with autologous stem cell rescue (ASCR) have improved survival rates, but the long-term sequelae, including development of secondary malignant neoplasms (SMN), are just now surfacing.

METHODS

We retrospectively reviewed data from 87 patients with high-risk neuroblastoma who were treated with intensive induction chemotherapy followed by ASCR between January 1991 and July 2011 following one of two institutional protocols: Chicago Pilot 1 (CP1; n = 12) and Chicago Pilot 2 (CP2; n = 75).

RESULTS

The 15-year overall survival rate for all 87 patients was 33.9% (95% confidence interval [CI], 23.1-45.0%). The 10- and 15-year cumulative incidence of SMN was 16.5% (95%CI, 7.2-38.0%) and 34.2% (95%CI, 18.6-63.1%), respectively, without evidence of a plateau at 15 years. Six of the 10 patients (n = 2 in CP1 and n = 8 in CP2) who developed SMN had hematologic malignancies including acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS). Solid tumors included thyroid papillary carcinoma, chondrosarcoma, hepatocellular carcinoma, and biliary adenocarcinoma.

CONCLUSION

A significantly higher incidence of SMN, especially hematological malignancies, was observed in this cohort compared to older neuroblastoma studies, potentially due to exposure to epipodophyllotoxins and a high cumulative dose of alkylating agents these patients received. The risk of developing an SMN continued to increase with survival time and did not reach the plateau at 15 years. Although the number of the patients is relatively small, our study emphasizes the need for life-long follow-up of survivors who were treated using modern therapy.

Secondary malignancies in pediatric cancer survivors: perspectives and review of the literature

With continuing improvements in the successful treatment of pediatric malignancies, long term survivors of pediatric cancers and their providers are faced with new oncologic issues regarding long-term morbidities. As pediatric cancer survivors have matured into adulthood, the development of secondary malignancies has become a significant issue for these patients. Whether a consequence of treatment for the patient's original cancer, such as chemotherapy, ionizing radiation, or hematopoietic stem cell transplantation, secondary malignancies now present patients and providers with new challenges regarding treatment, surveillance and counseling. We review the major risk factors for secondary malignancies in pediatric cancer survivors, with particular emphasis on important molecular and cytogenetic risk factors, both inherited and acquired. We conclude with a discussion of recommendations for surveillance and counseling of these patients.

Pharmacokinetics and efficacy of the spleen tyrosine kinase inhibitor r406 after ocular delivery for retinoblastoma

PURPOSE

Retinoblastoma is a childhood cancer of the retina. Clinical trials have shown that local delivery of broad spectrum chemotherapeutic agents is efficacious. Recent studies characterizing the genomic and epigenomic landscape of retinoblastoma identified spleen tyrosine kinase (SYK) as a promising candidate for targeted therapy. The purpose of this study was to conduct preclinical testing of the SYK antagonist R406 to evaluate it as a candidate for retinoblastoma treatment.

METHODS

The efficacy of the SYK antagonist R406 delivered locally in a human orthotopic xenograft mouse model of retinoblastoma was tested. Intraocular exposure of R406 was determined for various routes and formulations.

RESULTS

There was no evidence of efficacy for subconjunctival. R406. Maximal vitreal concentration was 10-fold lower than the minimal concentration required to kill retinoblastoma cells in vitro. Dosage of R406 subconjunctivally from emulsion or suspension formulations, direct intravitreal injection of the soluble prodrug of R406 (R788), and repeated topical administration of R406 all increased vitreal exposure, but failed to reach the exposure required for retinoblastoma cell death in culture.

CONCLUSION

Taken together, these data suggest that R406 is not a viable clinical candidate for the treatment of retinoblastoma. This study highlights the importance of pharmacokinetic testing of molecular targeted retinoblastoma therapeutics.

Lymphohematopoietic cancers induced by chemicals and other agents and their implications for risk evaluation: An overview

Lymphohematopoietic neoplasia are one of the most common types of cancer induced by therapeutic and environmental agents. Of the more than 100 human carcinogens identified by the International Agency for Research on Cancer, approximately 25% induce leukemias or lymphomas. The objective of this review is to provide an introduction into the origins and mechanisms underlying lymphohematopoietic cancers induced by xenobiotics in humans with an emphasis on acute myeloid leukemia, and discuss the implications of this information for risk assessment. Among the agents causing lymphohematopoietic cancers, a number of patterns were observed. Most physical and chemical leukemia-inducing agents such as the therapeutic alkylating agents, topoisomerase II inhibitors, and ionizing radiation induce mainly acute myeloid leukemia through DNA-damaging mechanisms that result in either gene or chromosomal mutations. In contrast, biological agents and a few immunosuppressive chemicals induce primarily lymphoid neoplasms through mechanisms that involve alterations in immune response. Among the environmental agents examined, benzene was clearly associated with acute myeloid leukemia in humans, with increasing but still limited evidence for an association with lymphoid neoplasms. Ethylene oxide and 1,3-butadiene were linked primarily to lymphoid cancers. Although the association between formaldehyde and leukemia remains controversial, several recent evaluations have indicated a potential link between formaldehyde and acute myeloid leukemia. The four environmental agents examined in detail were all genotoxic, inducing gene mutations, chromosomal alterations, and/or micronuclei in vivo. Although it is clear that rapid progress has been made in recent years in our understanding of leukemogenesis, many questions remain for future research regarding chemically induced leukemias and lymphomas, including the mechanisms by which the environmental agents reviewed here induce these diseases and the risks associated with exposures to such agents.

Secondary Leukemia After Chemotherapy and/or Radiotherapy for Gynecologic Neoplasia

Objective

Secondary leukemia is a known complication of chemotherapy and radiotherapy. It was generally recognized that leukemia secondary to chemotherapy was due to the use of alkylating agents in the treatment of ovarian cancer. Recently, many types of chemotherapeutic agents have been used in the treatment of gynecologic malignancies in addition to ovarian cancer. We analyzed the clinical characteristics and outcome of patients with recent onset of secondary leukemia after the treatment of gynecologic cancer to consider the diagnosis and management of secondary leukemia.

Materials and Methods

We reviewed the clinical charts and follow-up data of patients with gynecologic malignancies treated in the past 20 years. During this period, 2482 newly diagnosed invasive gynecologic cancers were treated in our institution. All patients with secondary leukemia were analyzed for clinical background, latency period (interval between the diagnosis of primary carcinoma and the development of leukemia), treatment, and outcome. We also reviewed the literature for secondary leukemia under gynecology using the PubMed.

Results

Four patients were found to have developed secondary leukemia after the treatment of gynecologic malignancies during this period. The cumulative risk of secondary leukemia was approximately 0.38%. All patients received platinum-based chemotherapy. Two patients received combination chemotherapy and/or bone marrow transplantation, and 1 of these 2 patients lived more than 6 years but died of recurrent ovarian cancer.

Conclusions

Long survival time might be expected in patients who show complete response to bone marrow transplantation and/or combination chemotherapy for secondary leukemia. In recent years, we have aggressively used various types of anticancer drugs for the treatment of not only ovarian cancer but also uterine cervical cancer and endometrial cancer. Physicians need to keep in mind the risk of secondary leukemia in the follow-up of long-term survivors after several courses of chemotherapy and radiotherapy.

Survivors of childhood and adolescent cancer: life-long risks and responsibilities

Survival rates for most paediatric cancers have improved at a remarkable pace over the past four decades. In developed countries, cure is now the probable outcome for most children and adolescents who are diagnosed with cancer: their 5-year survival rate approaches 80%. However, the vast majority of these cancer survivors will have at least one chronic health condition by 40 years of age. The burden of responsibility to understand the long-term morbidity and mortality that is associated with currently successful treatments must be borne by many, including the research and health care communities, survivor advocacy groups, and governmental and policy-making entities.

Autoimmune lymphoproliferative syndrome misdiagnosed as hemophagocytic lymphohistiocytosis

Autoimmune lymphoproliferative syndrome (ALPS) is a rare inherited disorder of apoptosis, most commonly due to mutations in the FAS (TNFRSF6) gene. It presents with chronic lymphadenopathy, splenomegaly, and symptomatic multilineage cytopenias in an otherwise healthy child. Unfortunately, these clinical findings are also noted in other childhood lymphoproliferative conditions, such as leukemia, lymphoma, and hemophagocytic lymphohistiocytosis, which can confound the diagnosis. This report describes a 6-year-old girl with symptoms misdiagnosed as hemophagocytic lymphohistiocytosis and treated with chemotherapy before the recognition that her symptoms and laboratory values were consistent with a somatic FAS mutation leading to ALPS. This case should alert pediatricians to include ALPS in the differential diagnosis of a child with lymphadenopathy, splenomegaly, and cytopenias; obtain discriminating screening laboratory biomarkers, such as serum vitamin B-12 and ferritin levels; and, in the setting of a highly suspicious clinical scenario for ALPS, pursue testing for somatic FAS mutations when germ-line mutation testing is negative.

Topoisomerase 2β: a promising molecular target for primary prevention of anthracycline-induced cardiotoxicity

Anthracyclines are powerful chemotherapy agents that are still widely used today. However, their clinical use is limited by the development of dose-dependent cardiotoxicity. Recently, we showed that topoisomerase 2β (Top2β) is required for anthracycline to induce DNA double-strand breaks and changes in the transcriptome, leading to mitochondrial dysfunction and generation of reactive oxygen species. Furthermore, deleting Top2β from cardiomyocytes prevented the development of anthracycline-induced cardiotoxicity in mice. On the basis of this molecular insight, new strategies should be developed to prevent anthracycline-induced cardiotoxicity. First, Top2α-specific anthracyclines should be tested to determine whether they will spare the heart. Second, Top2β should be studied as a potential biomarker to predict risk of developing cardiotoxicity before anthracycline treatment. Third, inhibiting and deleting Top2β in the heart should also be tested as primary prevention strategies. We propose that Top2β is a promising molecular target that can be used to design interventions to prevent anthracycline-induced cardiotoxicity.

Myc-driven overgrowth requires unfolded protein response-mediated induction of autophagy and antioxidant responses in Drosophila melanogaster

Autophagy, a lysosomal self-degradation and recycling pathway, plays dual roles in tumorigenesis. Autophagy deficiency predisposes to cancer, at least in part, through accumulation of the selective autophagy cargo p62, leading to activation of antioxidant responses and tumor formation. While cell growth and autophagy are inversely regulated in most cells, elevated levels of autophagy are observed in many established tumors, presumably mediating survival of cancer cells. Still, the relationship of autophagy and oncogenic signaling is poorly characterized. Here we show that the evolutionarily conserved transcription factor Myc (dm), a proto-oncogene involved in cell growth and proliferation, is also a physiological regulator of autophagy in Drosophila melanogaster. Loss of Myc activity in null mutants or in somatic clones of cells inhibits autophagy. Forced expression of Myc results in cell-autonomous increases in cell growth, autophagy induction, and p62 (Ref2P)-mediated activation of Nrf2 (cnc), a transcription factor promoting antioxidant responses. Mechanistically, Myc overexpression increases unfolded protein response (UPR), which leads to PERK-dependent autophagy induction and may be responsible for p62 accumulation. Genetic or pharmacological inhibition of UPR, autophagy or p62/Nrf2 signaling prevents Myc-induced overgrowth, while these pathways are dispensable for proper growth of control cells. In addition, we show that the autophagy and antioxidant pathways are required in parallel for excess cell growth driven by Myc. Deregulated expression of Myc drives tumor progression in most human cancers, and UPR and autophagy have been implicated in the survival of Myc-dependent cancer cells. Our data obtained in a complete animal show that UPR, autophagy and p62/Nrf2 signaling are required for Myc-dependent cell growth. These novel results give additional support for finding future approaches to specifically inhibit the growth of cancer cells addicted to oncogenic Myc.

The evolutionarily conserved transcription factor Myc promotes protein synthesis, cell growth and cancer progression through incompletely understood mechanisms. In this work, we show that forced expression of Myc induces the accumulation of abnormal proteins leading to unfolded protein responses (UPR), presumably by overloading the protein synthetic capacity of cells in Drosophila. UPR then results in autophagy-mediated breakdown and recycling of cytoplasmic material, and at the same time, to activation of antioxidant responses in these cells. Blocking the UPR stress signaling, autophagy and antioxidant pathways genetically, or by feeding larvae an autophagy-inhibiting drug, prevents overgrowth of Myc-expressing cells, but these treatments do not affect the growth of control cells in the same tissues. These results, together with recent reports in mammalian cancer models, suggest that drugs targeting UPR, autophagy and antioxidant responses may specifically inhibit cancer cell proliferation driven by oncogenic Myc.

Mechanism study of goldenseal-associated DNA damage

Goldenseal has been used for the treatment of a wide variety of ailments including gastrointestinal disturbances, urinary tract disorders, and inflammation. The five major alkaloid constituents in goldenseal are berberine, palmatine, hydrastine, hydrastinine, and canadine. When goldenseal was evaluated by the National Toxicology Program (NTP) in the standard 2-year bioassay, goldenseal induced an increase in liver tumors in rats and mice; however, the mechanism of goldenseal-associated liver carcinogenicity remains unknown. In this study, the toxicity of the five goldenseal alkaloid constituents was characterized, and their toxic potencies were compared. As measured by the Comet assay and the expression of γ-H2A.X, berberine, followed by palmatine, appeared to be the most potent DNA damage inducer in human hepatoma HepG2 cells. Berberine and palmatine suppressed the activities of both topoisomerase (Topo) I and II. In berberine-treated cells, DNA damage was shown to be directly associated with the inhibitory effect of Topo II, but not Topo I by silencing gene of Topo I or Topo II. In addition, DNA damage was also observed when cells were treated with commercially available goldenseal extracts and the extent of DNA damage was positively correlated to the berberine content. Our findings suggest that the Topo II inhibitory effect may contribute to berberine- and goldenseal-induced genotoxicity and tumorigenicity.

Dysregulation of the basal RNA polymerase transcription apparatus in cancer

Mutations that directly affect transcription by RNA polymerases rank among the most central mediators of malignant transformation, but the frequency of new anticancer drugs that selectively target defective transcription apparatus entering the clinic has been limited. This is because targeting the large protein-protein and protein-DNA interfaces that control both generic and selective aspects of RNA polymerase transcription has proved extremely difficult. However, recent technological advances have led to a 'quantum leap' in our comprehension of the structure and function of the core RNA polymerase components, how they are dysregulated in a broad range of cancers and how they may be targeted for 'transcription therapy'.

Radiotherapy-induced malignancies: review of clinical features, pathobiology, and evolving approaches for mitigating risk

One of the most significant effects of radiation therapy on normal tissues is mutagenesis, which is the basis for radiation-induced malignancies. Radiation-induced malignancies are late complications arising after radiotherapy, increasing in frequency among survivors of both pediatric and adult cancers. Genetic backgrounds harboring germline mutations in tumor suppressor genes are recognized risk factors. Some success has been found with using genome wide association studies to identify germline polymorphisms associated with susceptibility. The insights generated by genetics, epidemiology, and the development of experimental models are defining potential strategies to offer to individuals at risk for radiation-induced malignancies. Concurrent technological efforts are developing novel radiotherapy delivery to reduce irradiation of normal tissues, and thereby, to mitigate the risk of radiation-induced malignancies. The goal of this review is to discuss epidemiologic, modeling, and radiotherapy delivery data, where these lines of research intersect and their potential impact on patient care.

Cytogenetic abnormalities and monosomal karyotypes in children and adolescents with acute myeloid leukemia: correlations with clinical characteristics and outcome

The whole spectrum of chromosomal abnormalities and their prognostic significance in children and adolescents with acute myeloid leukemia (AML) has not been fully elucidated yet, although a considerable amount of knowledge has been gained recently. Moreover, the incidence and prognostic impact of monosomal karyotypes (MKs), which are new cytogenetic categories reported recently in adults with AML, are currently unknown for childhood and adolescent AML. In this study, we investigated the cytogenetic and clinical characteristics of 140 children and adolescents (≤21 y) with AML, and correlated their cytogenetic features with both the clinical characteristics and outcomes of our patient cohort. The most frequent cytogenetic abnormality found in our study was the t(15;17), followed by the t(8;21). Striking differences in the genetic abnormalities and French-American-British subtypes were found among infants, children, and adolescents. Of 124 cases, 15 (12.1%) met the criteria of the MK definition, and 12 of the 15 MKs (80%) were complex karyotypes. Of 124 cases, 27 (21.8%) had cytogenetic abnormalities sufficient to be diagnosed as AML with myelodyspastic sydrome-related features. As expected, patients with the t(15;17) had the most favorable outcomes, whereas patients with 11q23 rearrangements and monosomy 7 had the worst outcomes. These data expand our knowledge by providing novel insights into the cytogenetic features and their correlations with clinical characteristics and outcomes in childhood and adolescent AML.

Synthesis and characterization of DNA minor groove binding alkylating agents

Derivatives of methyl 3-(1-methyl-5-(1-methyl-5-(propylcarbamoyl)-1H-pyrrol-3-ylcarbamoyl)-1H-pyrrol-3-ylamino)-3-oxopropane-1-sulfonate (1), a peptide-based DNA minor groove binding methylating agent, were synthesized and characterized. In all cases, the N-terminus was appended with an O-methyl sulfonate ester, while the C-terminus group was varied with nonpolar and polar side chains. In addition, the number of pyrrole rings was varied from 2 (dipeptide) to 3 (tripeptide). The ability of the different analogues to efficiently generate N3-methyladenine was demonstrated as was their selectivity for minor groove (N3-methyladenine) versus major groove (N7-methylguanine) methylation. Induced circular dichroism studies were used to measure the DNA equilibrium binding properties of the stable sulfone analogues; the tripeptide binds with affinity that is >10-fold higher than that of the dipeptide. The toxicities of the compounds were evaluated in alkA/tag glycosylase mutant E. coli and in human WT glioma cells and in cells overexpressing and under-expressing N-methylpurine-DNA glycosylase, which excises N3-methyladenine from DNA. The results show that equilibrium binding correlates with the levels of N3-methyladenine produced and cellular toxicity. The toxicity of 1 was inversely related to the expression of MPG in both the bacterial and mammalian cell lines. The enhanced toxicity parallels the reduced activation of PARP and the diminished rate of formation of aldehyde reactive sites observed in the MPG knockdown cells. It is proposed that unrepaired N3-methyladenine is toxic due to its ability to directly block DNA polymerization.

Relapsed or refractory pediatric acute lymphoblastic leukemia: current and emerging treatments

Relapsed acute lymphoblastic leukemia (ALL) represents a major cause of morbidity and mortality in pediatrics. With contemporary chemotherapy, >85% of patients with newly diagnosed ALL survive. Unfortunately, 20% of these patients will relapse and for these children, outcomes remain poor despite our best known chemotherapy protocols. Most of these children will achieve a second complete remission, but maintaining this remission remains difficult. Because relapsed ALL is such a significant cause of morbidity and mortality, it is the focus of much research interest. Efforts have been made and continue to focus on understanding the underlying biology that drives relapse. The role of hematopoietic stem cell transplantation in relapsed ALL remains unclear, but many clinicians still favor this for high-risk patients given the poor prognosis with current chemotherapy alone. It is important to use new drugs with little cross-resistance in the treatment of relapsed ALL. New classes of agents are currently being studied. We also discuss prognostic factors and the biology of relapsed ALL.

Small-molecule inhibitors of DNA damage-repair pathways: an approach to overcome tumor resistance to alkylating anticancer drugs

A major challenge in the future development of cancer therapeutics is the identification of biological targets and pathways, and the subsequent design of molecules to combat the drug-resistant cells hiding in virtually all cancers. This therapeutic approach is justified based upon the limited advances in cancer cures over the past 30 years, despite the development of many novel chemotherapies and earlier detection, which often fail due to drug resistance. Among the various targets to overcome tumor resistance are the DNA repair systems that can reverse the cytotoxicity of many clinically used DNA-damaging agents. Some progress has already been made but much remains to be done. We explore some components of the DNA-repair process, which are involved in repair of alkylation damage of DNA, as targets for the development of novel and effective molecules designed to improve the efficacy of existing anticancer drugs.