PPM1D Mosaic Truncating Variants in Ovarian Cancer Cases May Be Treatment-Related Somatic Mutations

Genetics and epidemiology of mutational barcode-defined clonal hematopoiesis

Clonal hematopoiesis (CH) arises when a substantial proportion of mature blood cells is derived from a single hematopoietic stem cell lineage. Using whole-genome sequencing of 45,510 Icelandic and 130,709 UK Biobank participants combined with a mutational barcode method, we identified 16,306 people with CH. Prevalence approaches 50% in elderly participants. Smoking demonstrates a dosage-dependent impact on risk of CH. CH associates with several smoking-related diseases. Contrary to published claims, we find no evidence that CH is associated with cardiovascular disease. We provide evidence that CH is driven by genes that are commonly mutated in myeloid neoplasia and implicate several new driver genes. The presence and nature of a driver mutation alters the risk profile for hematological disorders. Nevertheless, most CH cases have no known driver mutations. A CH genome-wide association study identified 25 loci, including 19 not implicated previously in CH. Splicing, protein and expression quantitative trait loci were identified for CD164 and TCL1A.

CHIP Happens: Clonal Hematopoiesis of Indeterminate Potential and Its Relationship to Solid Tumors

Clonal hematopoiesis of indeterminate potential (CHIP) is characterized by the expansion of hematopoietic cells harboring leukemia-associated somatic mutations in otherwise healthy people and occurs in at least 10% of adults over 70. It is well established that people with CHIP have increased rates of hematologic malignancy, increased risk of cardiovascular disease, and worse all-cause mortality compared with those without CHIP. Despite recent advancements in understanding CHIP as it relates to these known outcomes, much remains to be learned about the development and role of CHIP in other disease states. Emerging research has identified high rates of CHIP in patients with solid tumors, driven in part by oncologic therapy, and revealed associations between CHIP and differential outcomes in both solid tumors and other diseases. Recent studies have demonstrated that CHIP can contribute to dysregulated inflammatory signaling in multiple contexts, underscoring the importance of interrogating how CHIP might alter tumor immunology. Here, we review the role of CHIP mutations in clonal expansion of hematopoietic cells, explore the relationship between CHIP and solid tumors, and discuss the potential roles of CHIP in inflammation and solid tumor biology.

Clonal hematopoiesis detection in patients with cancer using cell-free DNA sequencing

In the context of cancer, clonal hematopoiesis of indeterminate potential (CHIP) is associated with the development of therapy-related myeloid neoplasms and shorter overall survival. Cell-free DNA (cfDNA) sequencing is becoming widely adopted for genomic screening of patients with cancer but has not been used extensively to determine CHIP status because of a requirement for matched blood and tumor sequencing. We present an accurate classification approach to determine the CH status from cfDNA sequencing alone, applying our model to 4324 oncology clinical cfDNA samples. Using this method, we determined that 30.3% of patients in this cohort have evidence of CH, and the incidence of CH varies by tumor type. Matched RNA sequencing data show evidence of increased inflammation, especially neutrophil activation, within the tumors and tumor microenvironments of patients with CH. In addition, patients with CH had evidence of neutrophil activation systemically, pointing to a potential mechanism of action for the worse outcomes associated with CH status. Neutrophil activation may be one of many mechanisms, however, because patients with estrogen receptor-positive breast cancer harboring TET2 frameshift mutations had worse outcomes but similar neutrophil frequencies to patients without CH. Together, these data show the feasibility of detecting CH through cfDNA sequencing alone and an application of this method, demonstrating increased inflammation in patients with CH both systemically and in the tumor microenvironment.

Analysis of clinical and genomic profiles of therapy-related myeloid neoplasm in Korea

BACKGROUND

Therapy-related myeloid neoplasm (T-MN) rarely occurs among cancer survivors, and was characterized by poor prognosis. T-MN has germline predisposition in a considerable proportion. Here, clinical characteristics and germline/somatic variant profiles in T-MN patients were investigated, and the findings were compared with those of previous studies.

METHODS

A review of medical records, cytogenetic study, targeted sequencing by next-generation sequencing, and survival analysis were performed on 53 patients with T-MN at a single institution in Korea.

RESULTS

The patients were relatively younger compared to T-MN patients in other studies. Our T-MN patients showed a high frequency of complex karyotypes, -5/del(5q), and -7/del(7q), which was similar to the Japanese study group but higher than the Australian study group. The most common primary disease was non-Hodgkin lymphoma, followed by breast cancer. The detailed distributions of primary diseases were different across study groups. Seven patients (13.2%) harbored deleterious presumed/potential germline variants in cancer predisposition genes (CPG) such as BRIP1, CEBPA, DDX41, FANCM, NBN, NF1, and RUNX1. In the somatic variant profile, TP53 was the most frequently mutated gene, which was consistent with the previous studies about T-MN. However, the somatic variant frequency in our study group was lower than in other studies. Adverse factors for overall survival were male sex, older age, history of previous radiotherapy, previous longer cytotoxic therapy, and -5/del(5q).

CONCLUSION

The findings of our study corroborate important information about T-MN patients. As well as a considerable predisposition to CPG, the clinical characteristics and somatic variant profile showed distinctive patterns. Germline variant testing should be recommended for T-MN patients. If the T-MN patients harbor pathogenic germline variants, the family members for stem cell donation should be screened for carrier status through germline variant testing to avoid donor-derived myeloid neoplasm. For the prediction of the prognosis in T-MN patients, sex, age, past treatment history, and cytogenetic findings can be considered.

Clonal hematopoiesis, somatic mosaicism, and age-associated disease

Somatic mosaicism, the occurrence of multiple genetically distinct cell clones within the same tissue, is an evitable consequence of human aging. The hematopoietic system is no exception to this, where studies have revealed the presence of expanded blood cell clones carrying mutations in preleukemic driver genes and/or genetic alterations in chromosomes. This phenomenon is referred to as clonal hematopoiesis and is remarkably prevalent in elderly individuals. While clonal hematopoiesis represents an early step toward a hematological malignancy, most individuals will never develop blood cancer. Somewhat unexpectedly, epidemiological studies have found that clonal hematopoiesis is associated with an increase in the risk of all-cause mortality and age-related disease, particularly in the cardiovascular system. Studies using murine models of clonal hematopoiesis have begun to shed light on this relationship, suggesting that driver mutations in mature blood cells can causally contribute to aging and disease by augmenting inflammatory processes. Here we provide an up-to-date review of clonal hematopoiesis within the context of somatic mosaicism and aging and describe recent epidemiological studies that have reported associations with age-related disease. We will also discuss the experimental studies that have provided important mechanistic insight into how driver mutations promote age-related disease and how this knowledge could be leveraged to treat individuals with clonal hematopoiesis.

Clinical Impact of Next-Generation Sequencing Multi-Gene Panel Highlighting the Landscape of Germline Alterations in Ovarian Cancer Patients

BRCA1 and BRCA2 are the most frequently mutated genes in ovarian cancer (OC) crucial both for the identification of cancer predisposition and therapeutic choices. However, germline variants in other genes could be involved in OC susceptibility. We characterized OC patients to detect mutations in genes other than BRCA1/2 that could be associated with a high risk of developing OC and permit patients to enter the most appropriate treatment and surveillance program. Next-generation sequencing analysis with a 94-gene panel was performed on germline DNA of 219 OC patients. We identified 34 pathogenic/likely pathogenic variants in BRCA1/2 and 38 in other 21 genes. The patients with pathogenic/likely pathogenic variants in the non-BRCA1/2 genes mainly developed OC alone compared to the other groups that also developed breast cancer or other tumors (p = 0.001). Clinical correlation analysis showed that the low-risk patients were significantly associated with platinum sensitivity (p < 0.001). Regarding PARP inhibitors (PARPi) response, the patients with pathogenic mutations in the non-BRCA1/2 genes had worse PFS and OS. Moreover, a statistically significantly worse PFS was found for every increase of one thousand platelets before PARPi treatment. To conclude, knowledge about molecular alterations in genes beyond BRCA1/2 in OC could allow for more personalized diagnostic, predictive, prognostic, and therapeutic strategies for OC patients.

Diagnosis and management of AML in adults: 2022 recommendations from an international expert panel on behalf of the ELN

The 2010 and 2017 editions of the European LeukemiaNet (ELN) recommendations for diagnosis and management of acute myeloid leukemia (AML) in adults are widely recognized among physicians and investigators. There have been major advances in our understanding of AML, including new knowledge about the molecular pathogenesis of AML, leading to an update of the disease classification, technological progress in genomic diagnostics and assessment of measurable residual disease, and the successful development of new therapeutic agents, such as FLT3, IDH1, IDH2, and BCL2 inhibitors. These advances have prompted this update that includes a revised ELN genetic risk classification, revised response criteria, and treatment recommendations.

PPM1D in Solid and Hematologic Malignancies: Friend and Foe?

In the face of constant genomic insults, the DNA damage response (DDR) is initiated to preserve genome integrity; its disruption is a classic hallmark of cancer. Protein phosphatase Mg2+/Mn2+-dependent 1D (PPM1D) is a central negative regulator of the DDR that is mutated or amplified in many solid cancers. PPM1D overexpression is associated with increased proliferative and metastatic behavior in multiple solid tumor types and patients with PPM1D-mutated malignancies have poorer prognoses. Recent findings have sparked an interest in the role of PPM1D in hematologic malignancies. Acquired somatic mutations may provide hematopoietic stem cells with a competitive advantage, leading to a substantial proportion of mutant progeny in the peripheral blood, an age-associated phenomenon termed "clonal hematopoiesis" (CH). Recent large-scale genomic studies have identified PPM1D to be among the most frequently mutated genes found in individuals with CH. While PPM1D mutations are particularly enriched in patients with therapy-related myeloid neoplasms, their role in driving leukemic transformation remains uncertain. Here, we examine the mechanisms through which PPM1D overexpression or mutation may drive malignancy by suppression of DNA repair, cell-cycle arrest, and apoptosis. We also discuss the divergent roles of PPM1D in the oncogenesis of solid versus hematologic cancers with a view to clinical implications and new therapeutic avenues.

Clonal Hematopoiesis: Role in Hematologic and Non-Hematologic Malignancies

Hematopoietic stem cells (HSCs) ensure the coordinated and balanced production of all hematopoietic cell types throughout life. Aging is associated with a gradual decline of the self-renewal and regenerative potential of HSCs and with the development of clonal hematopoiesis. Clonal hematopoiesis of indeterminate potential (CHIP) defines the clonal expansion of genetically variant hematopoietic cells bearing one or more gene mutations and/or structural variants (such as copy number alterations). CHIP increases exponentially with age and is associated with cancers, including hematologic neoplasia, cardiovascular and other diseases. The presence of CHIP consistently increases the risk of hematologic malignancy, particularly in individuals who have CHIP in association with peripheral blood cytopenia.

Inhibition of the DNA damage response phosphatase PPM1D reprograms neutrophils to enhance anti-tumor immune responses

PPM1D/Wip1 is a negative regulator of the tumor suppressor p53 and is overexpressed in several human solid tumors. Recent reports associate gain-of-function mutations of PPM1D in immune cells with worse outcomes for several human cancers. Here we show that mice with genetic knockout of Ppm1d or with conditional knockout of Ppm1d in the hematopoietic system, in myeloid cells, or in neutrophils all display significantly reduced growth of syngeneic melanoma or lung carcinoma tumors. Ppm1d knockout neutrophils infiltrate tumors extensively. Chemical inhibition of Wip1 in human or mouse neutrophils increases anti-tumor phenotypes, p53-dependent expression of co-stimulatory ligands, and proliferation of co-cultured cytotoxic T cells. These results suggest that inhibition of Wip1 in neutrophils enhances immune anti-tumor responses.

Mutations in BRCA1/2 and Other Panel Genes in Patients With Metastatic Breast Cancer -Association With Patient and Disease Characteristics and Effect on Prognosis

PURPOSE

Among patients with metastatic breast cancer (mBC), the frequency of germline mutations in cancer susceptibility genes and the clinical relevance of these mutations are unclear. In this study, a prospective cohort of patients with mBC was used to determine mutation rates for breast cancer (BC) predisposition genes, to evaluate the clinical characteristics of patients with mutations, and to assess the influence of mutations on patient outcome.

PATIENTS AND METHODS

Germline DNA from 2,595 patients with mBC enrolled in the prospective PRAEGNANT registry was evaluated for mutations in cancer predisposition genes. The frequencies of mutations in known BC predisposition genes were compared with results from a prospective registry of patients with nonmetastatic BC sequenced using the same QIAseq method and with public reference controls. Associations between mutation status and tumor characteristics, progression-free survival, and overall survival were assessed.

RESULTS

Germline mutations in 12 established BC predisposition genes (including BRCA1 and BRCA2) were detected in 271 (10.4%) patients. A mutation in BRCA1 or BRCA2 was seen in 129 patients (5.0%). BRCA1 mutation carriers had a higher proportion of brain metastasis (27.1%) compared with nonmutation carriers (12.8%). Mutations were significantly enriched in PRAEGNANT patients with mBC compared with patients with nonmetastatic BC (10.4% v 6.6%, P < .01). Mutations did not significantly modify progression-free survival or overall survival for patients with mBC.

CONCLUSION

Multigene panel testing may be considered in all patients with mBC because of the high frequency of germline mutations in BRCA1/2 and other BC predisposition genes. Although the prognosis of mutation carriers and nonmutation carriers with mBC was similar, differences observed in tumor characteristics have implications for treatment and for future studies of targeted therapies.

Unique roles of rare variants in the genetics of complex diseases in humans

Genome-wide association studies have identified >10,000 genetic variants associated with various phenotypes and diseases. Although the majority are common variants, rare variants with >0.1% of minor allele frequency have been investigated by imputation and using disease-specific custom SNP arrays. Rare variants sequencing analysis mainly revealed have played unique roles in the genetics of complex diseases in humans due to their distinctive features, in contrast to common variants. Unique roles are hypothesis-free evidence for gene causality, a precise target of functional analysis for understanding disease mechanisms, a new favorable target for drug development, and a genetic marker with high disease risk for personalized medicine. As whole-genome sequencing continues to identify more rare variants, the roles associated with rare variants will also increase. However, a better estimation of the functional impact of rare variants across whole genome is needed to enhance their contribution to improvements in human health.

Protein phosphatase, Mg2+/Mn2+-dependent 1D (PPM1D) mutations in haematological cancer

Until recently, the protein phosphatase, Mg²⁺/Mn²⁺-dependent 1D (PPM1D) gene had not been examined in haematological cancer, but several studies have now explored the functional role of this gene and its aberrations. It is often mutated in the context of clonal haemopoiesis (including in patients with lymphoma, myeloproliferative neoplasms and myelodysplastic syndrome) and mutations have been associated with exposure to cytotoxic and radiation therapy, development of therapy-related neoplasms and inferior survival. The vast majority of PPM1D mutations found in haematopoietic cells are of the nonsense or frameshift type and located within terminal exon 6. These genetic defects are rarely found in the blood of healthy individuals. PPM1D encodes the PPM1D phosphatase [also named wild-type p53-induced phosphatase 1 (WIP1)], which negatively regulates signalling molecules within the DNA damage response pathway, including tumour suppressor p53. Clonal expansion of PPM1D mutant haematopoietic cells can potentially be prevented with inhibitors; however, human trials are awaited. In the present review, we provide a review of the literature regarding PPM1D and its role in haematological cancer.

Chasing ctDNA in Patients With Sarcoma

Liquid biopsies are new technologies that allow cancer profiling of tumor fragments found in body fluids, such as peripheral blood, collected noninvasively from patients with malignancies. These assays are increasingly valuable in clinical oncology practice as prognostic biomarkers, as guides for therapy selection, for treatment monitoring, and for early detection of disease progression and relapse. However, application of these assays to rare cancers, such as pediatric and adult sarcomas, have lagged. In this article, we review the technical challenges of applying liquid biopsy technologies to sarcomas, provide an update on progress in the field, describe common pitfalls in interpreting liquid biopsy data, and discuss the intersection of sarcoma clinical care and commercial assays emerging on the horizon.

Genomic heterogeneity in myeloproliferative neoplasms and applications to clinical practice

The myeloproliferative neoplasms (MPN) polycythaemia vera, essential thrombocythaemia and primary myelofibrosis are chronic myeloid disorders associated most often with mutations in JAK2, MPL and CALR, and in some patients with additional acquired genomic lesions. Whilst the molecular mechanisms downstream of these mutations are now clearer, it is apparent that clinical phenotype in MPN is a product of complex interactions, acting between individual mutations, between disease subclones, and between the tumour and background host factors. In this review we first discuss MPN phenotypic driver mutations and the factors that interact with them to influence phenotype. We consider the importance of ongoing studies of clonal haematopoiesis, which may inform a better understanding of why MPN develop in specific individuals. We then consider how best to deploy genomic testing in a clinical environment and the challenges as well as opportunities that may arise from more routine, comprehensive genomic analysis of patients with MPN.

The role of PPM1D in cancer and advances in studies of its inhibitors

A greater understanding of factors causing cancer initiation, progression and evolution is of paramount importance. Among them, the serine/threonine phosphatase PPM1D, also referred to as wild-type p53-induced phosphatase 1 (Wip1) or protein phosphatase 2C delta (PP2Cδ), is emerging as an important oncoprotein due to its negative regulation on a number of crucial cancer suppressor pathways. Initially identified as a p53-regulated gene, PPM1D has been afterwards found amplified and more recently mutated in many human cancers such as breast cancer. The latest progress in this field further reveals that selective inhibition of PPM1D to delay tumor onset or reduce tumor burden represents a promising anti-cancer strategy. Here, we review the advances in the studies of the PPM1D activity and its relevance to various cancers, and recent progress in development of PPM1D inhibitors and discuss their potential application in cancer therapy. Consecutive research on PPM1D and its relationship with cancer is essential, as it ultimately contributes to the etiology and treatment of cancer.

Multigene Panel Germline Testing of 1333 Czech Patients with Ovarian Cancer

Ovarian cancer (OC) is the deadliest gynecologic malignancy with a substantial proportion of hereditary cases and a frequent association with breast cancer (BC). Genetic testing facilitates treatment and preventive strategies reducing OC mortality in mutation carriers. However, the prevalence of germline mutations varies among populations and many rarely mutated OC predisposition genes remain to be identified. We aimed to analyze 219 genes in 1333 Czech OC patients and 2278 population-matched controls using next-generation sequencing. We revealed germline mutations in 18 OC/BC predisposition genes in 32.0% of patients and in 2.5% of controls. Mutations in BRCA1/BRCA2, RAD51C/RAD51D, BARD1, and mismatch repair genes conferred high OC risk (OR > 5). Mutations in BRIP1 and NBN were associated with moderate risk (both OR = 3.5). BRCA1/2 mutations dominated in almost all clinicopathological subgroups including sporadic borderline tumors of ovary (BTO). Analysis of remaining 201 genes revealed somatic mosaics in PPM1D and germline mutations in SHPRH and NAT1 associating with a high/moderate OC risk significantly; however, further studies are warranted to delineate their contribution to OC development in other populations. Our findings demonstrate the high proportion of patients with hereditary OC in Slavic population justifying genetic testing in all patients with OC, including BTO.

Mosaicism, aging and cancer

PURPOSE OF REVIEW

Genetic mosaicism is the presence of a somatic mutation in a subset of cells that differs from the inherited germline genome. Detectable genetic mosaicism is attractive as a potential early biomarker for cancer risk because of its established relationship with aging, introduction of potentially deleterious mutations, and clonal selection and expansion of mutated cells. The aim of this review is to survey shared risk factors associated with genetic mosaicism, aging and cancer risk.

RECENT FINDINGS

Studies have associated aging, cigarette smoking and several genetic susceptibility loci with increased risk of acquiring genetic mosaicism. Genetic mosaicism has also been associated with numerous outcomes including cancer risk and cancer mortality; however, the level of evidence supporting these associations varies considerably.

SUMMARY

Ample evidence exists for shared risk factors for genetic mosaicism and cancer risk as well as abundant support linking genetic mosaicism in leukocytes to hematologic malignancies. The relationship between genetic mosaicism in circulating leukocytes and solid malignancies remains an active area of research.

Clonal hematopoiesis in cancer

Clonal hematopoiesis is a common premalignant condition defined by the abnormal expansion of clonally derived hematopoietic stem cells carrying somatic mutations in leukemia-associated genes. Apart from increasing age, this phenomenon occurs with higher frequency in individuals with lymphoid or solid tumors and is associated with exposures to genotoxic stress. Clonal hematopoiesis in this context confers a greater risk for developing therapy-related myeloid neoplasms and appears to contribute to adverse cancer-related survival through a variety of potential mechanisms. These include alterations of the bone marrow microenvironment, inflammatory changes in clonal effector cells and modulation of immune responses. Understanding how clonal hematopoiesis drives therapy-related myeloid neoplasm initiation and interactions with non-myeloid malignancies will inform screening and surveillance approaches and suggest targeted therapies in this vulnerable population. Here, we examine the clinical implications of clonal hematopoiesis in the cancer setting and discuss potential strategies to mitigate the adverse consequences of clonal expansion.

Somatic mosaic truncating mutations of PPM1D in blood can result from expansion of a mutant clone under selective pressure of chemotherapy

Background

PPM1D (Protein phosphatase magnesium-dependent 1δ) is known as a damage response regulator, a part of the p53 negative feedback loop. Truncating mutations of PPM1D, resulting in overexpression, are frequently found in the blood of patients with breast or ovarian cancer. To identify whether the PPM1D mutation predisposes patients to such cancers or if it results from the cancer and therapy, somatic PPM1D mutations in association with previous cancer and chemotherapy need to be explored.

Methods

We performed next-generation sequencing (NGS) analysis of blood samples from patients suspected to have hereditary cancer. We grouped the patients according to their diagnoses and history of chemotherapy. For the patients with PPM1D mutations in blood, tumor tissue specimens were examined for the PPM1D mutation using conventional sequencing.

Results

A total of 1,195 patients, including 719 patients with breast cancer and 240 with ovarian cancer, were tested, and four (~0.3%) had the truncating mutation in PPM1D. All truncating mutations were in exon 6, in mosaic form, with a mean allele fraction of 11.15%. While 395 out of the 1,195 patients had undergone chemotherapy, the four with the truncating mutation had a history of cisplatin-based chemotherapy. No corresponding mutations were identified in the tumor tissues.

Conclusions

We investigated the frequency of the somatic mosaic PPM1D mutation, in patients with breast or ovarian cancer, which is suggested to be low and related to a history of cisplatin-based chemotherapy. It may be a marker of previous exposure to selective pressure for cells with an impaired DNA damage response.

Detectible mosaic truncating PPM1D mutations, age and breast cancer risk

Mosaic protein truncating variants (PTVs) in the phosphatase, Mg2+/Mn2+dependent 1D (PPM1D) gene in blood-derived DNA have been associated with increased risk of breast cancer. We analyzed PPM1D PTVs in blood from 3817 breast cancer cases and 3058 controls by deep sequencing of a previously defined region in exon 6 of PPM1D. We identified 50 of 6875 (0.73%) participants having a mosaic PPM1D PTV. We observed a higher frequency of mosaic PPM1D PTVs with increasing age (Ptrend = 2.9 × 10-6). We did not observe an overall association between PPM1D PTVs and increased breast cancer risk (OR = 1.51, 95% CI = 0.84-2.71). Evidence for an association was observed in a subset of cases with DNA collected 1-year or more before breast cancer diagnosis (OR = 3.44, 95% CI = 1.62-7.30, P-value = 0.001); however, no significant association was observed for the larger series of cases with DNA collected post diagnosis (OR = 1.01, 95% CI = 0.51-2.01, P-value = 0.98). Our study indicates that the PPM1D PTVs are present at higher rates than previously reported and the frequency of PPM1D PTVs increases with age. We observed limited evidence for an association between mosaic PPM1D PTVs and breast cancer risk, suggesting mosaic PPM1D PTVs in the blood likely do not influence risk of breast cancer.

PPM1D Mutations Drive Clonal Hematopoiesis in Response to Cytotoxic Chemotherapy

Clonal hematopoiesis (CH), in which stem cell clones dominate blood production, becomes increasingly common with age and can presage malignancy development. The conditions that promote ascendancy of particular clones are unclear. We found that mutations in PPM1D (protein phosphatase Mn2+/Mg2+-dependent 1D), a DNA damage response regulator that is frequently mutated in CH, were present in one-fifth of patients with therapy-related acute myeloid leukemia or myelodysplastic syndrome and strongly correlated with cisplatin exposure. Cell lines with hyperactive PPM1D mutations expand to outcompete normal cells after exposure to cytotoxic DNA damaging agents including cisplatin, and this effect was predominantly mediated by increased resistance to apoptosis. Moreover, heterozygous mutant Ppm1d hematopoietic cells outcompeted their wild-type counterparts in vivo after exposure to cisplatin and doxorubicin, but not during recovery from bone marrow transplantation. These findings establish the clinical relevance of PPM1D mutations in CH and the importance of studying mutation-treatment interactions. VIDEO ABSTRACT.

Multigene panel testing beyond BRCA1/2 in breast/ovarian cancer Spanish families and clinical actionability of findings

PURPOSE

Few and small studies have been reported about multigene testing usage by massively parallel sequencing in European cancer families. There is an open debate about what genes should be tested, and the actionability of some included genes is under research.

METHODS

We investigated a panel of 34 known high/moderate-risk cancer genes, including 16 related to breast or ovarian cancer (BC/OC) genes, and 63 candidate genes to BC/OC in 192 clinically suspicious of hereditary breast/ovarian cancer (HBOC) Spanish families without pathogenic variants in BRCA1 or BRCA2 (BRCA1/2).

RESULTS

We identified 16 patients who carried a high- or moderate-risk pathogenic variant in eight genes: 4 PALB2, 3 ATM, 2 RAD51D, 2 TP53, 2 APC, 1 BRIP1, 1 PTEN and 1 PMS2. These findings led to increased surveillance or prevention options in 12 patients and predictive testing in their family members. We detected 383 unique variants of uncertain significance in known cancer genes, of which 35 were prioritized in silico. Eighteen loss-of-function variants were detected in candidate BC/OC genes in 17 patients (1 BARD1, 1 ERCC3, 1 ERCC5, 2 FANCE, 1 FANCI, 2 FANCL, 1 FANCM, 1 MCPH1, 1 PPM1D, 2 RBBP8, 3 RECQL4 and 1 with SLX4 and XRCC2), three of which also carry pathogenic variants in known cancer genes.

CONCLUSIONS

Eight percent of the BRCA1/2 negative patients carry pathogenic variants in other actionable genes. The multigene panel usage improves the diagnostic yield in HBOC testing and it is an effective tool to identify potentially new candidate genes.

PPM1D-truncating mutations confer resistance to chemotherapy and sensitivity to PPM1D inhibition in hematopoietic cells

Truncating mutations in the terminal exon of protein phosphatase Mg2+/Mn2+ 1D (PPM1D) have been identified in clonal hematopoiesis and myeloid neoplasms, with a striking enrichment in patients previously exposed to chemotherapy. In this study, we demonstrate that truncating PPM1D mutations confer a chemoresistance phenotype, resulting in the selective expansion of PPM1D-mutant hematopoietic cells in the presence of chemotherapy in vitro and in vivo. Clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein-9 nuclease mutational profiling of PPM1D in the presence of chemotherapy selected for the same exon 6 mutations identified in patient samples. These exon 6 mutations encode for a truncated protein that displays elevated expression and activity due to loss of a C-terminal degradation domain. Global phosphoproteomic profiling revealed altered phosphorylation of target proteins in the presence of the mutation, highlighting multiple pathways including the DNA damage response (DDR). In the presence of chemotherapy, PPM1D-mutant cells have an abrogated DDR resulting in altered cell cycle progression, decreased apoptosis, and reduced mitochondrial priming. We demonstrate that treatment with an allosteric, small molecule inhibitor of PPM1D reverts the phosphoproteomic, DDR, apoptotic, and mitochondrial priming changes observed in PPM1D-mutant cells. Finally, we show that the inhibitor preferentially kills PPM1D-mutant cells, sensitizes the cells to chemotherapy, and reverses the chemoresistance phenotype. These results provide an explanation for the enrichment of truncating PPM1D mutations in the blood of patients exposed to chemotherapy and in therapy-related myeloid neoplasms, and demonstrate that PPM1D can be a targeted in the prevention of clonal expansion of PPM1D-mutant cells and the treatment of PPM1D-mutant disease.

Cancer genetics, precision prevention and a call to action

More than 15 years have passed since the identification, through linkage, of 'first-wave' susceptibility genes for common cancers (BRCA1, BRCA2, MLH1 and MSH2). These genes have strong frequency-penetrance profiles, such that the associated clinical utility probably remains relevant regardless of the context of ascertainment. 'Second-wave' genes, not tractable by linkage, were subsequently identified by mutation screening of candidate genes (PALB2, ATM, CHEK2, BRIP1, RAD51C and RAD51D). Their innately weaker frequency-penetrance profiles have rendered delineation of cancer associations, risks and variant pathogenicity challenging, thereby compromising their clinical application. Early germline exome-sequencing endeavors for common cancers did not yield the long-anticipated slew of 'next-wave' genes but instead implied a highly polygenic genomic architecture requiring much larger experiments to make any substantive inroads into gene discovery. As such, the 'genetic economics' of frequency penetrance clearly indicates that focused identification of carriers of first-wave-gene mutations is most impactful for cancer control. With screening, prevention and early detection at the forefront of the cancer management agenda, we propose that the time is nigh for the initiation of national population-testing programs to identify carriers of first-wave gene mutation carriers. To fully deliver a precision prevention program, long-term, large-scale mutation studies that capture longitudinal clinical data and serial biosamples are required.

Therapy-related myeloid neoplasms: when genetics and environment collide

Therapy-related myeloid neoplasms (t-MN) arise as a late effect of chemotherapy and/or radiation administered for a primary condition, typically a malignant disease, solid organ transplant or autoimmune disease. Survival is measured in months, not years, making t-MN one of the most aggressive and lethal cancers. In this Review, we discuss recent developments that reframe our understanding of the genetic and environmental aetiology of t-MN. Emerging data are illuminating who is at highest risk of developing t-MN, why t-MN are chemoresistant and how we may use this information to treat and ultimately prevent this lethal disease.

Therapy-Related Clonal Hematopoiesis in Patients with Non-hematologic Cancers Is Common and Associated with Adverse Clinical Outcomes

Clonal hematopoiesis (CH), as evidenced by recurrent somatic mutations in leukemia-associated genes, commonly occurs among aging human hematopoietic stem cells. We analyzed deep-coverage, targeted, next-generation sequencing (NGS) data of paired tumor and blood samples from 8,810 individuals to assess the frequency and clinical relevance of CH in patients with non-hematologic malignancies. We identified CH in 25% of cancer patients, with 4.5% harboring presumptive leukemia driver mutations (CH-PD). CH was associated with increased age, prior radiation therapy, and tobacco use. PPM1D and TP53 mutations were associated with prior exposure to chemotherapy. CH and CH-PD led to an increased incidence of subsequent hematologic cancers, and CH-PD was associated with shorter patient survival. These data suggest that CH occurs in an age-dependent manner and that specific perturbations can enhance fitness of clonal hematopoietic stem cells, which can impact outcome through progression to hematologic malignancies and through cell-non-autonomous effects on solid tumor biology.

Mosaic mutations in blood DNA sequence are associated with solid tumor cancers

Recent understanding of the causal role of blood-detectable somatic protein-truncating DNA variants in leukemia prompts questions about the generalizability of such observations across cancer types. We used the cancer genome atlas exome sequencing (~8000 samples) to compare 22 different cancer phenotypes with more than 6000 controls using a case–control study design and demonstrate that mosaic protein truncating variants in these genes are also associated with solid-tumor cancers. The absence of these cancer-associated mosaic variants from the tumors themselves suggest these are not themselves tumor drivers. Through analysis of different cancer phenotypes we observe gene-specificity for mosaic mutations. We confirm a specific link between PPM1D and ovarian cancer, consistent with previous reports linking PPM1D to breast and ovarian cancer. Additionally, glioblastoma, melanoma and lung cancers show gene specific burdens of mosaic protein truncating mutations. Taken together, these results extend existing observations and broadly link solid-tumor cancers to somatic blood DNA changes.

Increased risk for solid tumors linked to mutations detected in blood samples that shorten the coding sequence of their genes. Mark Daly and colleagues from the Broad Institute in Cambridge, Massachusetts, USA, used large genomic databases to test whether having blood cells both with and without genetic variants predicted to shorten the encoded protein—a phenomenon known as mosaic protein-truncating variants (PTVs)—was associated with developing a range of solid-tumor cancers. They studied DNA from around 8,000 people with cancer and 6,000 healthy controls. Other studies have shown that mosaic PTVs precede and predict the development of leukemia. In this study, the scientists not only confirmed previous reports linking these variants to breast and ovarian cancer but also extended the association to include tumors of the brain, skin and lungs. These results broadly connect cancer to blood DNA changes.

Clonal hematopoiesis, with and without candidate driver mutations, is common in the elderly

Clonal hematopoiesis (CH) arises when a substantial proportion of mature blood cells is derived from a single dominant hematopoietic stem cell lineage. Somatic mutations in candidate driver (CD) genes are thought to be responsible for at least some cases of CH. Using whole-genome sequencing of 11 262 Icelanders, we found 1403 cases of CH by using barcodes of mosaic somatic mutations in peripheral blood, whether or not they have a mutation in a CD gene. We find that CH is very common in the elderly, trending toward inevitability. We show that somatic mutations in TET2, DNMT3A, ASXL1, and PPM1D are associated with CH at high significance. However, known CD mutations were evident in only a fraction of CH cases. Nevertheless, the highly prevalent CH we detect associates with increased mortality rates, risk for hematological malignancy, smoking behavior, telomere length, Y-chromosome loss, and other phenotypic characteristics. Modeling suggests some CH cases could arise in the absence of CD mutations as a result of neutral drift acting on a small population of active hematopoietic stem cells. Finally, we find a germline deletion in intron 3 of the telomerase reverse transcriptase (TERT) gene that predisposes to CH (rs34002450; P = 7.4 × 10^-12; odds ratio, 1.37).

Predictors of pretreatment CA125 at ovarian cancer diagnosis: a pooled analysis in the Ovarian Cancer Association Consortium

PURPOSE

Cancer antigen 125 (CA125) is a glycoprotein expressed by epithelial cells of several normal tissue types and overexpressed by several epithelial cancers. Serum CA125 levels are mostly used as an aid in the diagnosis of ovarian cancer patients, to monitor response to treatment and detect cancer recurrence. Besides tumor characteristics, CA125 levels are also influenced by several epidemiologic factors, such as age, parity, and oral contraceptive use. Identifying factors that influence CA125 levels in ovarian cancer patients could aid in the interpretation of CA125 values for individuals.

METHODS

We evaluated predictors of pretreatment CA125 in 13 studies participating in the Ovarian Cancer Association Consortium. This analysis included a total of 5,091 women with invasive epithelial ovarian cancer with pretreatment CA125 measurements. We used probit scores to account for variability in CA125 between studies and linear regression to estimate the association between epidemiologic factors and tumor characteristics and pretreatment CA125 levels.

RESULTS

In age-adjusted models, older age, history of pregnancy, history of tubal ligation, family history of breast cancer, and family history of ovarian cancer were associated with higher CA125 levels while endometriosis was associated with lower CA125 levels. After adjusting for tumor-related characteristics (stage, histology, grade), body mass index (BMI) higher than 30 kg/m2 was associated with 10% (95% CI 2, 19%) higher CA125 levels, while race (non-white vs. white) was associated with 15% (95% CI 4, 27%) higher CA125 levels.

CONCLUSION

Our results suggest that high BMI and race may influence CA125 levels independent of tumor characteristics. Validation is needed in studies that use a single assay for CA125 measurement and have a diverse study population.

De Novo Truncating Mutations in the Last and Penultimate Exons of PPM1D Cause an Intellectual Disability Syndrome

Intellectual disability (ID) is a highly heterogeneous disorder involving at least 600 genes, yet a genetic diagnosis remains elusive in ∼35%-40% of individuals with moderate to severe ID. Recent meta-analyses statistically analyzing de novo mutations in >7,000 individuals with neurodevelopmental disorders highlighted mutations in PPM1D as a possible cause of ID. PPM1D is a type 2C phosphatase that functions as a negative regulator of cellular stress-response pathways by mediating a feedback loop of p38-p53 signaling, thereby contributing to growth inhibition and suppression of stress-induced apoptosis. We identified 14 individuals with mild to severe ID and/or developmental delay and de novo truncating PPM1D mutations. Additionally, deep phenotyping revealed overlapping behavioral problems (ASD, ADHD, and anxiety disorders), hypotonia, broad-based gait, facial dysmorphisms, and periods of fever and vomiting. PPM1D is expressed during fetal brain development and in the adult brain. All mutations were located in the last or penultimate exon, suggesting escape from nonsense-mediated mRNA decay. Both PPM1D expression analysis and cDNA sequencing in EBV LCLs of individuals support the presence of a stable truncated transcript, consistent with this hypothesis. Exposure of cells derived from individuals with PPM1D truncating mutations to ionizing radiation resulted in normal p53 activation, suggesting that p53 signaling is unaffected. However, a cell-growth disadvantage was observed, suggesting a possible effect on the stress-response pathway. Thus, we show that de novo truncating PPM1D mutations in the last and penultimate exons cause syndromic ID, which provides additional insight into the role of cell-cycle checkpoint genes in neurodevelopmental disorders.

Clonal Hematopoiesis Associated With Adverse Outcomes After Autologous Stem-Cell Transplantation for Lymphoma

Purpose Clonal hematopoiesis of indeterminate potential (CHIP) is an age-related condition characterized by somatic mutations in the blood of otherwise healthy adults. We hypothesized that in patients undergoing autologous stem-cell transplantation (ASCT) for lymphoma, CHIP at the time of ASCT would be associated with an increased risk of myelodysplastic syndrome and acute myeloid leukemia, collectively termed therapy-related myeloid neoplasm (TMN), and other adverse outcomes. Methods We performed whole-exome sequencing on pre- and post-ASCT samples from 12 patients who developed TMN after autologous transplantation for Hodgkin lymphoma or non-Hodgkin lymphoma and targeted sequencing on cryopreserved aliquots of autologous stem-cell products from 401 patients who underwent ASCT for non-Hodgkin lymphoma between 2003 and 2010. We assessed the effect of CHIP at the time of ASCT on subsequent outcomes, including TMN, cause-specific mortality, and overall survival. Results For six of 12 patients in the exome sequencing cohort, mutations found in the TMN specimen were also detectable in the pre-ASCT specimen. In the targeted sequencing cohort, 120 patients (29.9%) had CHIP at the time of ASCT, which was associated with an increased rate of TMN (10-year cumulative incidence, 14.1% v 4.3% for those with and without CHIP, respectively; P = .002). Patients with CHIP had significantly inferior overall survival compared with those without CHIP (10-year overall survival, 30.4% v 60.9%, respectively; P < .001), including increased risk of death from TMN and cardiovascular disease. Conclusion In patients undergoing ASCT for lymphoma, CHIP at the time of transplantation is associated with inferior survival and increased risk of TMN.

The ageing genome, clonal mosaicism and chronic disease

Clonal mosaicism arises when a postzygotic mutational event is detectable in subpopulations of cells as an alternative genotype while not present in the germline genome. Although described in a subset of pediatric disorders, new genomic technologies have detected higher than anticipated frequencies of clonal mosaicism in adult population studies, stimulating investigation as to how clonal mosaicism could contribute to chronic human diseases, such as cancer, diabetes and neurodegenerative disorders. It has also been postulated to be an important mechanism for functional cellular diversity, including the brain. Early studies have characterized the spectrum of detectable mosaic alterations and have begun to investigate whether detectable mosaicism could be important as an overall biomarker for risk or in the case of hematologic cancers, identification of preleukemic clones.

Therapy-related myeloid neoplasms: does knowing the origin help to guide treatment?

Therapy-related myeloid neoplasms (t-MN) combine t-MDS and therapy related acute myeloid leukemia (t-AML) patients in one entity because of their similar pathogenesis, rapid progression from t-MDS to t-AML, and their equally poor prognosis. Treatment with epipodophyllotoxins like etoposide has been associated with a short interval between treatment and development of t-AML, with fusion oncogenes like KMT2A/MLL-MLLT3 and a better prognosis. In contrast, treatment with alkylating agents has been associated with a longer latency, an initial MDS phase, adverse cytogenetics, and a poor prognosis. The pathogenesis of t-MN can be explained by direct induction of an oncogene through chromosomal translocations, induction of genetic instability, or selection of a preexisting treatment-resistant hematopoietic stem cell clone. Recent evidence has highlighted the importance of the last mechanism and explains the high frequency of TP53 mutations in patients with t-MN. After previous cytotoxic therapy, patients present with specific vulnerabilities, especially evident from the high nonrelapse mortality in patients with t-MN after allogeneic hematopoietic cell transplantation. Here, the prognostic impact of currently known risk factors and the therapeutic options in different patient subgroups will be discussed.

Therapy-related myeloid neoplasms: does knowing the origin help to guide treatment?

Therapy-related myeloid neoplasms (t-MN) combine t-MDS and therapy related acute myeloid leukemia (t-AML) patients in one entity because of their similar pathogenesis, rapid progression from t-MDS to t-AML, and their equally poor prognosis. Treatment with epipodophyllotoxins like etoposide has been associated with a short interval between treatment and development of t-AML, with fusion oncogenes like KMT2A/MLL-MLLT3 and a better prognosis. In contrast, treatment with alkylating agents has been associated with a longer latency, an initial MDS phase, adverse cytogenetics, and a poor prognosis. The pathogenesis of t-MN can be explained by direct induction of an oncogene through chromosomal translocations, induction of genetic instability, or selection of a preexisting treatment-resistant hematopoietic stem cell clone. Recent evidence has highlighted the importance of the last mechanism and explains the high frequency of TP53 mutations in patients with t-MN. After previous cytotoxic therapy, patients present with specific vulnerabilities, especially evident from the high nonrelapse mortality in patients with t-MN after allogeneic hematopoietic cell transplantation. Here, the prognostic impact of currently known risk factors and the therapeutic options in different patient subgroups will be discussed.

Diagnosis and management of AML in adults: 2017 ELN recommendations from an international expert panel

The first edition of the European LeukemiaNet (ELN) recommendations for diagnosis and management of acute myeloid leukemia (AML) in adults, published in 2010, has found broad acceptance by physicians and investigators caring for patients with AML. Recent advances, for example, in the discovery of the genomic landscape of the disease, in the development of assays for genetic testing and for detecting minimal residual disease (MRD), as well as in the development of novel antileukemic agents, prompted an international panel to provide updated evidence- and expert opinion-based recommendations. The recommendations include a revised version of the ELN genetic categories, a proposal for a response category based on MRD status, and criteria for progressive disease.

Truncating and missense PPM1D mutations in early-onset and/or familial/hereditary prostate cancer patients

Truncating activating mutations in the last exon of PPM1D have been described in patients with breast, ovarian, colorectal and non-small cell lung cancer, but recent data indicate that they may be associated with previous chemotherapy. In this study we evaluated the prevalence of PPM1D mutations in white blood cells (WBC) of 462 patients with early-onset and/or familial/hereditary prostate cancer (PrCa) by sequencing the coding region of exon 6. Two truncating mutations were found in two patients (0.4%), both treated with androgen-ablation therapy but no chemotherapy prior to blood collection. Next generation sequencing analysis showed that the truncating variants were present in 21.4% and 32.4% of the reads, indicating that they were in mosaic in WBC, something that was confirmed by its absence in a different tissue from one of these patients. Additionally, nine patients (1.95%) were found to harbor non-synonymous germline mutations, with three patients sharing the same missense variant, c.1607G > A, p.Arg536Lys. This variant was predicted to be deleterious by different in silico tools and was not found in the 293 male control subjects tested. Large cohorts and/or functional evaluation are needed to clarify the nature of the truncating mosaic mutations in PrCa patients treated with and without androgen-ablation therapy and to evaluate the contribution of the recurrent missense variant to the risk of developing PrCa. © 2016 Wiley Periodicals, Inc.

Rare ATAD5 missense variants in breast and ovarian cancer patients

ATAD5/ELG1 is a protein crucially involved in replication and maintenance of genome stability. ATAD5 has recently been identified as a genomic risk locus for both breast and ovarian cancer through genome-wide association studies. We aimed to investigate the spectrum of coding ATAD5 germ-line mutations in hospital-based series of patients with triple-negative breast cancer or serous ovarian cancer compared with healthy controls. The ATAD5 coding and adjacent splice site regions were analyzed by targeted next-generation sequencing of DNA samples from 273 cancer patients, including 114 patients with triple-negative breast cancer and 159 patients with serous epithelial ovarian cancer, and from 276 healthy females. Among 42 different variants identified, twenty-two were rare missense substitutions, of which 14 were classified as pathogenic by at least one in silico prediction tool. Three of four novel missense substitutions (p.S354I, p.H974R and p.K1466N) were predicted to be pathogenic and were all identified in ovarian cancer patients. Overall, rare missense variants with predicted pathogenicity tended to be enriched in ovarian cancer patients (14/159) versus controls (11/276) (p = 0.05, 2df). While truncating germ-line variants in ATAD5 were not detected, it remains possible that several rare missense variants contribute to genetic susceptibility toward epithelial ovarian carcinomas.