The two-hit theory hits 50

Bayesian analysis of the rate of spontaneous malignant mesothelioma among BAP1 mutant mice in the absence of asbestos exposure

Cancers of the mesothelium, such as malignant mesothelioma (MM), historically have been attributed solely to exposure to asbestos. Recent large scale genetic and genomic functional studies now show that approximately 20% of all human mesotheliomas are causally linked to highly penetrant inherited (germline) pathogenic mutations in numerous cancer related genes. The rarity of these mutations in humans makes it difficult to perform statistically conclusive genetic studies to understand their biological effects. This has created a disconnect between functional and epidemiological studies. However, since the molecular pathogenesis of MM in mice accurately recapitulates that of human disease, this disconnect between functional and epidemiological studies can be overcome by using inbred mouse strains that harbor mutation(s) in genes involved in the disease. Most mouse studies have focused on the effect of asbestos exposure, leaving the effects of genetic mutations in the absence of exposure understudied. Here, using existing peer-reviewed studies, we investigate the rate of spontaneous MM among mice with and without germline genetic mutations, in the absence of asbestos exposure. We leveraged these published data to generate a historical control dataset (HCD) to allow us to improve statistical power and account for genetic heterogeneity between studies. Our Bayesian analyses indicate that the odds of spontaneous MM among germline BAP1 mutant mice is substantially larger than that of wildtype mice. These results support the existing biological study findings that mesotheliomas can arise in the presence of pathogenic germline mutations, independently of asbestos exposure.

Global, regional and national burden due to retinoblastoma in children aged younger than 10 years from 1990 to 2021

BACKGROUND

Retinoblastoma (RB), an aggressive intraocular malignancy, significantly adds to the global disease burden in early childhood. This study offers insights into the global burden of retinoblastoma (RB) in children aged 0-9 years, examining incidence, mortality, and DALYs from 1990 to 2021, across age, sex, location, and SDI levels. It aims to inform health policy, resource allocation, and RB combat strategies.

METHODS

Data were retrieved from newly released Global Burden of Disease (GBD) study. The measures were estimated both as numerical counts and age-standardised rates per 100,000 population. Joinpoint regression analysis was used to rigorously examine temporal trends, estimating the average annual percentage change (AAPC). Spearman's correlation test was used to examine the relationship between SDI and the burden of RB by location and year.

RESULTS

Globally, the age-standardised incidence rate (ASIR), age-standardised mortality rate (ASMR), and age-standardised DALYs rate (ASDR) for RB among young children in 2021 were 0.09 [95% uncertainty interval (UI): 0.05 to 0.13], 0.04 (95%UI: 0.03 to 0.06), and 3.65 (95%UI: 2.21 to 4.96), respectively. Despite an overall increasing trend in incidence [AAPC: 0.62; 95% confidence interval (CI): 0.42 to 0.82], the RB incidence rate demonstrated a significant decline from 2019 to 2021, while mortality and DALYs rate for RB showed overall downward trends. Trends in ASIR varied across regions, with the highest increase in East Asia. Among all GBD regions, only Southern Sub-Saharan Africa exhibited rising trends in mortality and DALYs rate. Gender comparisons showed negligible differences in ASIR, ASMR and ASDR in 2021. Moreover, the highest disease burden was noted in early neonatal (0-6 days), and in children aged 2-4 years at both global and regional levels. Analysis by SDI indicated that RB incidence rates increased with higher SDI levels. In addition, a significantly negative correlation was found between SDI level and both ASMR and ASDR of RB among children aged 0-9 years.

CONCLUSIONS

From 1990 to 2021, RB-related incidence, mortality, and DALYs varied by age and location. Evaluating spatiotemporal trends underscores the impact of health policies and substantial public health interventions on RB control.

Principles of Tumor Biology

Cancer is disease of the genome. The Hallmarks of cancer are a way of thinking of cancer to help rationalize what occurs in this disease process. A solid tumor is a complex of normal and neoplastic cells, arising through an evolutionary process to survive and grow. By understanding how normal cellular mechanisms are subverted to promote cancer we can refine our approach to improve outcomes. It gives us opportunities to prevent some cancers and allowing earlier diagnosis. We can refine conventional diagnostic tools and give more accurate prognoses. It offers novel targets to improve treatment of cancers, allowing personalized medicine.

Mediastinal Teratoma with Nephroblastomatous Elements: Case Report, Literature Review, and Comparison with Maturing Fetal Glomerulogenic Zone/Definitive Zone Ratio and Nephrogenic Rests

Extrarenal teratoid Wilms' tumor (TWT) is a variant of Wilms' tumor with fewer than 30 cases reported in the literature. It comprises more than 50% heterologous tissue and presents a significant diagnostic challenge due to its complex histology. We report an unusual case of mediastinal teratoma with nephroblastomatous elements in an 8-year-old female. The patient presented with respiratory distress, fever, weight loss, and a large anterior mediastinal mass. Imaging revealed a heterogeneous tumor containing fat, fluid, and calcification, suggestive of a teratoma. Surgical resection confirmed a mature cystic teratoma with foci of nephroblastoma. Pathological analysis demonstrated a mixture of ectodermal, mesodermal, and endodermal tissues alongside nephroblastomatous components. Immunohistochemistry was positive for Wilms Tumor 1 and other relevant markers, confirming the diagnosis. The patient had an uneventful postoperative course and was discharged after three days. This case adds to the growing body of research on extrarenal TWT, particularly its occurrence in the mediastinum, a rare site for such tumors. A literature review highlighted that extrarenal TWT often affects children, typically presenting in the retroperitoneum or sacrococcygeal regions, with varying recurrence rates and long-term outcomes. This case underscores the importance of histopathological and immunohistochemical analysis in diagnosing TWT and differentiating it from other mediastinal tumors to ensure appropriate treatment planning, emphasizing the need for long-term follow-up due to the potential for recurrence or metastasis. This paper also provides an in-depth look at nephron development and nephrogenic rests, highlighting the structural and functional aspects of nephrogenesis and the factors that disrupt it in fetal kidneys.

The Prevalence of Cancer Predisposition Syndromes (CPSs) in Children with a Neoplasm: A Cohort Study in a Central and Eastern European Population

IMPORTANCE

The etiology of pediatric cancers is often unclear; however, advancements in genetics have identified significant roles for genetic disorders in their development. Over time, the number of cancer predisposition syndromes (CPSs) and awareness of them have increased, providing the possibility of cancer prevention and early detection.

PURPOSE

In this study, we present data concerning the number and type of oncological cases and their correlation with CPS occurrence in a cohort of Central and Eastern European pediatric patients.

MATERIALS

The data were collected between 2000 and 2019 at the Karol Jonscher Clinical Hospital of Poznan University of Medical Sciences, resulting in a cohort of 2190 cases in total, of which 193 children (8.81%) were confirmed to have a CPS.

RESULTS

CPSs occurred most frequently in infancy (22.90% of all children suffering from any diagnosed cancer during the first year of life; p < 0.0001), accounting for more than one-quarter of all CPS cases in our cohort. CPSs were least likely to be observed in patients aged 14 and 15 years (2.17% and 2.44% of children diagnosed with any of the listed cancers at the exact age, respectively; p < 0.05). Among CPSs, the most common were neurofibromatosis type I (NF1), Li-Fraumeni syndrome (LFS), and Down syndrome (DS).

CONCLUSIONS

To conclude, it is important to emphasize the need for personalized treatment for each patient affected by both CPSs and subsequent cancer in order to reduce the toxicity of therapy and improve quality of life by reducing the risk of side effects.

KRIT1 in vascular biology and beyond

KRIT1 is a 75 kDa scaffolding protein which regulates endothelial cell phenotype by limiting the response to inflammatory stimuli and maintaining a quiescent and stable endothelial barrier. Loss-of-function mutations in KRIT1 lead to the development of cerebral cavernous malformations (CCM), a disease marked by the formation of abnormal blood vessels which exhibit a loss of barrier function, increased endothelial proliferation, and altered gene expression. While many advances have been made in our understanding of how KRIT1, and the functionally related proteins CCM2 and PDCD10, contribute to the regulation of blood vessels and the vascular barrier, some important open questions remain. In addition, KRIT1 is widely expressed and KRIT1 and the other CCM proteins have been shown to play important roles in non-endothelial cell types and tissues, which may or may not be related to their role as pathogenic originators of CCM. In this review, we discuss some of the unsettled questions regarding the role of KRIT1 in vascular physiology and discuss recent advances that suggest this ubiquitously expressed protein may have a role beyond the endothelial cell.

Co-expression in tissue-specific gene networks links genes in cancer-susceptibility loci to known somatic driver genes

BACKGROUND

The genetic background of cancer remains complex and challenging to integrate. Many somatic mutations within genes are known to cause and drive cancer, while genome-wide association studies (GWAS) of cancer have revealed many germline risk factors associated with cancer. However, the overlap between known somatic driver genes and positional candidate genes from GWAS loci is surprisingly small. We hypothesised that genes from multiple independent cancer GWAS loci should show tissue-specific co-regulation patterns that converge on cancer-specific driver genes.

RESULTS

We studied recent well-powered GWAS of breast, prostate, colorectal and skin cancer by estimating co-expression between genes and subsequently prioritising genes that show significant co-expression with genes mapping within susceptibility loci from cancer GWAS. We observed that the prioritised genes were strongly enriched for cancer drivers defined by COSMIC, IntOGen and Dietlein et al. The enrichment of known cancer driver genes was most significant when using co-expression networks derived from non-cancer samples of the relevant tissue of origin.

CONCLUSION

We show how genes within risk loci identified by cancer GWAS can be linked to known cancer driver genes through tissue-specific co-expression networks. This provides an important explanation for why seemingly unrelated sets of genes that harbour either germline risk factors or somatic mutations can eventually cause the same type of disease.

Genetic and biological drivers of prostate cancer disparities in Black men

Black men with prostate cancer have historically had worse outcomes than white men with prostate cancer. The causes of this disparity in outcomes are multi-factorial, but a potential basis is that prostate cancers in Black men are biologically distinct from prostate cancers in white men. Evidence suggests that genetic and ancestral factors, molecular pathways involving androgen and non-androgen receptor signalling, inflammation, epigenetics, the tumour microenvironment and tumour metabolism are contributing factors to the racial disparities observed. Key genetic and molecular pathways linked to prostate cancer risk and aggressiveness have potential clinical relevance. Describing biological drivers of prostate cancer disparities could inform efforts to improve outcomes for Black men with prostate cancer.

The Genetics of Tuberous Sclerosis Complex and Related mTORopathies: Current Understanding and Future Directions

The mechanistic target of rapamycin (mTOR) pathway serves as a master regulator of cell growth, proliferation, and survival. Upregulation of the mTOR pathway has been shown to cause malformations of cortical development, medically refractory epilepsies, and neurodevelopmental disorders, collectively described as mTORopathies. Tuberous sclerosis complex (TSC) serves as the prototypical mTORopathy. Characterized by the development of benign tumors in multiple organs, pathogenic variants in TSC1 or TSC2 disrupt the TSC protein complex, a negative regulator of the mTOR pathway. Variants in critical domains of the TSC complex, especially in the catalytic TSC2 subunit, correlate with increased disease severity. Variants in less crucial exons and non-coding regions, as well as those undetectable with conventional testing, may lead to milder phenotypes. Despite the assumption of complete penetrance, expressivity varies within families, and certain variants delay disease onset with milder neurological effects. Understanding these genotype-phenotype correlations is crucial for effective clinical management. Notably, 15% of patients have no mutation identified by conventional genetic testing, with the majority of cases postulated to be caused by somatic TSC1/TSC2 variants which present complex diagnostic challenges. Advancements in genetic testing, prenatal screening, and precision medicine hold promise for changing the diagnostic and treatment paradigm for TSC and related mTORopathies. Herein, we explore the genetic and molecular mechanisms of TSC and other mTORopathies, emphasizing contemporary genetic methods in understanding and diagnosing the condition.

Uncovering Minimal Pathways in Melanoma Initiation

Cutaneous melanomas are clinically and histologically heterogeneous. Most display activating mutations in Braf or Nras and complete loss of function of one or more tumor suppressor genes. Mouse models that replicate such mutations produce fast-growing, pigmented tumors. However, mice that combine Braf activation with only heterozygous loss of Pten also produce tumors and, as we show here, in an Albino background this occurs even with Braf activation alone. Such tumors arise rarely, grow slowly, and express low levels of pigmentation genes. The timing of their appearance was consistent with a single step stochastic event, but no evidence could be found that it required de novo mutation, suggesting instead the involvement of an epigenetic transition. Single-cell transcriptomic analysis revealed such tumors to be heterogeneous, including a minor cell type we term LNM ( L ow-pigment, N eural- and extracellular M atrix-signature) that displays gene expression resembling "neural crest"-like cell subsets detected in the fast-growing tumors of more heavily-mutated mice, as well as in human biopsy and xenograft samples. We provide evidence that LNM cells pre-exist in normal skin, are expanded by Braf activation, can transition into malignant cells, and persist with malignant cells through multiple rounds of transplantation. We discuss the possibility that LNM cells not only serve as a pre-malignant state in the production of some melanomas, but also as an important intermediate in the development of drug resistance.

Single-nucleus DNA sequencing reveals hidden somatic loss-of-heterozygosity in Cerebral Cavernous Malformations

Cerebral Cavernous Malformations (CCMs) are vascular malformations of the central nervous system which can lead to moderate to severe neurological phenotypes in patients. A majority of CCM lesions are driven by a cancer-like three-hit mutational mechanism, including a somatic, activating mutation in the oncogene PIK3CA, as well as biallelic loss-of-function mutations in a CCM gene. However, standard sequencing approaches often fail to yield a full complement of pathogenic mutations in many CCMs. We suggest this reality reflects the limited sensitivity to identify low-frequency variants and the presence of mutations undetectable with bulk short-read sequencing. Here we report a single-nucleus DNA-sequencing approach that leverages the underlying biology of CCMs to identify lesions with somatic loss-of-heterozygosity, a class of such hidden mutations. We identify an alternative genetic mechanism for CCM pathogenesis and establish a method that can be repurposed to investigate the genetic underpinning of other disorders with multiple somatic mutations.

Aligning germline and somatic mutations in prostate cancer. Are genetics changing practice?

OBJECTIVE

To review the current status of germline and somatic (tumour) genetic testing for prostate cancer (PCa), and its relevance for clinical practice.

METHODS

A narrative synthesis of various molecular profiles related to their clinical context was carried out. Current guidelines for genetic testing and its feasibility in clinical practice were analysed. We report the main identified genetic sequencing results or functional genomic scores for PCa published in the literature or obtained from the French PROGENE study.

RESULTS

The molecular alterations observed in PCa are mostly linked to disruption of the androgen receptor (AR) pathway or DNA repair deficiency. The main known germline mutations affect the BReast CAncer gene 2 (BRCA2) and homeobox B13 (HOXB13) genes, whereas AR and tumour protein p53 (TP53) are the genes with most frequent somatic alterations in tumours from men with metastatic PCa. Molecular tests are now available for detecting some of these germline or somatic alterations and sometimes recommended by guidelines, but their utilisation must combine rationality and feasibility. They can guide specific therapies, notably for the management of metastatic disease. Indeed, following androgen deprivation, targeted therapies for PCa currently include poly-(ADP-ribose)-polymerase (PARP) inhibitors, immune checkpoint inhibitors, and prostate-specific membrane antigen (PSMA)-guided radiotherapy. The genetic tests currently approved for targeted therapies remain limited to the detection of BRCA1 and BRCA2 mutation and DNA mismatch repair deficiency, while large panels are recommended for germline analyses, not only for inherited cancer predisposing syndrome, but also for metastatic PCa.

CONCLUSIONS

Further consensus aligning germline with somatic molecular analysis in metastatic PCa is required, including genomics scars, emergent immunohistochemistry, or functional pre-screen imaging. With rapid advances in knowledge and technology in the field, continuous updating of guidelines to help the clinical management of these individuals, and well-conducted studies to evaluate the benefits of genetic testing are needed.

A Decrease in Effective Renal Perfusion Pressure Is Associated With Increased Acute Kidney Injury in Patients Undergoing Cardiac Surgery

PURPOSE

This study aimed to evaluate the relationship between intra-abdominal pressure (IAP), renal perfusion indices, and postoperative acute kidney injury (AKI) in cardiac patients.

METHODS

In a prospective cohort study conducted at a single academic institution, we collected data from adult patients undergoing open-heart operations with cardiopulmonary bypass (CPB) at our institution from February 2022 to April 2022 using the Accuryn SmartFoley system® (Potrero Medical, Hayward, CA). Patients on mechanical support devices, pregnant patients, and patients on hemodialysis were excluded. Demographics, hemodynamics, and mean airway pressure (mAir) were measured at the beginning of the cardiac operations and during the first four hours of ICU. Renal perfusion indices were then calculated (mean perfusion pressure (MPP) = mean arterial pressure (MAP) - central venous pressure (CVP); abdominal perfusion pressure (APP) = MAP - IAP; and effective renal perfusion pressure (eRPP) = MAP - (CVP + mAir + IAP)). Length of stay (LOS) was measured from the day of surgery to ICU discharge (ICU LOS) and hospital discharge (hospital LOS).

RESULTS

During the first four hours of ICU stay, the non-AKI group had lower IAP and higher renal perfusion indices (MPP, APP, and eRPP). Logistic regression showed high perfusion pressures correlated with lower postoperative AKI (all OR <1, p<0.05). The postoperative AKI group also had significantly longer ICU LOS (7.33 vs. 4.57 days) and hospital LOS (17.0 vs. 10.2 days).

CONCLUSION

Renal perfusion indices are a promising tool to predict postoperative AKI in cardiac surgery patients.

Incidence of Hereditary Gastric Cancer May Be Much Higher than Reported

Hereditary gastric cancers (HGCs) are supposed to be rare and difficult to identify. Nonetheless, many cases of young patients with gastric cancer (GC) fulfill the clinical criteria for considering this diagnosis but do not present the defined pathogenic mutations necessary to meet a formal diagnosis of HGC. Moreover, GC in young people is a challenging medical situation due to the usual aggressiveness of such cases and the potential risk for their relatives when related to a germline variant. Aiming to identify additional germline alterations that might contribute to the early onset of GC, a complete exome sequence of blood samples from 95 GC patients under 50 and 94 blood samples from non-cancer patients was performed and compared in this study. The number of identified germline mutations in GC patients was found to be much higher than that from individuals without a cancer diagnosis. Specifically, the number of high functional impact mutations, including those affecting genes involved in medical diseases, cancer hallmark genes, and DNA replication and repair processes, was much higher, strengthening the hypothesis of the potential causal role of such mutations in hereditary cancers. Conversely, classically related HGC mutations were not found and the number of mutations in genes in the CDH1 pathway was not found to be relevant among the young GC patients, reinforcing the hypothesis that existing alternative germline contributions favor the early onset of GC. The LILRB1 gene variants, absent in the world's cancer datasets but present in high frequencies among the studied GC patients, may represent essential cancer variants specific to the Amerindian ancestry's contributions. Identifying non-reported GC variants, potentially originating from under-studied populations, may pave the way for additional discoveries and translations to clinical interventions for GC management. The newly proposed approaches may reduce the discrepancy between clinically suspected and molecularly proven hereditary GC and shed light on similar inconsistencies among other cancer types. Additionally, the results of this study may support the development of new blood tests for evaluating cancer risk that can be used in clinical practice, helping physicians make decisions about strategies for surveillance and risk-reduction interventions.

Second hit impels oncogenesis of retinoblastoma in patient-induced pluripotent stem cell-derived retinal organoids: direct evidence for Knudson's theory

Retinoblastoma (Rb) is a type of malignant tumor due to abnormal retinogenesis with biallelic mutations of the RB1 gene. Its pathogenesis has been proposed as a "two-mutation hypothesis" by Knudson since 1971; however, there remain some debates on disease onset sufficiency of the biallelic RB1 mutations. To obtain straightforward evidence for this hypothesis, we investigated whether two-hit mutations of the RB1 gene drive tumorigenesis in patient-induced pluripotent stem cell (hiPSC)-derived human retinal organoids (hROs) and whether single allelic mutation hiPSC-derived hROs exhibit molecular and cellular defects. We generated hiPSCs with a heterozygous germline mutation (RB1^{m1/ wt} ) from a Rb patient. A second-allele RB1 gene mutation was knocked in to produce compound heterozygous mutations (RB1^m1/m2 ) in the hiPSCs. These two hiPSC lines were independently developed into hROs through a stepwise differentiation. The hiPSC-RB1^m1/m2 derived organoids demonstrated tumorigenesis in dishes, consistent with Rb profiles in spatiotemporal transcriptomes, in which developmentally photoreceptor fate-determining markers, CRX and OTX2, were highly expressed in hiPSC-RB1^m1/m2 derived hROs. Additionally, ARR3⁺ maturing cone precursors were co-labeled with proliferative markers Ki67 or PCNA, in agreement with the consensus that human Rb is originated from maturing cone precursors. Finally, we demonstrated that retinal cells of hROs with monoallelic RB1 mutation were abnormal in molecular aspects due to its haploinsufficiency. In conclusion, this study provides straightforward supporting evidence in a way of reverse genetics for "two-hit hypothesis" in the Rb tumorigenesis and opens new avenues for development of early intervention and treatment of Rb.