Increased cancer risks in myotonic dystrophy

Muscleblind-like 1 suppresses breast cancer metastatic colonization and stabilizes metastasis suppressor transcripts

Post-transcriptional deregulation is a defining feature of metastatic cancer. While many microRNAs have been implicated as regulators of metastatic progression, less is known about the roles and mechanisms of RNA-binding proteins in this process. We identified muscleblind-like 1 (MBNL1), a gene implicated in myotonic dystrophy, as a robust suppressor of multiorgan breast cancer metastasis. MBNL1 binds the 3' untranslated regions (UTRs) of DBNL (drebrin-like protein) and TACC1 (transforming acidic coiled-coil containing protein 1)-two genes that we implicate as metastasis suppressors. By enhancing the stability of these genes' transcripts, MBNL1 suppresses cell invasiveness. Consistent with these findings, elevated MBNL1 expression in human breast tumors is associated with reduced metastatic relapse likelihood. Our findings delineate a post-transcriptional network that governs breast cancer metastasis through RNA-binding protein-mediated transcript stabilization.

Facioscapulohumeral dystrophy myoblasts efficiently repair moderate levels of oxidative DNA damage

Facioscapulohumeral dystrophy (FSHD) is a progressive muscular dystrophy linked to a deletion of a subset of D4Z4 macrosatellite repeats accompanied by a chromatin relaxation of the D4Z4 array on chromosome 4q. In vitro, FSHD primary myoblasts show altered expression of oxidative-related genes and are more susceptible to oxidative stress. Double homeobox 4 (DUX4) gene, encoded within each D4Z4 unit, is normally transcriptionally silenced but is found aberrantly expressed in skeletal muscles of FSHD patients. Its expression leads to a deregulation of DUX4 target genes including those implicated in redox balance. Here, we assessed DNA repair efficiency of oxidative DNA damage in FSHD myoblasts and DUX4-transfected myoblasts. We have shown that the DNA repair activity is altered neither in FSHD myoblasts nor in immortalized human myoblasts transiently expressing DUX4. DNA damage caused by moderate doses of an oxidant is efficiently repaired while FSHD myoblasts exposed for 24 h to high levels of oxidative stress accumulated more DNA damage than normal myoblasts, suggesting that FSHD myoblasts remain more vulnerable to oxidative stress at high doses of oxidants.

Increased risk of tumor in DM1 is not related to exposure to common lifestyle risk factors

Recent studies documented an increased risk of neoplasm in patients with myotonic dystrophies (DM). Yet, none of these studies evaluated the contribution of common cancer risk factors in such observation. In this study, we included a cohort of patients (n = 255) with an established molecular diagnosis of DM type 1 (DM1), and who receives their treatment in one of the four centers with recognized expertise in neuromuscular disorders in Rome. We estimated the prevalence of benign and malignant tumors, and assessed if lifestyle factors and/or specific disease features would be associated to their occurrence. Overall, 59 benign tumors in 54 patients and 19 malignant tumors in 17 patients were diagnosed. The most common malignant neoplasms were cancers of the skin (31.6%), thyroid (21.0%), ovary (10.5%), and breast (10.5%). Uterine fibroid was the most common benign tumor (37.6%) in women, while pilomatricoma was the most common in men (28.6%). Age at enrollment (OR = 1.02, 95% CI 1.00-1.05), and female gender (OR = 5.71, 95% CI 2.90-11.22) were associated with tumor development in DM1 patients, while thyroid disorders was associated with malignant tumors only in women (OR = 5.12, 95% CI 1.35-19.37). There was no association between tumor development and evaluated lifestyle factors. In conclusion, the lack of association between common cancer risk factors and tumor development in DM1 support a pathogenic link between tumors and DM1 itself, emphasizing the need for a systematic surveillance. Our observation of an association between thyroid diseases in women and cancer development needs confirmation.

Myotonic disorders: A review article

The myotonic disorders are a heterogeneous group of genetically determined diseases that are unified by the presence of myotonia, which is defined as failure of muscle relaxation after activation. The presentation of these disorders can range from asymptomatic electrical myotonia, as seen in some forms of myotonia congenita (MC), to severe disability with muscle weakness, cardiac conduction defects, and other systemic features as in myotonic dystrophy type I (DM1). In this review, we describe the clinical features and pathophysiology of the different myotonic disorders, their laboratory and electrophysiologic findings and briefly review the currently available treatments.

Brain tumors in patients with myotonic dystrophy: a population-based study

BACKGROUND AND PURPOSE

Patients with myotonic dystrophy (DM) are at high risk of brain cancer. This study describes the spectrum of brain neoplasms in DM patients.

METHODS

Data from 1119 DM patients identified from the National Swedish Patient Register between 1987 and 2007 were linked to the National Cancer and the Cause of Death Registers. Standardized incidence ratios (SIRs) and cumulative incidence to quantify the relative and absolute risks of brain neoplasms were calculated and the Kaplan-Meier estimator was used for survival analysis. Patient follow-up started at birth or the age at the start of Swedish cancer registration (1 January 1958) and ended at the age of brain neoplasm diagnosis, death or on 31 December 2007.

RESULTS

Twenty patients developed brain neoplasm during follow-up {median age 53, range 2-76 years, accounting for a five-fold excess risk of brain tumors during the patient lifetime [SIR = 5.4, 95% confidence interval (CI) 3.4-8.1, P = 1 × 10(-5) ]}. Astrocytoma was the most common histological subtype (n = 16, 80%), and almost all cases (n = 19) developed after age 20. No statistically significant differences in gender-specific risks (SIR in men 6.3 and in women 3.8, P-heterogeneity 0.46) were observed. After accounting for competing mortality related to DM, the cumulative incidence of brain neoplasms reached 2.9% (95% CI 1.8%-4.7%) by age 70. Five-year survival after brain tumor diagnosis was 52% (95%CI 29%-75%) overall (number at risk 8) and 34% (95% CI 26%-47%) for malignant neoplasms (number at risk 5).

CONCLUSION

Despite the high relative risk of DM-related brain tumors, the absolute risk is modest. Nonetheless, careful evaluation of DM patients with new central nervous system symptoms is warranted.

Dysplastic nevi, cutaneous melanoma, and other skin neoplasms in patients with myotonic dystrophy type 1: a cross-sectional study

BACKGROUND

Myotonic dystrophy type 1 (MD1) is reported to be associated with internal malignancies. The association of myotonic dystrophy with cutaneous tumors is not fully understood.

OBJECTIVE

We sought to explore the total nevi count and the presence of atypical nevi, cutaneous melanoma, and other skin neoplasms in a representative cohort of patients with MD1 and to compare the findings with age- and sex-matched control subjects.

METHODS

In all, 90 patients with MD1 and 103 age- and sex-matched control subjects were assessed for cutaneous neoplasms by clinical skin and epiluminescence examination (dermoscopy). Where indicated, subsequent excisions were performed. In patients with MD1, leukocyte n(CTG) expansion was measured.

RESULTS

Patients with MD1 showed significantly higher numbers of nevi, dysplastic nevi, and melanomas despite a significantly greater proportion of the control subjects reporting sunburns. In addition, we found a significantly greater number of pilomatrixoma in patients with MD1.

LIMITATIONS

Our study is limited by the fact that there is no agreed-upon standardized technique to assess for prior sun exposure. Further research in the association of cutaneous neoplasms and MD1 including vitamin D and molecular biological techniques are also recommended.

CONCLUSION

MD1 itself may predispose to development of skin tumors.

Myotonic dystrophy

Myotonic dystrophy (dystrophia myotonica, DM) is one of the most common lethal monogenic disorders in populations of European descent. DM type 1 was first described over a century ago. More recently, a second form of the disease, DM type 2 was recognized, which results from repeat expansion in a different gene. Both disorders have autosomal dominant inheritance and multisystem features, including myotonic myopathy, cataract, and cardiac conduction disease. This article reviews the clinical presentation and pathophysiology of DM and discusses current management and future potential for developing targeted therapies.

Cancer-related genes in the transcription signature of facioscapulohumeral dystrophy myoblasts and myotubes

Muscular dystrophy is a condition potentially predisposing for cancer; however, currently, only Myotonic dystrophy patients are known to have a higher risk of cancer. Here, we have searched for a link between facioscapulohumeral dystrophy (FSHD) and cancer by comparing published transcriptome signatures of FSHD and various malignant tumours and have found a significant enrichment of cancer-related genes among the genes differentially expressed in FSHD. The analysis has shown that gene expression profiles of FSHD myoblasts and myotubes resemble that of Ewing's sarcoma more than that of other cancer types tested. This is the first study demonstrating a similarity between FSHD and cancer cell expression profiles, a finding that might indicate the existence of a common step in the pathogenesis of these two diseases.

Quantifying cancer absolute risk and cancer mortality in the presence of competing events after a myotonic dystrophy diagnosis

Recent studies show that patients with myotonic dystrophy (DM) have an increased risk of specific malignancies, but estimates of absolute cancer risk accounting for competing events are lacking. Using the Swedish Patient Registry, we identified 1,081 patients with an inpatient and/or outpatient diagnosis of DM between 1987 and 2007. Date and cause of death and date of cancer diagnosis were extracted from the Swedish Cause of Death and Cancer Registries. We calculated non-parametric estimates of absolute cancer risk and cancer mortality accounting for the high non-cancer competing mortality associated with DM. Absolute cancer risk after DM diagnosis was 1.6% (95% CI=0.4-4%), 5% (95% CI=3-9%) and 9% (95% CI=6-13%) at ages 40, 50 and 60 years, respectively. Females had a higher absolute risk of all cancers combined than males: 9% (95% CI=4-14), and 13% (95% CI=9-20) vs. 2% (95%CI= 0.7-6) and 4% (95%CI=2-8) by ages 50 and 60 years, respectively) and developed cancer at younger ages (median age =51 years, range=22-74 vs. 57, range=43-84, respectively, p=0.02). Cancer deaths accounted for 10% of all deaths, with an absolute cancer mortality risk of 2% (95%CI=1-4.5%), 4% (95%CI=2-6%), and 6% (95%CI=4-9%) by ages 50, 60, and 70 years, respectively. No gender difference in cancer-specific mortality was observed (p=0.6). In conclusion, cancer significantly contributes to morbidity and mortality in DM patients, even after accounting for high competing DM mortality from non-neoplastic causes. It is important to apply population-appropriate, validated cancer screening strategies in DM patients.

Diagnostic odyssey of patients with myotonic dystrophy

The onset and symptoms of the myotonic dystrophies are diverse, complicating their diagnoses and limiting a comprehensive approach to their clinical care. This report analyzes the diagnostic delay (time from onset of first symptom to diagnosis) in a large sample of myotonic dystrophy (DM) patients enrolled in the US National Registry [679 DM type 1 (DM1) and 135 DM type 2 (DM2) patients]. Age of onset averaged 34.0 ± 14.1 years in DM2 patients compared to 26.1 ± 13.2 years in DM1 (p < 0.0001). The most common initial symptom in DM2 patients was leg weakness (32.6 %) compared to grip myotonia in DM1 (38.3 %). Pain was reported as the first symptom in 11.1 % of DM2 and 3.0 % of DM1 patients (p < 0.0001). Reaching the correct diagnosis in DM2 took 14 years on average (double the time compared to DM1) and a significantly higher percentage of patients underwent extended workup including electromyography, muscle biopsies, and finally genetic testing. DM patients who were index cases experienced similar diagnostic delays to non-index cases of DM. Further evaluation of how to shorten these diagnostic delays and limit their impact on burdens of disease, family planning, and symptom management is needed.

[Increasing risk of tumors in myotonic dystrophy type 1]

OBJECTIVE

Myotonic dystrophy type 1 (DM1) is characterized by an unstable expansion of a CTG repeat resulting in altered mRNA biogenesis. Benign or malignant tumours are increasingly reported. The aim of the study was to evaluate the risk of tumor in a cohort of patients DM1.

METHOD

We retrospectively reviewed the medical records of every DM1 patient admitted in our neuromuscular center. Diagnoses of cancer and age at diagnosis were noted. The relative risk of a selected cancer was calculated using the data of the cancer registry obtained from the French "Institut de Veille Sanitaire".

RESULTS

A total of 109 French DM1 patients, aged 44.1±13.0 years, were studied, and 14 malignant tumours were observed, with a significant relative risk (RR) of thymoma, of gynaecologic cancers, of lung cancers.

CONCLUSION

While this cohort is small, our findings nevertheless suggest an increased risk of particular cancers in DM1. The toxic effects of mutant RNA may possibly affect oncogene expression or growth factor signalling pathways in cells. Clinical practice should include cancer screening and prevention of risk factors in DM1 patients.

CELFish ways to modulate mRNA decay

The CELF family of RNA-binding proteins regulates many steps of mRNA metabolism. Although their best characterized function is in pre-mRNA splice site choice, CELF family members are also powerful modulators of mRNA decay. In this review we focus on the different modes of regulation that CELF proteins employ to mediate mRNA decay by binding to GU-rich elements. After starting with an overview of the importance of CELF proteins during development and disease pathogenesis, we then review the mRNA networks and cellular pathways these proteins regulate and the mechanisms by which they influence mRNA decay. Finally, we discuss how CELF protein activity is modulated during development and in response to cellular signals. We conclude by highlighting the priorities for new experiments in this field. This article is part of a Special Issue entitled: RNA Decay mechanisms.

Correlates of tumor development in patients with myotonic dystrophy

Patients with myotonic dystrophy (DM) have recently been reported to be at increased risk of tumor development, but clinical associations related to this observation are unknown. We calculated the odds ratios (ORs) and 95 % confidence intervals (CI) of self-reported tumor development by patients' demographic and clinical characteristics to evaluate factors associated with tumor development in DM patients, using data from the National Registry of Myotonic Dystrophy and Facioscapulohumeral Dystrophy Patients and Family Members. Of the 911 participants, 47.5 % were male and 85.7 % had DM type 1 (DM1). Compared to DM1, patients with DM type 2 (DM2) were older at registry enrollment (median age 55 vs. 44 years, p < 0.0001) and at DM diagnosis (median age 48 vs. 30 years, p < 0.0001); and more likely to be females (p = 0.001). At enrollment, 95 (10.4 %) DM patients reported a history of benign or malignant tumor. Tumors were associated with female gender (OR 1.9, 95 % CI 1.2-3.1, p = 0.007) and DM1 (OR 2.1, 95 % CI 1.1-4.1, p = 0.03). In a subgroup analysis of patients with blood-based DNA testing results (397 DM1, 54 DM2), repeat expansion size was not associated with tumor risk in DM1 (p = 0.26) or DM2 (p = 0.34). In conclusion, female gender and DM1 subtype, but not DNA repeat expansion size, were associated with increased risk of tumors in DM. Follow-up studies are warranted to determine if oncogenes associated with dystrophia myotonica-protein kinase are altered in DM, and to determine if repeat expansion size, as in our study, is not associated with tumor development.