Inherited disposition to cardiac myxoma development

Resolving the heterogeneous tumour microenvironment in cardiac myxoma through single-cell and spatial transcriptomics

BACKGROUND

Cardiac myxoma (CM) is the most common (58%-80%) type of primary cardiac tumours. Currently, there is a need to develop medical therapies, especially for patients not physically suitable for surgeries. However, the mechanisms that shape the tumour microenvironment (TME) in CM remain largely unknown, which impedes the development of targeted therapies. Here, we aimed to dissect the TME in CM at single-cell and spatial resolution.

METHODS

We performed single-cell transcriptomic sequencing and Visium CytAssist spatial transcriptomic (ST) assays on tumour samples from patients with CM. A comprehensive analysis was performed, including unsupervised clustering, RNA velocity, clonal substructure inference of tumour cells and cell-cell communication.

RESULTS

Unsupervised clustering of 34 759 cells identified 12 clusters, which were assigned to endothelial cells (ECs), mesenchymal stroma cells (MSCs), and tumour-infiltrating immune cells. Myxoma tumour cells were found to encompass two closely related phenotypic states, namely, EC-like tumour cells (ETCs) and MSC-like tumour cells (MTCs). According to RNA velocity, our findings suggest that ETCs may be directly differentiated from MTCs. The immune microenvironment of CM was found to contain multiple factors that promote immune suppression and evasion, underscoring the potential of using immunotherapies as a treatment option. Hyperactive signals sent primarily by tumour cells were identified, such as MDK, HGF, chemerin, and GDF15 signalling. Finally, the ST assay uncovered spatial features of the subclusters, proximal cell-cell communication, and clonal evolution of myxoma tumour cells.

CONCLUSIONS

Our study presents the first comprehensive characterisation of the TME in CM at both single-cell and spatial resolution. Our study provides novel insight into the differentiation of myxoma tumour cells and advance our understanding of the TME in CM. Given the rarity of cardiac tumours, our study provides invaluable datasets and promotes the development of medical therapies for CM.

The tumor microenvironment may trigger lymphoproliferation in cardiac myxoma

Cardiac myxomas (CM) and primary cardiac lymphoproliferative disorders (LPD) are rare primary cardiac neoplasms. The composite occurrence of LPD in CM has been occasionally reported, and chronic inflammation in response to viral infection has been suggested to be at the basis of oncogenesis. Cancers can upregulate autophagy to endure microenvironmental stress and to increase local growth and aggressiveness. CM exhibit a dichotomous separation in low and high inflammatory grades (LIG vs. HIG). We studied 23 CMs using autophagy-related proteins and NanoString technology for gene expression. Autophagy-related proteins (Beclin-1, LAMP-1, LC3, and p62) were demonstrated in both tumor and stromal cells. ATG genes showed a progression of involvement in CM using an 8-gene signature. They were associated with Epstein-Barr virus (EBV) encoded latent membrane protein 1 (EBV LMP1) activation. We suggest that CM can upregulate autophagy, creating a favorable environment for EBV-driven oncogenesis. To the best of our knowledge, the present study is the first to report on the TME using the expression of autophagy-related genes and proteins in CM. The microenvironment of CM is dynamic, with a variety of cell types and different molecular pathways at play, and this study may clearly warrant further investigation.

Recurrent cardiac intimal sarcoma misdiagnosed as a myxoma or malignant transformation of a cardiac myxoma?

Cardiac intimal sarcoma is extremely rare and aggressive primary malignant cardiac tumors. Here, we reported the case of a young man initially operated for a tumor of the left atrium, causing a dynamic obstruction of the mitral valve and (mis-)diagnosed as a myxoma at the histopathological analysis. Patient presented a local recurrence at 3 months and was reoperated. Pathology revealed this time the presence of an intimal sarcoma. Patient received adjuvant chemotherapy. Despite a good local control, the 1-year follow-up positron emission tomography scan revealed the presence of a metastasis in the left adrenal gland that was surgically resected. This article aims to highlight the risk of misdiagnosis in case of cardiac tumors, the hypothetical concept of malignant transformation of a cardiac myxoma, the aggressive course of the extremely rare cardiac intimal sarcoma, and the therapeutic modalities available to treat this pathology.

Primary melanotic tumors of the nervous system: a consecutive case series

BACKGROUND AND PURPOSE

Primary melanotic tumors of the nervous system (PMTNS) are thought to be an exceedingly rare group of tumors not captured by tumor registries. We aimed to determine relative incidence, clinical presentation, diagnostic findings, patient management, and outcome.

METHODS

We retrospectively searched the database of the Section of Neuro-Oncology at the Yale Cancer Center for patients with primary or metastatic melanotic lesions of the nervous system. For patients with PMTNS, we recorded demographic data, clinical presentation, histopathological and imaging findings, therapy, and outcome.

RESULTS

A total of 116 patients with melanotic lesions were identified, including four patients with PMTNS. The relative incidence of PMTNS was therefore calculated as 3.4%. Histology of PMTNS patients revealed melanocytoma in three patients and psammomatous melanotic schwannoma in one patient. Symptoms were non-specific and attributed to tumor mass effect. Magnetic resonance imaging showed hyperintensity on pre-contrast T1-weighted imaging, hypointensity on T2-weighted imaging, and homogenous contrast enhancement in all PMTNS patients. Definitive diagnosis was based on tissue analysis, with detection of melanin-containing cells on conventional histology and S100-positivity on immunohistochemistry. Molecular analysis for GNAQ^Q209L mutation assisted in establishing diagnosis when only small amounts of tissue were available. Aggressive surgical treatment showed favorable outcomes in all cases; radiation therapy was used for residual or relapsed disease. The median follow-up was 7.5 ± 5 years, and all patients were alive on the day of database closure.

CONCLUSION

Primary melanotic tumors of the nervous system are rare nervous system tumors. Outcome appears excellent, and complete surgical resection may form the basis for favorable outcome. Radiation therapy may represent a therapeutic approach for residual or relapsed disease.

GPER-induced signaling is essential for the survival of breast cancer stem cells

G protein-coupled estrogen receptor-1 (GPER), a member of the G protein-coupled receptor (GPCR) superfamily, mediates estrogen-induced proliferation of normal and malignant breast epithelial cells. However, its role in breast cancer stem cells (BCSCs) remains unclear. Here we showed greater expression of GPER in BCSCs than non-BCSCs of three patient-derived xenografts of ER- /PR+ breast cancers. GPER silencing reduced stemness features of BCSCs as reflected by reduced mammosphere forming capacity in vitro, and tumor growth in vivo with decreased BCSC populations. Comparative phosphoproteomics revealed greater GPER-mediated PKA/BAD signaling in BCSCs. Activation of GPER by its ligands, including tamoxifen (TMX), induced phosphorylation of PKA and BAD-Ser118 to sustain BCSC characteristics. Transfection with a dominant-negative mutant BAD (Ser118Ala) led to reduced cell survival. Taken together, GPER and its downstream signaling play a key role in maintaining the stemness of BCSCs, suggesting that GPER is a potential therapeutic target for eradicating BCSCs.

Clinical features and surgical results of cardiac myxoma in Carney complex

BACKGROUND

We sought to analyze clinical features and surgical results of 10 cases of cardiac myxomas in Carney complex (CNC).

METHODS

Between January 2003 and December 2013, 10 patients with cardiac myxomas in CNC underwent surgical resection. Associated cardiac lesions included moderate and severe mitral regurgitation in two cases, and moderate tricuspid regurgitation in one case. Age, gender, the incidence of arterial embolism, the rate of multiple cardiac myxomas, and the recurrence rate after resections of cardiac myxoma were compared between isolated cardiac myxomas and cardiac myxomas in CNC.

RESULTS

The incidence of cardiac myxoma in CNC was 1.74% (10/574). There were no deaths following surgery. There was one late death due to cerebral embolism 40 months following a reoperation (10%). A significant difference was found in the age, the incidence of arterial embolism, the rate of multiple cardiac myxomas, and the recurrence rate after resection of cardiac myxoma between cardiac myxoma in CNC and isolated cardiac myxoma (P < 0.05). There was no significant difference in gender between cardiac myxoma in CNC and isolated cardiac myxoma (P > 0.05).

CONCLUSIONS

Complex myxomas in CNS present at an earlier age, are more prevalent in women than in men, are more often multicentric, with a higher rate of arterial embolism and a high recurrence rate after resection. Close follow-up for cardiac myxoma in CNC after surgery is necessary due to the high recurrence rate.

The First Manifestation of a Left Atrial Myxoma as a Consequence of Multiple Left Coronary Artery Embolisms

A case of multiple embolisms in the left coronary artery as a rare first manifestation of left atrial myxoma is reported. A patient with embolic myocardial infarction and congestive heart failure was treated by percutaneous aspirations and balloon dilatations. Transesophageal echocardiography disclosed a villous myxoma with high embolic potential. Surgical resection of the tumour, suturing of a patent foramen ovale suture and an annuloplasty of the dilated tricuspid annulus was performed the third day after the admission. Recovery of the documented left ventricular systolic function can be explained by resorption of myxomatous material. The patient was discharged ten days after the surgery.

Association between herpes simplex virus Types 1 and 2 with cardiac myxoma

Most cases of atrial myxoma are sporadic, and the exact etiology is unknown. We examined if herpes simplex virus (HSV)-1 and HSV-2 antigens and/or DNA could be detected in a cohort of Iranian patients with cardiac myxomas. From July 2004 to June 2014, among a total of 36,703 patients undergoing open heart surgeries, consecutive patients with cardiac myxoma who were treated by surgical excision at our center included in this study. Of 73 patients studied, 56% were female with a mean age of 54 years (ranging from 23 to 77 years). Seventy-four myxomas were surgically removed from 73 patients, since one patient had two myxomas which were located on both the right atrium and right ventricle. The materials for this analysis were retrospectively gathered from extracted tumors that stored in a pathology bank of tissue paraffin blocks. The formalin fixed paraffin embedded tissue samples were investigated for HSV genomic DNA by both immunohistochemistry (IHC) and polymerase chain reaction (PCR) analysis. In all 74 cases there was no presence of HSV 1 and HSV 2 infection. This suggests that HSV may not play a role in sporadic cardiac myxomas; however, evidence for such association is currently lacking, and further studies are required to determine such a role.

Molecular Characteristics and Clinical Significance of 12 Fusion Genes in Acute Promyelocytic Leukemia: A Systematic Review

Acute promyelocytic leukemia (APL) is characterized by the generation of the promyelocytic leukemia-retinoic acid (RA) receptor α (PML-RARα) fusion gene. PML-RARα is the central leukemia-initiating event in APL and is directly targeted by all-trans-RA (ATRA) as well as arsenic. In classic APL harboring PML-RARα transcripts, more than 90% of patients can achieve complete remission when treated with ATRA combined with arsenic trioxide chemotherapy. In the last 20 years, more than 10 variant fusion genes have been found and identified in APL patients. These variant APL cases present different clinical phenotypes and treatment outcomes. All variant APL cases show a similar breakpoint within the RARα gene, whereas its partner genes are variable. These fusion proteins have the ability to repress rather than activate retinoic targets. These chimeric proteins also possess different molecular characteristics, thereby resulting in variable sensitivities to ATRA and clinical outcomes. In this review, we comprehensively analyze various rearrangements in variant APL cases that have been reported in the literature as well as the molecular characteristics and functions of the fusion proteins derived from different RARα partner genes and their clinical implications.

An unusual biatrial cardiac myxoma in a young patient

This is a report of a biatrial cardiac myxoma in a young man with a 10-month history of exertional dyspnea and palpitation. The echocardiogram revealed biatrial myxoma prolapsing through the mitral and tricuspid valves during diastole. All cardiac chambers were enlarged and dysfunctional. The electrocardiogram revealed a rapid ventricular response with atrial flutter rhythm. The masses were resected and diagnosed as myxoma by a histological examination. The follow-up echocardiogram revealed significant improvement in ventricular function and reduction in the cardiac chambers' volume. There was no evidence of myxoma recurrence. The most probable cause of the patient's heart failure was considered to be tachycardia-induced cardiomyopathy.

PRKAR1A in the development of cardiac myxoma: a study of 110 cases including isolated and syndromic tumors

Cardiac myxoma usually occurs as a solitary mass, but occasionally develops as part of a familial syndrome, the Carney complex (CNC). Two thirds of CNC-associated cardiac myxomas exhibit mutations in PRKAR1A. PRKAR1A mutations occur in both familial and sporadic forms of CNC but have not been described in isolated (nonsyndromic) cardiac myxomas. A total of 127 consecutive cardiac myxomas surgically resected at Mayo Clinic (1993 to 2011) from 110 individuals were studied. Clinical, radiologic, and pathologic findings were reviewed. Of these, 103 patients had isolated cardiac myxomas, and 7 patients had the tumor as a component of CNC. Age and sex distributions were different for CNC (mean 26 y, range 14 to 44 y, 71% female) and non-CNC (mean 62 y, range 18 to 92 y, 63% female) patients. PRKAR1A immunohistochemical analysis (IHC) was performed, and myxoma cell reactivity was graded semiquantitatively. Bidirectional Sanger sequencing was performed in 3 CNC patients and 29 non-CNC patients, to test for the presence of mutations in all coding regions and intron/exon boundaries of the PRKAR1A gene. IHC staining showed that all 7 CNC cases lacked PRKAR1A antigenicity and that 33 (32%) isolated cardiac myxomas were similarly nonreactive. Of tumors subjected to sequencing analysis, 2 (67%) CNC myxomas and 9 (31%) non-CNC myxomas had pathogenic PRKAR1A mutations. No germline mutations were found in 4 non-CNC cases tested. PRKAR1A appears to play a role in the development of both syndromic and nonsyndromic cardiac myxomas. Routine IHC evaluation of cardiac myxomas for PRKAR1A expression may be useful in excluding a diagnosis of CNC.

Molecular basis of cardiac myxomas

Cardiac tumors are rare, and of these, primary cardiac tumors are even rarer. Metastatic cardiac tumors are about 100 times more common than the primary tumors. About 90% of primary cardiac tumors are benign, and of these the most common are cardiac myxomas. Approximately 12% of primary cardiac tumors are completely asymptomatic while others present with one or more signs and symptoms of the classical triad of hemodynamic changes due to intracardiac obstruction, embolism and nonspecific constitutional symptoms. Echocardiography is highly sensitive and specific in detecting cardiac tumors. Other helpful investigations are chest X-rays, magnetic resonance imaging and computerized tomography scan. Surgical excision is the treatment of choice for primary cardiac tumors and is usually associated with a good prognosis. This review article will focus on the general features of benign cardiac tumors with an emphasis on cardiac myxomas and their molecular basis.

Surgery for Primary Cardiac Tumors in Children

Background—

To evaluate indications and results of surgery for primary cardiac tumors in children.

Methods and Results—

Eighty-nine patients aged ≤18 years undergoing surgery for cardiac tumor between 1990 and 2005 from 16 centers were included retrospectively (M/F=41/48; median age 4.3 months, range 1 day to 18 years). Sixty-three patients (68.5%) presented with symptoms. Surgery consisted of complete resection in 62 (69.7%) patients, partial resection in 21 (23.6%), and cardiac transplant in 4 (4.5%). Most frequent histotypes (93.2%) were benign (rhabdomyoma, myxoma, teratoma, fibroma, and hemangioma). Postoperative complications occurred in 29.9%. Early and late mortality were 4.5% each (mean follow-up, 6.3±4.4 years); major adverse events occurred in 28.2% of the patients; 90.7% of patients are in New York Heart Association class I. There were no statistically significant differences in survival, postoperative complications, or adverse events after complete and partial resection in benign tumors other than myxomas. Cardiac transplant was associated significantly with higher mortality rate ( P= 0.006). Overall mortality was associated to malignancy ( P =0.0008), and adverse events during follow-up ( P =0.005).

Conclusions—

Surgery for primary cardiac tumors in children has good early and long-term outcomes, with low recurrence rate. Rhabdomyomas are the most frequent surgical histotypes. Malignant tumors negatively affect early and late survival. Heart transplant is indicated when conservative surgery is not feasible. Lack of recurrence after partial resection of benign cardiac tumors indicates that a less risky tumor debulking is effective for a subset of histotypes such as rhabdomyomas and fibromas.

Systemic Embolization and Myocardial Infarction due to Clinically Unrecognized Left Atrial Myxoma

Myxomas are the most common primary tumors of the heart. We report an extraordinary severe case of left atrial myxoma, presenting with stroke, myocardial infarction, and multiple arterial embolism including aorta, splenic and renal arteries, and several peripheral arteries. The patient had previously been diagnosed with systemic vasculitis, a typical but less common finding caused by multiple emboli mimicking vasculitis. The myxoma was removed and atrial septum reconstruction was performed. In summary, early diagnostic differentiation of myxoma from vasculitis is critical, and immediate surgical removal of myxoma is required as the probability of thromboembolic complications increases over time.

Systemic Embolization and Myocardial Infarction due to Clinically Unrecognized Left Atrial Myxoma

Myxomas are the most common primary tumors of the heart. We report an extraordinary severe case of left atrial myxoma, presenting with stroke, myocardial infarction, and multiple arterial embolism including aorta, splenic and renal arteries, and several peripheral arteries. The patient had previously been diagnosed with systemic vasculitis, a typical but less common finding caused by multiple emboli mimicking vasculitis. The myxoma was removed and atrial septum reconstruction was performed. In summary, early diagnostic differentiation of myxoma from vasculitis is critical, and immediate surgical removal of myxoma is required as the probability of thromboembolic complications increases over time.

Management of cardiac myxoma during pregnancy: a case series and review of the literature

Cardiac myxomas are the most common primary benign tumors of the heart. The reported incidence during pregnancy is extremely low with only 17 reported cases in the medical literature. Standard therapy involves surgical resection given the potential for embolization. In the pregnant patient, however, the risks of embolization must be balanced against the risk of cardiopulmonary bypass to the mother and the fetus. We present two cases of cardiac myxoma diagnosed during pregnancy and review the presentation and management strategies of previously reported cases. In conclusion, successful surgical resection of the myxomas during pregnancy was performed in both of our cases. Given the rarity of cases, individual multidisciplinary assessment and management strategies are essential.

Leukemic transformation by the APL fusion protein PRKAR1A-RARα critically depends on recruitment of RXRα

PRKAR1A (R1A)–retinoic acid receptor-α (R1A-RARα) is the sixth RARα–containing fusion protein in acute promyelocytic leukemia (APL). Using the murine bone-marrow retroviral transduction/transformation assay, we showed that R1A-RARα fusion protein could transform bone-marrow progenitor/stem cells. In gel-shift assays, R1A-RARα was able to bind to a panel of retinoic acid response elements both as a homodimer and as a heterodimer with RXRα, and demonstrated distinct DNA-binding characteristics compared with wild-type RARα/RXRα or other X-RARα chimeric proteins. The ratio of R1A-RARα to RXRα proteins affected the retinoic acid response element interaction pattern of R1A-RARα/RXRα complexes. Studies comparing R1A-RARα with R1A-RARα(ΔRIIa) demonstrated that the RIIa protein interaction domain located within R1A was responsible for R1A-RARα homodimeric DNA binding and interaction with wild-type R1A protein. However, the RIIa domain was not required for R1A-RARα–mediated transformation because its deletion in R1A-RARα(ΔRIIa) did not compromise its transformation capability. In contrast, introduction of point mutations within the RARα portion of either R1A-RARα or R1A-RARα(ΔRIIa), previously demonstrated to eliminate RXRα interaction or treatment of transduced cells with RXRα shRNA or a RXRα agonist, reduced transformation capability. Thus, leukemic transformation by APL fusion protein PRKAR1A-RARα is critically dependent on RXRα, which suggests RXRα is a promising target for APL.

A-kinase anchoring proteins: from protein complexes to physiology and disease

Protein scaffold complexes are a key mechanism by which a common signaling pathway can serve many different functions. Sequestering a signaling enzyme to a specific subcellular environment not only ensures that the enzyme is near its relevant targets, but also segregates this activity to prevent indiscriminate phosphorylation of other substrates. One family of diverse, well-studied scaffolding proteins are the A-kinase anchoring proteins (AKAPs). These anchoring proteins form multi-protein complexes that integrate cAMP signaling with other pathways and signaling events. In this review, we focus on recent advances in the elucidation of AKAP function.

Cardiac myxoma presenting with sensory neuropathy

A 51-year-old man was admitted for burning dysesthesias over the soles. Neurologic examination showed a pansensory loss over both feet associated with weakness of toes dorsiflexion. Motor conduction study of the sural nerve showed a significant reduction of nerve conduction velocity (21.4 m/s) suggesting a demyelinating neuropathy. In the following days he was referred to the cardiologist because of the sudden onset of a rapid atrial tachycardia, which was terminated by adenosine. Echocardiography showed a left atrial mass arising from the atrial septum consistent with the diagnosis of cardiac myxoma. The patient underwent cardiac surgery to remove the tumor, which was confirmed a myxoma by pathology. In the days following cardiac mass removal, neurological symptoms progressively disappeared in the absence of anti-inflammatory and steroid therapy and control motor conduction study showed complete normalization of nerve conduction velocity (54.5 m/s). Peripheral demyelinating neuropathy represented the first clinical presentation of cardiac myxoma in our patient and should be included among the possible paraneoplastic manifestations of this cardiac tumor.

Case report of familial Carney complex due to novel frameshift mutation c.597del C (p.Phe200LeufsX6) in PRKAR1A

Carney complex is an autosomal dominantly inherited disease characterized by skin pigmentation, myxoma, primary pigmented nodular adrenocortical disease (PPNAD), and acromegaly. However, only a few incidences of PPNAD combined with acromegaly are observed in patients. The type 1alpha regulatory subunit of cAMP-dependent protein kinase (PRKAR1A) has been identified in patients as a causative gene for Carney complex by a positional cloning approach. Here, we report a female patient diagnosed with Cushing's syndrome and a GH-producing pituitary adenoma without otherwise evident acromegaly that could be diagnosed only by specialized endocrinological tests. Based on family history of acromegaly (mother and sister) and the fact that the combination of both diseases is very rare, genetic diagnosis involving Carney complex was considered to be appropriate. The 10 exons and flanking regions of PRKAR1A were screened for mutations by direct DNA sequencing. The patient and her mother and sister were found to have the same, novel frameshift mutation resulting from a single base deletion in exon 6 coding cAMP-binding domain A, denoted c.597delC in PRKAR1A. This single base deletion generated an immature stop codon at the sixth codon (p.Phe200LeufsX6). Even family members with the same mutation can show distinct phenotypes, suggesting that Carney complex is a multifactorial disorder comprising various genetic and environmental factors. Genetic diagnosis makes it possible to prepare more effective therapeutic strategies for patients and gene carriers and to avoid unnecessary tests for non-carriers in the family of the patient.