Immunohistochemical analysis of a muscle ankyrin-repeat protein, Arpp, in paraffin-embedded tumors: evaluation of Arpp as a tumor marker for rhabdomyosarcoma

ANKRD2 Knockdown as a Therapeutic Strategy in Osteosarcoma: Effects on Proliferation and Drug Response in U2OS and HOS Cells

Ankrd2, a mechanoresponsive protein primarily studied in muscle physiology, is emerging as a player in cancer progression. This study investigates the functional role of Ankrd2 in osteosarcoma cells, revealing its critical involvement in cell proliferation and response to chemotherapeutic drugs. We showed that Ankrd2 knockdown impairs the activation of PI3K/Akt and ERK1/2 pathways, reduces levels of cell cycle regulators including cyclin D1 and cyclin B, and counteracts the expression of nuclear lamin A and lamin B, disrupting nuclear morphology and DNA integrity. Strikingly, the loss of Ankrd2 enhances the sensitivity of osteosarcoma cells to doxorubicin and cisplatin, highlighting Ankrd2 potential as a therapeutic target to improve chemotherapeutic efficacy. Defining a novel mechanistic role for Ankrd2 in promoting tumor progression, we propose that Ankrd2 reduction could be exploited as an adjuvant strategy to enhance the efficacy of chemotherapy, offering new therapeutic opportunities for OS treatment.

Adult Laryngeal Pleomorphic Rhabdomyosarcoma: A Rare Entity

Rhabdomyosarcoma (RMS) is a rare and aggressive cancerous tumor that arises from embryonal mesenchymal cells with skeletal muscle differentiation, and it is exceedingly rare that occurs specifically in the larynx. To date, only 22 instances of laryngeal pleomorphic RMSs have been documented in adults. Consequently, there is limited information available to assist healthcare professionals in effectively handling RMS in the larynx of adult patients. Here, we present an uncommon occurrence involving a 45-year-old man who experienced progressive hoarseness and received a diagnosis of pleomorphic RMS affecting the larynx. Pleomorphic RMS had been pathologically diagnosed after a vertical hemilaryngectomy. Following the surgical intervention, the patient underwent chemotherapy and radiation therapy. As of now, there have been no indications of tumor recurrence.

Alveolar rhabdomyosarcoma of epididymis: A case report

Rhabdomyosarcoma (RMS) is a soft tissue tumor, which is the most common in the head, neck, limbs, and trunk. RMS originating from the epididymis is extremely rare. Herein, we reported a 34-year-old patient with RMS on the right epididymis. For this case, right epididymal mass resection was performed and intraoperative freezing suggested a malignant tumor. Right testicular radical resection was subsequently adopted, with right epididymal alveolar RMS being pathologically diagnosed. Alternating VAC/VI chemotherapy was given after surgery, and tumor recurrence has not been found so far.

[Clinical analysis of testicular rhabdomyosarcoma]

Testicular rhabdomyosarcoma is relatively rare in testicular tumors, but the age of patient is relatively young and the degree of malignancy is high. Therefore, this article introduces 4 cases of testicular rhabdomyosarcoma who were admitted to Peking University Third Hospital from May 1994 to February 2019, and reviews the literature to improve the diagnosis and treatment of this disease. The average age of the 4 patients was 17.5 years (14-21 years), the average hospital stay was 22.0 d (17-31 d), and the average body mass index was 19.6 kg/m² (14.7-25.8 kg/m²). All the patients underwent routine preoperative blood and urine routine, biochemical tests, as well as serum tumor markers. Preoperative examinations also included chest radiograph, electrocardiogram, ultrasound of the scrotum and groin, and abdominal enhanced CT. Lung CT or other examinations were performed if necessary. The median serum human chorionic gonadotropin (HCG) of the 4 patients was 0.20 IU/L (0.06-0.86 IU/L) (all normal), and the median serum alpha-fetoprotein (AFP) was 1.03 g/L (0.65-1.66 g/L) (all normal). The average maximum diameter of the tumor was 10.0 cm (4.5-15.0 cm). Testicular rhabdomyosarcoma was mainly diagnosed by pathology. The main treatment was radical orchiectomy combined with retroperitoneal lymph node dissection, with or without postoperative adjuvant chemotherapy. The clinical manifestations of the patients with testicular rhabdomyosarcoma had no specific characteristics, but most patients were young at onset with mainly painless masses in the testicles, which were already large when they were found. Patients with testicular rhabdomyosarcoma have a poor prognosis, most of whom recur within two years. Because of the small number of cases of testicular rhabdomyosarcoma, there is no standard treatment currently. It is recommended that patients with testicular rhabdomyosarcoma undergo radical testicular resection combined with retroperitoneal lymph node dissection. Retroperitoneal lymph node metastasis is an important prognostic factor, and patients with postoperative adjuvant chemotherapy can still survive for a longer time. If local recurrence or limited metastasis is found after operation, local resection and salvage radiotherapy are feasible.

Ectopic Expression of Ankrd2 Affects Proliferation, Motility and Clonogenic Potential of Human Osteosarcoma Cells

Ankrd2 is a protein known for being mainly expressed in muscle fibers, where it participates in the mechanical stress response. Since both myocytes and osteoblasts are mesenchymal-derived cells, we were interested in examining the role of Ankrd2 in the progression of osteosarcoma which features a mechano-stress component. Although having been identified in many tumor-derived cell lines and -tissues, no study has yet described nor hypothesized any involvement for this protein in osteosarcoma tumorigenesis. In this paper, we report that Ankrd2 is expressed in cell lines obtained from human osteosarcoma and demonstrate a contribution by this protein in the pathogenesis of this insidious disease. Ankrd2 involvement in osteosarcoma development was evaluated in clones of Saos2, U2OS, HOS and MG63 cells stably expressing Ankrd2, through the investigation of hallmark processes of cancer cells. Interestingly, we found that exogenous expression of Ankrd2 influenced cellular growth, migration and clonogenicity in a cell line-dependent manner, whereas it was able to improve the formation of 3D spheroids in three out of four cellular models and enhanced matrix metalloproteinase (MMP) activity in all tested cell lines. Conversely, downregulation of Ankrd2 expression remarkably reduced proliferation and clonogenic potential of parental cells. As a whole, our data present Ankrd2 as a novel player in osteosarcoma development, opening up new therapeutic perspectives.

Multi-tasking role of the mechanosensing protein Ankrd2 in the signaling network of striated muscle

BACKGROUND

Ankrd2 (also known as Arpp) together with Ankrd1/CARP and DARP are members of the MARP mechanosensing proteins that form a complex with titin (N2A)/calpain 3 protease/myopalladin. In muscle, Ankrd2 is located in the I-band of the sarcomere and moves to the nucleus of adjacent myofibers on muscle injury. In myoblasts it is predominantly in the nucleus and on differentiation shifts from the nucleus to the cytoplasm. In agreement with its role as a sensor it interacts both with sarcomeric proteins and transcription factors.

METHODOLOGY/PRINCIPAL FINDINGS

Expression profiling of endogenous Ankrd2 silenced in human myotubes was undertaken to elucidate its role as an intermediary in cell signaling pathways. Silencing Ankrd2 expression altered the expression of genes involved in both intercellular communication (cytokine-cytokine receptor interaction, endocytosis, focal adhesion, tight junction, gap junction and regulation of the actin cytoskeleton) and intracellular communication (calcium, insulin, MAPK, p53, TGF-β and Wnt signaling). The significance of Ankrd2 in cell signaling was strengthened by the fact that we were able to show for the first time that Nkx2.5 and p53 are upstream effectors of the Ankrd2 gene and that Ankrd1/CARP, another MARP member, can modulate the transcriptional ability of MyoD on the Ankrd2 promoter. Another novel finding was the interaction between Ankrd2 and proteins with PDZ and SH3 domains, further supporting its role in signaling. It is noteworthy that we demonstrated that transcription factors PAX6, LHX2, NFIL3 and MECP2, were able to bind both the Ankrd2 protein and its promoter indicating the presence of a regulatory feedback loop mechanism.

CONCLUSIONS/SIGNIFICANCE

In conclusion we demonstrate that Ankrd2 is a potent regulator in muscle cells affecting a multitude of pathways and processes.

Anchoring skeletal muscle development and disease: the role of ankyrin repeat domain containing proteins in muscle physiology

The ankyrin repeat is a protein module with high affinity for other ankyrin repeats based on strong Van der Waals forces. The resulting dimerization is unusually resistant to both mechanical forces and alkanization, making this module exceedingly useful for meeting the extraordinary demands of muscle physiology. Many aspects of muscle function are controlled by the superfamily ankyrin repeat domain containing proteins, including structural fixation of the contractile apparatus to the muscle membrane by ankyrins, the archetypical member of the family. Additionally, other ankyrin repeat domain containing proteins critically control the various differentiation steps during muscle development, with Notch and developmental stage-specific expression of the members of the Ankyrin repeat and SOCS box (ASB) containing family of proteins controlling compartment size and guiding the various steps of muscle specification. Also, adaptive responses in fully formed muscle require ankyrin repeat containing proteins, with Myotrophin/V-1 ankyrin repeat containing proteins controlling the induction of hypertrophic responses following excessive mechanical load, and muscle ankyrin repeat proteins (MARPs) acting as protective mechanisms of last resort following extreme demands on muscle tissue. Knowledge on mechanisms governing the ordered expression of the various members of superfamily of ankyrin repeat domain containing proteins may prove exceedingly useful for developing novel rational therapy for cardiac disease and muscle dystrophies.

MARP Protein Family: A Possible Role in Molecular Mechanisms of Tumorigenesis

The MARP (muscle ankyrin repeat protein) family comprises three structurally similar proteins: CARP/Ankrd1, Ankrd2/Arpp and DARP/Ankrd23. They share four conserved copies of 33-residue ankyrin repeats and contain a nuclear localization signal, allowing the sorting of MARPs to the nucleus. They are found both in the nucleus and in the cytoplasm of skeletal and cardiac muscle cells, suggesting that MARPs shuttle within the cell enabling them to play a role in signal transduction in striated muscle. Expression of MARPs is altered under different pathological conditions. In skeletal muscle, CARP/Ankrd1 and Ankrd2/Arpp are up-regulated in muscle in patients suffering from Duchene muscular dystrophy, congenital myopathy and spinal muscular atrophy. Mutations inAnkrd1gene (coding CARP/Ankrd1) were identified in dilated and hypertrophic cardiomyopathies. Altered expression of MARPs is also observed in rhabdomyosarcoma, renal oncocytoma and ovarian cancer. In order to functionally characterize MARP family members CARP/Ankrd1 and Ankrd2/Arpp, we have found that both proteins interact with the tumor suppressor p53 bothin vivoandin vitroand that p53 up-regulates their expression. Our results implicate the potential role of MARPs in molecular mechanisms relevant to tumor response and progression.

Expression of cardiac ankyrin repeat protein, CARP, in malignant tumors: diagnostic use of CARP protein immunostaining in rhabdomyosarcoma

Cardiac ankyrin repeat protein (CARP) is highly expressed in cardiac muscles and detectable in normal skeletal muscles. Arpp, a close homolog of CARP, has been demonstrated to be useful for distinguishing rhabdomyosarcoma from other malignant tumors. However, the CARP distributions among malignant tumors have been poorly investigated. Here, we analyzed the comprehensive expression of CARP in malignant tumors and evaluated its potential use for rhabdomyosarcoma diagnosis. A total of 159 malignant tumors, including 34 rhabdomyosarcomas, 85 non-rhabdomyosarcomas, and 40 carcinomas, were immunohistochemically analyzed for CARP expression. Cytoplasmic expression of CARP was detected in 29 (85%) of 34 rhabdomyosarcomas. The immunoreactivity was observed in both small cells with little differentiation and differentiated tumor cells with abundant eosinophilic cytoplasm. In contrast, focal immunoreactivity for CARP was only observed in 5 (4%) of 125 non-rhabdomyosarcomas, comprising 2 malignant fibrous histiocytomas, 1 angiosarcoma, 1 epithelioid sarcoma, and 1 squamous cell carcinoma of the lung. Comparative analysis of the CARP expression profiles with those of myogenic markers in rhabdomyosarcomas revealed that myogenin (88%) and desmin (88%) exhibited the best sensitivity, followed by CARP (85%), MyoD (82%), muscle-specific actin (79%), and myoglobin (65%). MyoD (96%) and myoglobin (96%) had the best specificity, followed by CARP (95%), myogenin (95%), desmin (89%), and muscle-specific actin (86%). Our results indicate that CARP is a sensitive and specific marker for rhabdomyosarcoma and that it will be useful for the differential diagnosis of rhabdomyosarcoma.

Structural and regulatory roles of muscle ankyrin repeat protein family in skeletal muscle

The biological response of muscle to eccentric contractions (ECs) results in strengthening and protection from further injury. However, the cellular basis for this response remains unclear. Previous studies identified the muscle ankyrin repeat protein (MARP) family, consisting of cardiac ankyrin repeat protein (CARP), ankyrin repeat domain 2/ankyrin repeat protein with PEST and proline-rich region (Ankrd2/Arpp), and diabetes-associated ankyrin repeat protein (DARP), as rapidly and specifically upregulated in mice after a single bout of EC. To determine the role of these genes in skeletal muscle, a survey of skeletal muscle structural and functional characteristics was performed on mice lacking all three MARP family members (MKO). There was a slight trend toward MKO muscles having a slower fiber type distribution but no differences in muscle fiber size. Single MKO fibers were less stiff, tended to have longer resting sarcomere lengths, and expressed a longer isoform of titin than their wild-type counterparts, indicating that these proteins may play a role in the passive mechanical behavior of muscle. Finally, MKO mice showed a greater degree of torque loss after a bout of ECs compared with wild-type mice, although they recovered from the injury with the same or even improved time course. This recovery was associated with enhanced expression of the muscle regulatory genes MyoD and muscle LIM protein (MLP), suggesting that the MARP family may play both important structural and gene regulatory roles in skeletal muscle.

ARPP protein is selectively expressed in renal oncocytoma, but rarely in renal cell carcinomas

We have recently isolated a gene, Ankyrin-repeated protein with a proline-rich region (ARPP), that is highly expressed in the skeletal and cardiac muscle. Our previous immunohistochemical analysis revealed that ARPP expression was augmented in rhabdomyosarcoma but scarcely detectable in leiomyosarcoma, showing that ARPP is a useful marker for rhabdomyosarcoma. In the present study, we generated the anti-ARPP monoclonal antibody, YAS11, immunoreactive with the N-terminal region (amino-acids residues 1-145) of the ARPP protein. Further, we immunohistochemically analyzed 100 renal tumors including 14 oncocytomas, and 86 renal cell carcinomas (RCCs). We found that ARPP was highly expressed in 12 of the 14 (85.7%) oncocytomas, but was detectable in only four of the 86 (4.7%) RCCs. Interestingly, ARPP was not detected in any of 11 chromophobe RCCs, suggesting that ARPP may be useful for differential diagnosis between oncocytoma and chromophobe RCC. Furthermore, we found that ARPP was selectively expressed in part of the distal renal tubule in normal kidney. Immunoelectron microscopy with anti-ARPP antibody revealed that ARPP was localized in mitochondria and nuclei in both the normal distal renal tubule and oncocytoma, suggesting that oncocytoma may be derived from the distal nephron, and probably from part of the distal renal tubule.