Alveolar rhabdomyosarcoma: origin and prognostic implications of molecular findings

Prognostic factors of pediatric pelvic and genitourinary rhabdomyosarcoma: An analysis based on SEER database

Background

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcomas in children. This study aimed to investigate the prognostic factors of pelvic and genitourinary RMS in children and evaluate the survival outcomes of these children treated with or without radiation therapy (RT).

Methods

The Surveillance, Epidemiology, and End Results Program (SEER) database was required for children with pelvic and genitourinary RMS. Overall survival (OS) and cancer-specific survival (CSS) were analyzed using the Kaplan-Meier method, log-rank test, Cox proportional hazards models, and propensity score-matched analyses.

Results

For the 262 patients analyzed, the most common biological subtypes were embryonic (n=209, 79.8%) and alveolar (n=29, 11.1%). Patients with alveolar RMS had the worst prognosis (P < 0.05). The testis (n=122, 46.6%) was the most common location, followed by the urinary bladder (n=57, 21.8%) and prostate (n=48, 18.3%). Uterus RMS had the highest survival rate, followed by testis, urinary bladder, and prostate RMS. Favorable prognostic factors were age at diagnosis < 15 years, non-alveolar histological subtype, early tumor stage (localized/regional), specific sites (uterus and testis), and treatment (cancer-directed surgery and chemotherapy) (P < 0.05). Propensity score-matched analyses comparing the cohorts of patients treated with or without RT demonstrated no significant differences in prognostic survival (OS: P=0.872, CSS: P=0.713).

Conclusion

The nomogram constructed based on independent prognostic factors may accurately predict survival rates at 1 and 5 years. Surgery and adjuvant chemotherapy can be effective treatments, but RT fails to guarantee a survival benefit. Therefore, prospective trials evaluating RT for pediatric pelvic and genitourinary RMS are warranted.

Differential regulation of autophagy by STAU1 in alveolar rhabdomyosarcoma and non-transformed skeletal muscle cells

PURPOSE

Recent work has highlighted the therapeutic potential of targeting autophagy to modulate cell survival in a variety of diseases including cancer. Recently, we found that the RNA-binding protein Staufen1 (STAU1) is highly expressed in alveolar rhabdomyosarcoma (ARMS) and that this abnormal expression promotes tumorigenesis. Here, we asked whether STAU1 is involved in the regulation of autophagy in ARMS cells.

METHODS

We assessed the impact of STAU1 expression modulation in ARMS cell lines (RH30 and RH41), non-transformed skeletal muscle cells (C2C12) and STAU1-transgenic mice using complementary techniques.

RESULTS

We found that STAU1 silencing reduces autophagy in the ARMS cell lines RH30 and RH41, while increasing their apoptosis. Mechanistically, this inhibitory effect was found to be caused by a direct negative impact of STAU1 depletion on the stability of Beclin-1 (BECN1) and ATG16L1 mRNAs, as well as by an indirect inhibition of JNK signaling via increased expression of Dual specificity phosphatase 8 (DUSP8). Pharmacological activation of JNK or expression silencing of DUSP8 was sufficient to restore autophagy in STAU1-depleted cells. By contrast, we found that STAU1 downregulation in non-transformed skeletal muscle cells activates autophagy in a mTOR-dependent manner, without promoting apoptosis. A similar effect was observed in skeletal muscles obtained from STAU1-overexpressing transgenic mice.

CONCLUSIONS

Together, our data indicate an effect of STAU1 on autophagy regulation in ARMS cells and its differential role in non-transformed skeletal muscle cells. Our findings suggest a cancer-specific potential of targeting STAU1 for the treatment of ARMS.

Therapeutic Approaches Targeting PAX3-FOXO1 and Its Regulatory and Transcriptional Pathways in Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is a family of soft tissue cancers that are related to the skeletal muscle lineage and predominantly occur in children and young adults. A specific chromosomal translocation t(2;13)(q35;q14) that gives rise to the chimeric oncogenic transcription factor PAX3-FOXO1 has been identified as a hallmark of the aggressive alveolar subtype of RMS. PAX3-FOXO1 cooperates with additional molecular changes to promote oncogenic transformation and tumorigenesis in various human and murine models. Its expression is generally restricted to RMS tumor cells, thus providing a very specific target for therapeutic approaches for these RMS tumors. In this article, we review the recent understanding of PAX3-FOXO1 as a transcription factor in the pathogenesis of this cancer and discuss recent developments to target this oncoprotein for treatment of RMS.