Rhabdomyosarcoma (RMS) is an aggressive childhood sarcoma with two distinct subtypes, embryonal (ERMS) and alveolar (ARMS) histologies. More effective treatment is needed to improve outcomes, beyond conventional cytotoxic chemotherapy. The pan-histone deacetylase inhibitor, Suberoylanilide Hydroxamic Acid (SAHA), has shown promising efficacy in limited preclinical studies. We used a panel of human ERMS and ARMS cell lines and xenografts to evaluate the effects of SAHA as a therapeutic agent in both RMS subtypes. SAHA decreased cell viability by inhibiting S-phase progression in all cell lines tested, and induced apoptosis in all but one cell line. Molecularly, SAHA-treated cells showed activation of a DNA damage response, induction of the cell cycle inhibitors p21 Cip1 and p27 Kip1 and downregulation of Cyclin D1. In a subset of RMS cell lines, SAHA promoted features of cellular senescence and myogenic differentiation. Interestingly, SAHA treatment profoundly decreased protein levels of the driver fusion oncoprotein PAX3-FOXO1 in ARMS cells at a post-translational level. In vivo, SAHA-treated xenografts showed increased histone acetylation and induction of a DNA damage response, along with variable upregulation of p21 Cip1 and p27 Kip1. However, while the ARMS Rh41 xenograft tumor growth was significantly inhibited, there was no significant inhibition of the ERMS tumor xenograft RD. Thus, our work shows that, while SAHA is effective against ERMS and ARMS tumor cells in vitro, it has divergent in vivo effects. Together with the observed effects on the PAX3-FOXO1 fusion protein, these data suggest SAHA as a possible therapeutic agent for clinical testing in patients with fusion protein-positive RMS.

Systemic sclerosis (SSc), also known as scleroderma, is an autoimmune disorder that affects the connective tissues and has the highest mortality rate among the rheumatic diseases. One of the hallmarks of SSc is fibrosis, which may develop systemically, affecting the skin and virtually any visceral organ in the body. Fibrosis of the lungs leads to interstitial lung disease (ILD), which is currently the leading cause of death in SSc. The identification of effective treatments to stop or reverse lung fibrosis has been the main challenge in reducing SSc mortality and improving patient outcomes and quality of life. Thus, understanding the molecular mechanisms, altered pathways, and their potential interactions in SSc lung fibrosis is key to developing potential therapies. In this review, we discuss the diverse molecular mechanisms involved in SSc-related lung fibrosis to provide insights into the altered homeostasis state inherent to this fatal disease complication.

Objectives Lung fibrosis leads as the cause of death in Systemic Sclerosis (SSc), with no cure currently available. Antifibrotic Endostatin (ES) production does not reach therapeutic levels in SSc patients, suggesting a deficit in its release from Collagen-XVIII by the main cleavage enzyme, Cathepsin L (CTSL). Thus, elucidating a potential deficit in CTSL expression and activity unravels an underlying molecular cause for SSc-driven lung fibrosis. Methods Fibrosis was induced experimentally using transforming growth factor-β (TGF-β) in vivo, in primary human lung fibroblasts (pLFs), and ex-vivo, in human lung tissues. ES and CTSL expression were quantified using ELISA, RT-qPCR, immunoblotting, or immunofluorescence. Recombinant NC1-FLAG peptide was used to assess CTSL cleavage activity. CTSL expression was also compared between SSc vs normal (NL)-derived pLFs and lung tissues. Results ES levels were significantly reduced in media conditioned by TGF-β-induced pLFs. TGF-β-stimulated pLFs significantly reduced expression and secretion of CTSL into the extracellular matrix (ECM). CTSL was also sequestered in its inactive form into extracellular vesicles (EVs) further reducing its availability in the ECM. Media conditioned by TGF-β-induced pLFs showed reduced cleavage of NC1-Flag and reduced release of the antifibrotic ES fragment. SSc-derived pLFs and lung tissues expressed significantly lower levels of CTSL compared with NL. Conclusions Our findings identify CTSL as a protein protective against lung fibrosis via its activation of antifibrotic ES, and whose expression in SSc pLFs and lung tissues is suppressed. Identifying strategies to boost CTSL endogenous levels in SSc patients could serve as a viable therapeutic strategy.

With the increasing levels of atmospheric ozone depletion, there has been much concern about the causal effects of high levels of ultraviolet radiation reaching the Earth's surface on skin cancer. This has led to growing interest in identifying new active ingredients for use in commercial sunscreens. In our study, the chemical compound 2-benzoyl-3-phenylquinoxaline 1,4-dioxide (BPQ) prepared by the Beirut reaction was tested for its ability to protect a human keratinocyte cell line (HaCaT) against ultraviolet B radiation (280-315 nm). We show that BPQ exhibited strong absorbance in the UVB range, with an overall absorption spectrum very similar to that of Padimate-O, a well-known active ingredient used in commercial sunscreens. HaCaT cells, which were irradiated with UVB in the presence of multiple doses of BPQ, exhibited, in a dose-dependent fashion, a significantly higher viability and lower oxidative stress levels than cells irradiated in the absence of drug. Our results show that BPQ is a potential photoprotective drug that holds great promise for use as an active ingredient in commercial sunscreens.