New Insights on the Nuclear Functions and Targeting of FAK in Cancer

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase over-expressed and activated in both adult and pediatric cancers, where it plays important roles in the regulation of pathogenesis and progression of the malignant phenotype. FAK exerts its functions in cancer by two different ways: a kinase activity in the cytoplasm, mainly dependent on the integrin signaling, and a scaffolding activity into the nucleus by networking with different gene expression regulators. For this reason, FAK has to be considered a target with high therapeutic values. Indeed, evidence suggests that FAK targeting could be effective, either alone or in combination, with other already available treatments. Here, we propose an overview of the novel insights about FAK's structure and nuclear functions, with a special focus on the recent findings concerning the roles of this protein in cancer. Additionally, we provide a recent update on FAK inhibitors that are currently in clinical trials for patients with cancer, and discuss the challenge and future directions of drug-based anti-FAK targeted therapies

FAK Signaling in Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of children and adolescents. The fusion-positive (FP)-RMS variant expressing chimeric oncoproteins such as PAX3-FOXO1 and PAX7-FOXO1 is at high risk. The fusion negative subgroup, FN-RMS, has a good prognosis when non-metastatic. Despite a multimodal therapeutic approach, FP-RMS and metastatic FN-RMS often show a dismal prognosis with 5-year survival of less than 30%. Therefore, novel targets need to be discovered to develop therapies that halt tumor progression, reducing long-term side effects in young patients. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that regulates focal contacts at the cellular edges. It plays a role in cell motility, survival, and proliferation in response to integrin and growth factor receptors' activation. FAK is often dysregulated in cancer, being upregulated and/or overactivated in several adult and pediatric tumor types. In RMS, both in vitro and preclinical studies point to a role of FAK in tumor cell motility/invasion and proliferation, which is inhibited by FAK inhibitors. In this review, we summarize the data on FAK expression and modulation in RMS. Moreover, we give an overview of the approaches to inhibit FAK in both preclinical and clinical cancer settings

DNA Damage Response Gene Signature as Potential Treatment Markers for Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is a rapidly progressive cancer that often develops resistance against DNA damage inducers, such as radiotherapy and chemotherapy, which are still the standard of care regimens for this tumor. Thus, the identification of biomarkers capable of monitoring the clinical progression of OSCC and its responsiveness to therapy is strongly required. To meet this need, here we have employed Whole Genome Sequencing and RNA-seq data from a cohort of 316 patients retrieved from the TCGA Pan-Cancer Atlas to analyze the genomic and transcriptomic status of the DNA damage response (DDR) genes in OSCC. Then, we correlated the transcriptomic data with the clinical parameters of each patient. Finally, we relied on transcriptomic and drug sensitivity data from the CTRP v2 portal, performing Pearson's correlation analysis to identify putative vulnerabilities of OSCC cell lines correlated with DDR gene expression. Our results indicate that several DDR genes show a high frequency of genomic and transcriptomic alterations and that the expression of some of them correlates with OSCC grading and infection by the human papilloma virus. In addition, we have identified a signature of eight DDR genes (namely CCNB1, CCNB2, CDK2, CDK4, CHECK1, E2F1, FANCD2, and PRKDC) that could be predictive for OSCC response to the novel antitumor compounds sorafenib and tipifarnib-P1. Altogether, our data demonstrate that alterations in DDR genes could have an impact on the biology of OSCC. Moreover, here we propose a DDR gene signature whose expression could be predictive of OSCC responsiveness to therapy

MET Inhibition Sensitizes Rhabdomyosarcoma Cells to NOTCH Signaling Suppression

Drug resistance; Soft tissue sarcoma; Targeted therapyResistencia a las drogas; Sarcoma de tejido blando; Terapia dirigidaResistència als fàrmacs; Sarcoma dels teixits tous; Teràpia dirigidaRhabdomyosarcoma (RMS) is a pediatric myogenic soft tissue sarcoma. The Fusion-Positive (FP) subtype expresses the chimeric protein PAX3-FOXO1 (P3F) while the Fusion-Negative (FN) is devoid of any gene translocation. FP-RMS and metastatic FN-RMS are often unresponsive to conventional therapy. Therefore, novel therapeutic approaches are needed to halt tumor progression. NOTCH signaling has oncogenic functions in RMS and its pharmacologic inhibition through γ-secretase inhibitors blocks tumor growth in vitro and in vivo. Here, we show that NOTCH signaling blockade resulted in the up-regulation and phosphorylation of the MET oncogene in both RH30 (FP-RMS) and RD (FN-RMS) cell lines. Pharmacologic inhibition of either NOTCH or MET signaling slowed proliferation and restrained cell survival compared to control cells partly by increasing Annexin V and CASP3/7 activation. Co-treatment with NOTCH and MET inhibitors significantly amplified these effects and enhanced PARP1 cleavage in both cell lines. Moreover, it severely hampered cell migration, colony formation, and anchorage-independent growth compared to single-agent treatments in both cell lines and significantly prevented the growth of FN-RMS cells grown as spheroids. Collectively, our results unveil the overexpression of the MET oncogene by NOTCH signaling targeting in RMS cells and show that MET pathway blockade sensitizes them to NOTCH inhibition.This research was funded by Associazione Italiana per la Ricerca sul Cancro (AIRC) #15312 to RR and #24696 to FM; Italian Ministry of Health (Ricerca Corrente) to BDA, CQ, and RR; AIRC 5xmille #9962 to FL; Italian Ministry of Health (Fondi 5xmille 2021-2022) to RR; Alleanza Contro il Cancro (ACC) Italian Network-Working Group Sarcomas to BDA, RM, and RR; Fondi Ateneo 2019 to FM; MIUR-Italy: Grant to Department of Science, Roma Tre University (Dipartimento di Eccellenza, ARTICOLO 1, COMMI 314—337 LEGGE 232/2016) to MCe and PM

CDK9 as a Valuable Target in Cancer: From Natural Compounds Inhibitors to Current Treatment in Pediatric Soft Tissue Sarcomas

Cyclin-Dependent Kinases (CDKs) are well-known reliable targets for cancer treatment being often deregulated. Among them, since the transcription-associated CDK9 represents the sentry of cell transcriptional homeostasis, it can be a valuable target for managing cancers in which the transcriptional machinery is dysregulated by tumor-driver oncogenes. Here we give an overview of some natural compounds identified as CDK inhibitors with reported activity also against CDK9, that were taken as a model for the development of highly active synthetic anti-CDK9 agents. After, we summarize the data on CDK9 inhibition in a group of rare pediatric solid tumors such as rhabdomyosarcoma, Ewing's sarcoma, synovial sarcoma and malignant rhabdoid tumors (soft tissue sarcomas), highlighting the more recent results in this field. Finally, we discuss the perspective and challenge of CDK9 modulation in cancer

Radioresistance in rhabdomyosarcomas: Much more than a question of dose

Management of rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children, frequently accounting the genitourinary tract is complex and requires a multimodal therapy. In particular, as a consequence of the advancement in dose conformity technology, radiation therapy (RT) has now become the standard therapeutic option for patients with RMS. In the clinical practice, dose and timing of RT are adjusted on the basis of patients' risk stratification to reduce late toxicity and side effects on normal tissues. However, despite the substantial improvement in cure rates, local failure and recurrence frequently occur. In this review, we summarize the general principles of the treatment of RMS, focusing on RT, and the main molecular pathways and specific proteins involved into radioresistance in RMS tumors. Specifically, we focused on DNA damage/repair, reactive oxygen species, cancer stem cells, and epigenetic modifications that have been reported in the context of RMS neoplasia in both in vitro and in vivo studies. The precise elucidation of the radioresistance-related molecular mechanisms is of pivotal importance to set up new more effective and tolerable combined therapeutic approaches that can radiosensitize cancer cells to finally ameliorate the overall survival of patients with RMS, especially for the most aggressive subtypes

Spermine oxidase induces DNA damage and sensitizes fusion negative rhabdomyosarcoma cells to irradiation

Rhabdomyosarcoma (RMS) is a pediatric myogenic soft tissue sarcoma that includes fusion-positive (FP) and fusion-negative (FN) molecular subtypes. FP-RMS expresses PAX3-FOXO1 fusion protein and often shows dismal prognosis. FN-RMS shows cytogenetic abnormalities and frequently harbors RAS pathway mutations. Despite the multimodal heavy chemo and radiation therapeutic regimens, high risk metastatic/recurrent FN-RMS shows a 5-year survival less than 30% due to poor sensitivity to chemo-radiotherapy. Therefore, the identification of novel targets is needed. Polyamines (PAs) such as putrescine (PUT), spermidine (SPD) and spermine (SPM) are low-molecular-mass highly charged molecules whose intracellular levels are strictly modulated by specific enzymes. Among the latter, spermine oxidase (SMOX) regulates polyamine catabolism oxidizing SPM to SPD, which impacts cellular processes such as apoptosis and DNA damage response. Here we report that low SMOX levels are associated with a worse outcome in FN-RMS, but not in FP-RMS, patients. Consistently, SMOX expression is downregulated in FN-RMS cell lines as compared to normal myoblasts. Moreover, SMOX transcript levels are reduced FN-RMS cells differentiation, being indirectly downregulated by the muscle transcription factor MYOD. Noteworthy, forced expression of SMOX in two cell lines derived from high-risk FN-RMS: 1) reduces SPM and upregulates SPD levels; 2) induces G0/G1 cell cycle arrest followed by apoptosis; 3) impairs anchorage-independent and tumor spheroids growth; 4) inhibits cell migration; 5) increases γH2AX levels and foci formation indicative of DNA damage. In addition, forced expression of SMOX and irradiation synergize at activating ATM and DNA-PKCs, and at inducing γH2AX expression and foci formation, which suggests an enhancement in DNA damage response. Irradiated SMOX-overexpressing FN-RMS cells also show significant decrease in both colony formation capacity and spheroids growth with respect to single approaches. Thus, our results unveil a role for SMOX as inhibitor of tumorigenicity of FN-RMS cells in vitro. In conclusion, our in vitro results suggest that SMOX induction could be a potential combinatorial approach to sensitize FN-RMS to ionizing radiation and deserve further in-depth studies

MS-275 (Entinostat) Promotes Radio-sensitivity in PAX3-FOXO1 Rhabdomyosarcoma cells

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of childhood. About 25% of RMS expresses fusion oncoproteins such as PAX3/PAX7‐FOXO1 (fusion‐positive, FP) while fusion‐negative (FN)‐RMS harbors RAS mutations. Radiotherapy (RT) plays a crucial role in local control but metastatic RMS is often radio‐resistant. HDAC inhibitors (HDACi) radio‐sensitize different cancer cells types. Thus, we evaluated MS−275 (Entinostat), a Class I and IV HDACi, in combination with RT on RMS cells in vitro and in vivo. MS−275 reversibly hampered cell survival in vitro in FN‐RMS RD (RASmut) and irreversibly in FP‐RMS RH30 cell lines down‐regulating cyclin A, B, and D1, up‐regulating p21 and p27 and reducing ERKs activity, and c‐Myc expression in RD and PI3K/Akt/mTOR activity and N‐Myc expression in RH30 cells. Further, MS−275 and RT combination reduced colony formation ability of RH30 cells. In both cell lines, co‐treatment increased DNA damage repair inhibition and reactive oxygen species formation, down‐regulated NRF2, SOD, CAT and GPx4 anti‐oxidant genes and improved RT ability to induce G2 growth arrest. MS−275 inhibited in vivo growth of RH30 cells and completely prevented the growth of RT‐unresponsive RH30 xenografts when combined with radiation. Thus, MS−275 could be considered as a radio‐sensitizing agent for the treatment of intrinsically radio‐resistant PAX3‐FOXO1 RMS

Hyperactive Akt1 Signaling Increases Tumor Progression and DNA Repair in Embryonal Rhabdomyosarcoma RD Line and Confers Susceptibility to Glycolysis and Mevalonate Pathway Inhibitors

In pediatric rhabdomyosarcoma (RMS), elevated Akt signaling is associated with increased malignancy. Here, we report that expression of a constitutively active, myristoylated form of Akt1 (myrAkt1) in human RMS RD cells led to hyperactivation of the mammalian target of rapamycin (mTOR)/70-kDa ribosomal protein S6 kinase (p70S6K) pathway, resulting in the loss of both MyoD and myogenic capacity, and an increase of Ki67 expression due to high cell mitosis. MyrAkt1 signaling increased migratory and invasive cell traits, as detected by wound healing, zymography, and xenograft zebrafish assays, and promoted repair of DNA damage after radiotherapy and doxorubicin treatments, as revealed by nuclear detection of phosphorylated H2A histone family member X (γH2AX) through activation of DNA-dependent protein kinase (DNA-PK). Treatment with synthetic inhibitors of phosphatidylinositol-3-kinase (PI3K) and Akt was sufficient to completely revert the aggressive cell phenotype, while the mTOR inhibitor rapamycin failed to block cell dissemination. Furthermore, we found that pronounced Akt1 signaling increased the susceptibility to cell apoptosis after treatments with 2-deoxy-D-glucose (2-DG) and lovastatin, enzymatic inhibitors of hexokinase, and 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR), especially in combination with radiotherapy and doxorubicin. In conclusion, these data suggest that restriction of glucose metabolism and the mevalonate pathway, in combination with standard therapy, may increase therapy success in RMS tumors characterized by a dysregulated Akt signaling

The botanical drug PBI-05204, a supercritical CO2 extract of Nerium oleander, sensitizes alveolar and embryonal rhabdomyosarcoma to radiotherapy in vitro and in vivo

: Treatment of rhabdomyosarcoma (RMS), the most common a soft tissue sarcoma in childhood, provides intensive multimodal therapy, with radiotherapy (RT) playing a critical role for local tumor control. However, since RMS efficiently activates mechanisms of resistance to therapies, despite improvements, the prognosis remains still largely unsatisfactory, mainly in RMS expressing chimeric oncoproteins PAX3/PAX7-FOXO1, and fusion-positive (FP)-RMS. Cardiac glycosides (CGs), plant-derived steroid-like compounds with a selective inhibitory activity of the Na+/K+-ATPase pump (NKA), have shown antitumor and radio-sensitizing properties. Herein, the therapeutic properties of PBI-05204, an extract from Nerium oleander containing the CG oleandrin already studied in phase I and II clinical trials for cancer patients, were investigated, in vitro and in vivo, against FN- and FP-RMS cancer models. PBI-05204 induced growth arrest in a concentration dependent manner, with FP-RMS being more sensitive than FN-RMS, by differently regulating cell cycle regulators and commonly upregulating cell cycle inhibitors p21Waf1/Cip1 and p27Cip1/Kip1. Furthermore, PBI-05204 concomitantly induced cell death on both RMS types and senescence in FN-RMS. Notably, PBI-05204 counteracted in vitro migration and invasion abilities and suppressed the formation of spheroids enriched in CD133+ cancer stem cells (CSCs). PBI-05204 sensitized both cell types to RT by improving the ability of RT to induce G2 growth arrest and counteracting the RT-induced activation of both Non-Homologous End-Joining and homologous recombination DSBs repair pathways. Finally, the antitumor and radio-sensitizing proprieties of PBI-05204 were confirmed in vivo. Notably, both in vitro and in vivo evidence confirmed the higher sensitivity to PBI-05204 of FP-RMS. Thus, PBI-05204 represents a valid radio-sensitizing agent for the treatment of RMS, including the intrinsically radio-resistant FP-RMS