Small molecules, LLL12 and FLLL32, inhibit STAT3 and exhibit potent growth suppressive activity in osteosarcoma cells and tumor growth in mice.

Constitutive activation of Signal Transducers and Activators of Transcription 3 (STAT3) is frequently detected in osteosarcoma, and hence, may serve as a therapeutic target. In order to target STAT3, we tested two new STAT3 inhibitors, LLL12 and FLLL32. LLL12 and FLLL32 inhibit STAT3 phosphorylation and STAT3 downstream targets. LLL12 and FLLL32 also inhibit IL-6 induced STAT3 phosphorylation. The inhibition of STAT3 by LLL12 and FLLL32 resulted in the induction of apoptosis, reduction of plating efficiency, and migration in osteosarcoma cells. Furthermore, LLL12 and FLLL32 inhibited SJSA osteosarcoma cells and OS-33 tumor growth in murine xenografts. These results provide evidence that constitutive STAT3 signaling is required for osteosarcoma survival and migration in vitro and tumor growth in vivo. Blocking persistent STAT3 signaling by LLL12 and FLLL32 may be a novel therapeutic approach for osteosarcoma.

Characterizing Out-of-Pocket Payments and Financial Assistance for Patients Prescribed Abiraterone and Enzalutamide at an Academic Cancer Center Specialty Pharmacy.

PURPOSE: Abiraterone and enzalutamide are commonly used oral cancer therapies for patients with prostate cancer, both with potentially high out-of-pocket costs for patients. We investigated the prevalence of financial assistance mechanisms used to alleviate out-of-pocket costs and the association of these mechanisms with timing of treatment initiation of abiraterone or enzalutamide. METHODS: Using data from the medical center's specialty pharmacy, we identified first prescriptions for abiraterone or enzalutamide between January 1, 2017, and March 31, 2019. Prescriptions dispensed at an external pharmacy or that were discontinued for reasons unrelated to cost were excluded. Patient demographics, insurance coverage, out-of-pocket cost, and number of days between prescribed date and pill-to-mouth date were collected. RESULTS: Among 220 prescriptions in our final cohort, 185 were filled through our internal specialty pharmacy, 23 through a manufacturer-sponsored patient assistance program (PAP), and 12 were never filled because of cost. One third of the prescriptions in our final cohort (n = 66) were filled with financial assistance: PAP (10%), copay cards (9%), and grants (11%). The median amount of assistance received for the first fill was $2,860 US dollars (USD) (interquartile range $1,856-$10,717 USD). Prescriptions with an out-of-pocket cost < $100 USD were filled in the shortest time (median 5 days), whereas those filled through a PAP had the longest time to initiation (median 30.5 days). CONCLUSION: Among patients prescribed oral therapies for prostate cancer at a single institution, one third of patients received financial assistance. Although receiving assistance is likely to improve financial toxicity, waiting for assistance may lead to longer time to initiation of medication.

The novel curcumin analog FLLL32 decreases STAT3 DNA binding activity and expression, and induces apoptosis in osteosarcoma cell lines.

BACKGROUND: Curcumin is a naturally occurring phenolic compound shown to have a wide variety of antitumor activities; however, it does not attain sufficient blood levels to do so when ingested. Using structure-based design, a novel compound, FLLL32, was generated from curcumin. FLLL32 possesses superior biochemical properties and more specifically targets STAT3, a transcription factor important in tumor cell survival, proliferation, metastasis, and chemotherapy resistance. In our previous work, we found that several canine and human osteosarcoma (OSA) cell lines, but not normal osteoblasts, exhibit constitutive phosphorylation of STAT3. Compared to curcumin, we hypothesized that FLLL32 would be more efficient at inhibiting STAT3 function in OSA cells and that this would result in enhanced downregulation of STAT3 transcriptional targets and subsequent death of OSA cells. METHODS: Human and canine OSA cells were treated with vehicle, curcumin, or FLLL32 and the effects on proliferation (CyQUANT®), apoptosis (SensoLyte® Homogeneous AMC Caspase- 3/7 Assay kit, western blotting), STAT3 DNA binding (EMSA), and vascular endothelial growth factor (VEGF), survivin, and matrix metalloproteinase-2 (MMP2) expression (RT-PCR, western blotting) were measured. STAT3 expression was measured by RT-PCR, qRT- PCR, and western blotting. RESULTS: Our data showed that FLLL32 decreased STAT3 DNA binding by EMSA. FLLL32 promoted loss of cell proliferation at lower concentrations than curcumin leading to caspase-3- dependent apoptosis, as evidenced by PARP cleavage and increased caspase 3/7 activity; this could be inhibited by treatment with the pan-caspase inhibitor Z-VAD-FMK. Treatment of OSA cells with FLLL32 decreased expression of survivin, VEGF, and MMP2 at both mRNA and protein levels with concurrent decreases in phosphorylated and total STAT3; this loss of total STAT3 occurred, in part, via the ubiquitin-proteasome pathway. CONCLUSIONS: These data demonstrate that the novel curcumin analog FLLL32 has biologic activity against OSA cell lines through inhibition of STAT3 function and expression. Future work with FLLL32 will define the therapeutic potential of this compound in vivo.

LRP1B mutations are associated with favorable outcomes to immune checkpoint inhibitors across multiple cancer types.

BACKGROUND: Low-density lipoprotein receptor-related protein 1b (encoded by LRP1B) is a putative tumor suppressor, and preliminary evidence suggests LRP1B-mutated cancers may have improved outcomes with immune checkpoint inhibitors (ICI). METHODS: We conducted a multicenter, retrospective pan-cancer analysis of patients with LRP1B alterations treated with ICI at Duke University, Johns Hopkins University (JHU) and University of Michigan (UM). The primary objective was to assess the association between overall response rate (ORR) to ICI and pathogenic or likely pathogenic (P/LP) LRP1B alterations compared with LRP1B variants of unknown significance (VUS). Secondary outcomes were the associations with progression-free survival (PFS) and overall survival (OS) by LRP1B status. RESULTS: We identified 101 patients (44 Duke, 35 JHU, 22 UM) with LRP1B alterations who were treated with ICI. The most common tumor types by alteration (P/LP vs VUS%) were lung (36% vs 49%), prostate (9% vs 7%), sarcoma (5% vs 7%), melanoma (9% vs 0%) and breast cancer (3% vs 7%). The ORR for patients with LRP1B P/LP versus VUS alterations was 54% and 13%, respectively (OR 7.5, 95% CI 2.9 to 22.3, p=0.0009). P/LP LRP1B alterations were associated with longer PFS (HR 0.42, 95% CI 0.26 to 0.68, p=0.0003) and OS (HR 0.62, 95% CI 0.39 to 1.01, p=0.053). These results remained consistent when excluding patients harboring microsatellite instability (MSI) and controlling for tumor mutational burden (TMB). CONCLUSIONS: This multicenter study shows significantly better outcomes with ICI therapy in patients harboring P/LP versus VUS LRP1B alterations, independently of TMB/MSI status. Further mechanistic and prospective validation studies are warranted.

A novel small molecule inhibits STAT3 phosphorylation and DNA binding activity and exhibits potent growth suppressive activity in human cancer cells.

BACKGROUND: Targeting Signal Transducer and Activator of Transcription 3 (STAT3) signaling is an attractive therapeutic approach for most types of human cancers with constitutively activated STAT3. A novel small molecular STAT3 inhibitor, FLLL32 was specifically designed from dietary agent, curcumin to inhibit constitutive STAT3 signaling in multiple myeloma, glioblastoma, liver cancer, and colorectal cancer cells. RESULTS: FLLL32 was found to be a potent inhibitor of STAT3 phosphorylation, STAT3 DNA binding activity, and the expression of STAT3 downstream target genes in vitro, leading to the inhibition of cell proliferation as well as the induction of Caspase-3 and PARP cleavages in human multiple myeloma, glioblastoma, liver cancer, and colorectal cancer cell lines. However, FLLL32 exhibited little inhibition on some tyrosine kinases containing SH2 or both SH2 and SH3 domains, and other protein and lipid kinases using a kinase profile assay. FLLL32 was also more potent than four previously reported JAK2 and STAT3 inhibitors as well as curcumin to inhibit cell viability in these cancer cells. Furthermore, FLLL32 selectively inhibited the induction of STAT3 phosphorylation by Interleukin-6 but not STAT1 phosphorylation by IFN-γ. CONCLUSION: Our findings indicate that FLLL32 exhibits potent inhibitory activity to STAT3 and has potential for targeting multiple myeloma, glioblastoma, liver cancer, and colorectal cancer cells expressing constitutive STAT3 signaling.

The small molecule curcumin analog FLLL32 induces apoptosis in melanoma cells via STAT3 inhibition and retains the cellular response to cytokines with anti-tumor activity.

BACKGROUND: We characterized the biologic effects of a novel small molecule STAT3 pathway inhibitor that is derived from the natural product curcumin. We hypothesized this lead compound would specifically inhibit the STAT3 signaling pathway to induce apoptosis in melanoma cells. RESULTS: FLLL32 specifically reduced STAT3 phosphorylation at Tyr705 (pSTAT3) and induced apoptosis at micromolar amounts in human melanoma cell lines and primary melanoma cultures as determined by annexin V/propidium iodide staining and immunoblot analysis. FLLL32 treatment reduced expression of STAT3-target genes, induced caspase-dependent apoptosis, and reduced mitochondrial membrane potential. FLLL32 displayed specificity for STAT3 over other homologous STAT proteins. In contrast to other STAT3 pathway inhibitors (WP1066, JSI-124, Stattic), FLLL32 did not abrogate IFN-gamma-induced pSTAT1 or downstream STAT1-mediated gene expression as determined by Real Time PCR. In addition, FLLL32 did not adversely affect the function or viability of immune cells from normal donors. In peripheral blood mononuclear cells (PBMCs), FLLL32 inhibited IL-6-induced pSTAT3 but did not reduce signaling in response to immunostimulatory cytokines (IFN-gamma, IL 2). Treatment of PBMCs or natural killer (NK) cells with FLLL32 also did not decrease viability or granzyme b and IFN-gamma production when cultured with K562 targets as compared to vehicle (DMSO). CONCLUSIONS: These data suggest that FLLL32 represents a lead compound that could serve as a platform for further optimization to develop improved STAT3 specific inhibitors for melanoma therapy.

Insertional Mutagenesis Identifies a STAT3/Arid1b/ß-catenin Pathway Driving Neurofibroma Initiation.

To identify genes and signaling pathways that initiate Neurofibromatosis type 1 (NF1) neurofibromas, we used unbiased insertional mutagenesis screening, mouse models, and molecular analyses. We mapped an Nf1-Stat3-Arid1b/ß-catenin pathway that becomes active in the context of Nf1 loss. Genetic deletion of Stat3 in Schwann cell progenitors (SCPs) and Schwann cells (SCs) prevents neurofibroma formation, decreasing SCP self-renewal and ß-catenin activity. ß-catenin expression rescues effects of Stat3 loss in SCPs. Importantly, P-STAT3 and ß-catenin expression correlate in human neurofibromas. Mechanistically, P-Stat3 represses Gsk3ß and the SWI/SNF gene Arid1b to increase ß-catenin. Knockdown of Arid1b or Gsk3ß in Stat3(fl/fl);Nf1(fl/fl);DhhCre SCPs rescues neurofibroma formation after in vivo transplantation. Stat3 represses Arid1b through histone modification in a Brg1-dependent manner, indicating that epigenetic modification plays a role in early tumorigenesis. Our data map a neural tumorigenesis pathway and support testing JAK/STAT and Wnt/ß-catenin pathway inhibitors in neurofibroma therapeutic trials.

Inhibition of the JAK2/STAT3 signaling pathway exerts a therapeutic effect on osteosarcoma.

Osteosarcoma (OS) is the most common type of malignant bone tumor. Despite aggressive multimodal treatments, including surgical resection, chemotherapy and adjunctive immunotherapies, patients with OS with high-grade malignancy have a poor five-year survival rate that has remained unchanged over the past two decades, highlighting the urgent requirement for novel therapeutic approaches. Signal transducers and activators of transcription 3 (STAT3) has been implicated as an oncogene and therapeutic target in a variety of neoplastic diseases. The aim of the present study was to determine whether inhibition of the janus kinase 2 (JAK2)/STAT3 pathway by FLLL32, a specific JAK2/STAT3 inhibitor, is able to provide a potential therapy for OS. FLLL32 inhibited OS cell growth in vitro and delayed OS growth in an OS xenograft nude mouse model. STAT3 knockdown by short hairpin RNA delayed OS formation in vivo. Thus, the JAK2/STAT3 pathway is important in OS formation. Efficacy of the FLLL32 pharmacological inhibitor in delaying OS growth suggests that targeting JAK2/STAT3 may be a potential therapeutic strategy for patients with OS.

Structurally modified curcumin analogs inhibit STAT3 phosphorylation and promote apoptosis of human renal cell carcinoma and melanoma cell lines.

The Janus kinase-2 (Jak2)-signal transducer and activator of transcription-3 (STAT3) pathway is critical for promoting an oncogenic and metastatic phenotype in several types of cancer including renal cell carcinoma (RCC) and melanoma. This study describes two small molecule inhibitors of the Jak2-STAT3 pathway, FLLL32 and its more soluble analog, FLLL62. These compounds are structurally distinct curcumin analogs that bind selectively to the SH2 domain of STAT3 to inhibit its phosphorylation and dimerization. We hypothesized that FLLL32 and FLLL62 would induce apoptosis in RCC and melanoma cells and display specificity for the Jak2-STAT3 pathway. FLLL32 and FLLL62 could inhibit STAT3 dimerization in vitro. These compounds reduced basal STAT3 phosphorylation (pSTAT3), and induced apoptosis in four separate human RCC cell lines and in human melanoma cell lines as determined by Annexin V/PI staining. Apoptosis was also confirmed by immunoblot analysis of caspase-3 processing and PARP cleavage. Pre-treatment of RCC and melanoma cell lines with FLLL32/62 did not inhibit IFN-γ-induced pSTAT1. In contrast to FLLL32, curcumin and FLLL62 reduced downstream STAT1-mediated gene expression of IRF1 as determined by Real Time PCR. FLLL32 and FLLL62 significantly reduced secretion of VEGF from RCC cell lines in a dose-dependent manner as determined by ELISA. Finally, each of these compounds inhibited in vitro generation of myeloid-derived suppressor cells. These data support further investigation of FLLL32 and FLLL62 as lead compounds for STAT3 inhibition in RCC and melanoma.

A liquid chromatography-tandem mass spectrometric method for quantification of curcuminoids in cell medium and mouse plasma.

Curcumin and tetrahydrocurcumin (THC) have been found as potent DNMT1 inhibitors, but they suffer from low oral bioavailability and rapid metabolism in vivo. To circumvent these problems, two curcumin analogs: 1,7-bis(3,4-dimethoxyphenyl)-4,4-dimethyl-1,6-heptadiene-3,5-dione (TMC) and 1,7-bis(3,4-dimethoxyphenyl)-4-cyclohexyl-1,6-heptadiene-3,5-dione (DMCHC) have been synthesized to enhance their stability by blocking the two metabolic sites, the phenolic and C4 methylene moieties. Both compounds have shown inhibitory activity on M. SssI similar to that of curcumin and THC (Poster, M1114, AAPS, 2009). Preclinical pharmacokinetics has yet to be performed. In this paper, a simple liquid chromatography-tandem mass spectrometric method was developed for the determination of these four curcuminoids in cell medium and mouse plasma. The method showed linearity from 1 to 1000 ng/mL with the lower limit of quantification of 1 ng/mL in cell medium, and 5 ng/mL in mouse plasma for all test curcuminoids. The within-day coefficients of variation were found to be below 15% and the accuracy was in the range of 85-115%. This method was subsequently used to evaluate their stability in these matrices and a pilot pharmacokinetics of curcumin, DMCHC and TMC in mice after an intraperitoneal (i.p.) cassette dosing of 10mg/kg each. Curcuminoids degraded in two phases with terminal half lives of 186, 813, 724, and 2000 min for curcumin, THC, TMC, and DMCHC, respectively, in cell culture medium. In plasma, their respective half lives were 111, 232, 1202 and 3000 min. These data demonstrated that their stability is in the order curcumin