Patient-derived tumor xenograft study with CDK4/6 inhibitor plus AKT inhibitor for the management of metastatic castration-resistant prostate cancer.

Metastatic castration-resistant prostate cancer (mCRPC) is an aggressive malignancy with poor outcomes. To investigate novel therapeutic strategies, we characterized three new metastatic prostate cancer PDTX models and developed 3D spheroids from each to investigate molecular targeted therapy combinations including CDK4/6 inhibitors (CDK4/6i) with AKT inhibitors (ATKi). Metastatic prostate cancer tissue was collected and three PDTX models were established and characterized using WES. PDTX 3-D spheroids were developed from these three PDTXs to show resistance patterns and test novel molecular targeted therapies. CDK4/6i's were combined with AKTi's to assess synergistic antitumor response to prove our hypothesis that blockade of AKT overcomes drug resistance to CDK4/6 inhibitor. This combination was evaluated in PDTX 3-D spheroids and in vivo experiments with responses measured by tumor volumes, PSA and Ga-68 PSMA-11 PET-CT imaging. We demonstrated CDK4/6i's with AKTi's possess synergistic antitumor activity in three mCRPC PDTX models. These models have multiple unique pathogenic and deleterious genomic alterations with resistance to single agent CDK4/6i's. Despite this, combination therapy with AKTi's was able to overcome resistance mechanisms. The IHC and Western blot analysis confirmed on target effects, while tumor volume, serum PSA ELISA, and radionuclide imaging demonstrated response to therapy with statistically significant SUV differences seen with Ga-68 PSMA-11 PET-CT. These preclinical data demonstrating antitumor synergy by overcoming single agent CDK 4/6i as well as AKTi drug resistance provide the rational for a clinical trial combining a CDK4/6i with an AKTi in mCRPC patients whose tumor expresses wild type RB1.

The genomic and evolutionary landscapes of anaplastic thyroid carcinoma.

Anaplastic thyroid carcinoma is arguably the most lethal human malignancy. It often co-occurs with differentiated thyroid cancers, yet the molecular origins of its aggressivity are unknown. We sequenced tumor DNA from 329 regions of thyroid cancer, including 213 from patients with primary anaplastic thyroid carcinomas. We also whole genome sequenced 9 patients using multi-region sequencing of both differentiated and anaplastic thyroid cancer components. Using these data, we demonstrate thatanaplastic thyroid carcinomas have a higher burden of mutations than other thyroid cancers, with distinct mutational signatures and molecular subtypes. Further, different cancer driver genes are mutated in anaplastic and differentiated thyroid carcinomas, even those arising in a single patient. Finally, we unambiguously demonstrate that anaplastic thyroid carcinomas share a genomic origin with co-occurring differentiated carcinomas and emerge from a common malignant field through acquisition of characteristic clonal driver mutations.

CRISPR screening identifies BET and mTOR inhibitor synergy in cholangiocarcinoma through serine glycine one carbon.

Patients with cholangiocarcinoma have poor clinical outcomes due to late diagnoses, poor prognoses, and limited treatment strategies. To identify drug combinations for this disease, we have conducted a genome-wide CRISPR screen anchored on the bromodomain and extraterminal domain (BET) PROTAC degrader ARV825, from which we identified anticancer synergy when combined with genetic ablation of members of the mTOR pathway. This combination effect was validated using multiple pharmacological BET and mTOR inhibitors, accompanied by increased levels of apoptosis and cell cycle arrest. In a xenograft model, combined BET degradation and mTOR inhibition induced tumor regression. Mechanistically, the 2 inhibitor classes converged on H3K27ac-marked epigenetic suppression of the serine glycine one carbon (SGOC) metabolism pathway, including the key enzymes PHGDH and PSAT1. Knockdown of PSAT1 was sufficient to replicate synergy with single-agent inhibition of either BET or mTOR. Our results tie together epigenetic regulation, metabolism, and apoptosis induction as key therapeutic targets for further exploration in this underserved disease.

Thyroid-stimulating hormone receptor (TSHR) as a target for imaging differentiated thyroid cancer.

BACKGROUND: Of the half a million cases of thyroid cancer diagnosed annually, 95% are differentiated thyroid cancers. Although clinical guidelines recommend surgical resection followed by radioactive iodine ablation, loss of sodium-iodine symporter expression causes up to 20% of differentiated thyroid cancers to become radioactive iodine refractory. For patients with radioactive iodine refractory disease, there is an urgent need for new diagnostic and therapeutic approaches. We evaluated the thyroid-stimulating hormone receptor as a potential target for imaging of differentiated thyroid cancer. METHODS: We immunostained tissue microarrays containing 52 Hurthle cell carcinomas to confirm thyroid-stimulating hormone receptor expression. We radiolabeled chelator deferoxamine conjugated to recombinant human thyroid-stimulating hormone analog superagonist TR1402 with 89Zr (t1/2 = 78.4 h, ß+ =22.7%) to produce [89Zr]Zr-TR1402. We performed in vitro uptake assays in high-thyroid-stimulating hormone receptor and low-thyroid-stimulating hormone receptor-expressing THJ529T and FTC133 thyroid cancer cell lines. We performed in vivo positron emission tomography/computed tomography and biodistribution studies in male athymic nude mice bearing thyroid-stimulating hormone receptor-positive THJ529T tumors. RESULTS: Immunohistochemical analysis revealed 62% of patients (27 primary and 5 recurrent) were thyroid-stimulating hormone receptor membranous immunostain positive. In vitro uptake of 1nM [89Zr]Zr-TR1402 was 38 ± 17% bound/mg in thyroid-stimulating hormone receptor-positive THJ529T thyroid cancer cell lines compared to 3.2 ± 0.5 in the low-expressing cell line (P < .01), with a similar difference seen in FTC133 cell lines (P < .0001). In vivo and biodistribution studies showed uptake of [89Zr]Zr-TR1402 in thyroid-stimulating hormone receptor-expressing tumors, with a mean percentage of injected dose/g of 1.9 ± 0.4 at 3 days post-injection. CONCLUSION: Our observation of thyroid-stimulating hormone receptor expression in tissue microarrays and [89Zr]Zr-TR1402 accumulation in thyroid-stimulating hormone receptor-positive thyroid cancer cells and tumors suggests thyroid-stimulating hormone receptor is a promising target for imaging of differentiated thyroid cancer.

CDK4 phosphorylation status and rational use for combining CDK4/6 and BRAF/MEK inhibition in advanced thyroid carcinomas.

Background: CDK4/6 inhibitors (CDK4/6i) have been established as standard treatment against advanced Estrogen Receptor-positive breast cancers. These drugs are being tested against several cancers, including in combinations with other therapies. We identified the T172-phosphorylation of CDK4 as the step determining its activity, retinoblastoma protein (RB) inactivation, cell cycle commitment and sensitivity to CDK4/6i. Poorly differentiated (PDTC) and anaplastic (ATC) thyroid carcinomas, the latter considered one of the most lethal human malignancies, represent major clinical challenges. Several molecular evidence suggest that CDK4/6i could be considered for treating these advanced thyroid cancers. Methods: We analyzed by two-dimensional gel electrophoresis the CDK4 modification profile and the presence of T172-phosphorylated CDK4 in a collection of 98 fresh-frozen tissues and in 21 cell lines. A sub-cohort of samples was characterized by RNA sequencing and immunohistochemistry. Sensitivity to CDK4/6i (palbociclib and abemaciclib) was assessed by BrdU incorporation/viability assays. Treatment of cell lines with CDK4/6i and combination with BRAF/MEK inhibitors (dabrafenib/trametinib) was comprehensively evaluated by western blot, characterization of immunoprecipitated CDK4 and CDK2 complexes and clonogenic assays. Results: CDK4 phosphorylation was detected in all well-differentiated thyroid carcinomas (n=29), 19/20 PDTC, 16/23 ATC and 18/21 thyroid cancer cell lines, including 11 ATC-derived ones. Tumors and cell lines without phosphorylated CDK4 presented very high p16CDKN2A levels, which were associated with proliferative activity. Absence of CDK4 phosphorylation in cell lines was associated with CDK4/6i insensitivity. RB1 defects (the primary cause of intrinsic CDK4/6i resistance) were not found in 5/7 tumors without detectable phosphorylated CDK4. A previously developed 11-gene expression signature identified the likely unresponsive tumors, lacking CDK4 phosphorylation. In cell lines, palbociclib synergized with dabrafenib/trametinib by completely and permanently arresting proliferation. These combinations prevented resistance mechanisms induced by palbociclib, most notably Cyclin E1-CDK2 activation and a paradoxical stabilization of phosphorylated CDK4 complexes. Conclusion: Our study supports further clinical evaluation of CDK4/6i and their combination with anti-BRAF/MEK therapies as a novel effective treatment against advanced thyroid tumors. Moreover, the complementary use of our 11 genes predictor with p16/KI67 evaluation could represent a prompt tool for recognizing the intrinsically CDK4/6i insensitive patients, who are potentially better candidates to immediate chemotherapy.

The Bivalent Bromodomain Inhibitor MT-1 Inhibits Prostate Cancer Growth.

Bromodomains (BD) are epigenetic readers of histone acetylation involved in chromatin remodeling and transcriptional regulation of several genes including protooncogene cellular myelocytomatosis (c-Myc). c-Myc is difficult to target directly by agents due to its disordered alpha helical protein structure and predominant nuclear localization. The epigenetic targeting of c-Myc by BD inhibitors is an attractive therapeutic strategy for prostate cancer (PC) associated with increased c-Myc upregulation with advancing disease. MT-1 is a bivalent BD inhibitor that is 100-fold more potent than the first-in-class BD inhibitor JQ1. MT-1 decreased cell viability and causes cell cycle arrest in G0/G1 phase in castration-sensitive and resistant PC cell lines in a dose-dependent fashion. The inhibition of c-Myc function by MT-1 was molecularly corroborated by the de-repression of Protein Kinase D1 (PrKD) and increased phosphorylation of PrKD substrate proteins: threonine 120, serine 11, and serine 216 amino acid residues in ß-Catenin, snail, and cell division cycle 25c (CDC25c) proteins, respectively. The treatment of 3D cell cultures derived from three unique clinically annotated heavily pretreated patient-derived PC xenografts (PDX) mice models with increasing doses of MT-1 demonstrated the lowest IC50 in tumors with c-Myc amplification and clinically resistant to Docetaxel, Cabazitaxel, Abiraterone, and Enzalutamide. An intraperitoneal injection of either MT-1 or in combination with 3jc48-3, an inhibitor of obligate heterodimerization with MYC-associated protein X (MAX), in mice implanted with orthotopic PC PDX, decreased tumor growth. This is the first pre-clinical study demonstrating potential utility of MT-1 in the treatment of PC with c-Myc dysregulation.

Radiosynthesis and Preliminary Evaluation of [11C]SSI-4 for the Positron Emission Tomography Imaging of Stearoyl CoA Desaturase 1.

Stearoyl CoA desaturase 1 (SCD1) is the rate-limiting enzyme for converting saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs) and plays a key role in endogenous (de novo) fatty acid metabolism. Given that this pathway is broadly upregulated across many tumor types with an aggressive phenotype, SCD1 has emerged as a compelling target for cancer imaging and therapy. The ligand 2-(4-(2-chlorophenoxy)piperidine-1-carboxamido)-N-methylisonicotinamide (SSI-4) was identified as a potent and highly specific SCD1 inhibitor with a strong binding affinity for SCD1 at our laboratory. We herein report the radiosynthesis of [11C]SSI-4 and the preliminary biological evaluation including in vivo PET imaging of SCD1 in a human tumor xenograft model. Radiotracer [11C]SSI-4 was labeled at the carbamide position via the direct [11C]CO2 fixation on the Synthra MeIplus module in high molar activity and good radiochemical yield. In vitro cell uptake assays were performed with three hepatocellular carcinoma (HCC) cell lines and three renal cell carcinoma (RCC) cell lines. Additionally, in vivo small animal PET/CT imaging with [11C]SSI-4 and the biodistribution were carried out in a mouse model bearing HCC xenografts. Radiotracer [11C]SSI-4 afforded a 4.14 ± 0.44% (decay uncorrected, n = 10) radiochemical yield based on starting [11]CO2 radioactivity. The [11C]SSI-4 radiosynthesis time including HPLC purification and SPE formulation was 25 min from the end of bombardment to the end of synthesis (EOS). The radiochemical purity of [11C]SSI-4 was 98.45 ± 1.43% (n = 10) with a molar activity of 225.82 ± 33.54 GBq/µmol (6.10 ± 0.91 Ci/µmol) at the EOS. In vitro cell uptake study indicated all SSI-4 responsive HCC and RCC cell line uptakes demonstrate specific uptake and are blocked by standard compound SSI-4. Preliminary small animal PET/CT imaging study showed high specific uptake and block of [11C]SSI-4 uptake with co-injection of cold SSI-4 in high SCD1-expressing organs including lacrimal gland, brown fat, liver, and tumor. In summary, novel radiotracer [11C]SSI-4 was rapidly and automatedly radiosynthesized by direct [11C]CO2 fixation. Our preliminary biological evaluation results suggest [11C]SSI-4 could be a promising radiotracer for PET imaging of SCD1 overexpressing tumor tissues.

ADAR1-mediated RNA editing of SCD1 drives drug resistance and self-renewal in gastric cancer.

Targetable drivers governing 5-fluorouracil and cisplatin (5FU + CDDP) resistance remain elusive due to the paucity of physiologically and therapeutically relevant models. Here, we establish 5FU + CDDP resistant intestinal subtype GC patient-derived organoid lines. JAK/STAT signaling and its downstream, adenosine deaminases acting on RNA 1 (ADAR1), are shown to be concomitantly upregulated in the resistant lines. ADAR1 confers chemoresistance and self-renewal in an RNA editing-dependent manner. WES coupled with RNA-seq identify enrichment of hyper-edited lipid metabolism genes in the resistant lines. Mechanistically, ADAR1-mediated A-to-I editing on 3'UTR of stearoyl-CoA desaturase (SCD1) increases binding of KH domain-containing, RNA-binding, signal transduction-associated 1 (KHDRBS1), thereby augmenting SCD1 mRNA stability. Consequently, SCD1 facilitates lipid droplet formation to alleviate chemotherapy-induced ER stress and enhances self-renewal through increasing ß-catenin expression. Pharmacological inhibition of SCD1 abrogates chemoresistance and tumor-initiating cell frequency. Clinically, high proteomic level of ADAR1 and SCD1, or high SCD1 editing/ADAR1 mRNA signature score predicts a worse prognosis. Together, we unveil a potential target to circumvent chemoresistance.

Lisaftoclax (APG-2575) Is a Novel BCL-2 Inhibitor with Robust Antitumor Activity in Preclinical Models of Hematologic Malignancy.

PURPOSE: Development of B-cell lymphoma 2 (BCL-2)-specific inhibitors poses unique challenges in drug design because of BCL-2 homology domain 3 (BH3) shared homology between BCL-2 family members and the shallow surface of their protein-protein interactions. We report herein discovery and extensive preclinical investigation of lisaftoclax (APG-2575). EXPERIMENTAL DESIGN: Computational modeling was used to design "lead" compounds. Biochemical binding, mitochondrial BH3 profiling, and cell-based viability or apoptosis assays were used to determine the selectivity and potency of BCL-2 inhibitor lisaftoclax. The antitumor effects of lisaftoclax were also evaluated in several xenograft models. RESULTS: Lisaftoclax selectively binds BCL-2 (Ki < 0.1 nmol/L), disrupts BCL-2:BIM complexes, and compromises mitochondrial outer membrane potential, culminating in BAX/BAK-dependent, caspase-mediated apoptosis. Lisaftoclax exerted strong antitumor activity in hematologic cancer cell lines and tumor cells from patients with chronic lymphocytic leukemia, multiple myeloma, or Waldenström macroglobulinemia. After lisaftoclax treatment, prodeath proteins BCL-2‒like protein 11 (BIM) and Noxa increased, and BIM translocated from cytosol to mitochondria. Consistent with these apoptotic activities, lisaftoclax entered malignant cells rapidly, reached plateau in 2 hours, and significantly downregulated mitochondrial respiratory function and ATP production. Furthermore, lisaftoclax inhibited tumor growth in xenograft models, correlating with caspase activation, poly (ADP-ribose) polymerase 1 cleavage, and pharmacokinetics of the compound. Lisaftoclax combined with rituximab or bendamustine/rituximab enhanced antitumor activity in vivo. CONCLUSIONS: These findings demonstrate that lisaftoclax is a novel, orally bioavailable BH3 mimetic BCL-2-selective inhibitor with considerable potential for the treatment of certain hematologic malignancies.

Complete response in Patients With Lung-Only Metastatic Prostate Cancer: Outcome Analysis.

Lung-only metastatic prostate cancer can be seen in 4.6% of patients and historically patients with visceral metastastic disease are considered high risk. In order to determine survival outcomes in this patient population, we conducted a restrospective review of patients with metastatic hormone sensitive prostate cancer with lung-only metastases. In this single institution review, 10 patients were identified with 8 achieving a complete response and 2 achieving a partial response when treated with androgen deprevation therapy (ADT) with or without metastastetomy. The median progression free survival was 64.4 months with 8 of these patients (80%) with ongoing complete response at time of follow-up. Lung-only metastases may serve as a good prognostic characteristic which will allow the clinician to treat with ADT alone with or without surgery to minimize treatment realted toxicity and still offer the ability to achieve a complete response with prolonged survival.

Targeting BCAT1 Combined with α-Ketoglutarate Triggers Metabolic Synthetic Lethality in Glioblastoma.

Branched-chain amino acid transaminase 1 (BCAT1) is upregulated selectively in human isocitrate dehydrogenase (IDH) wildtype (WT) but not mutant glioblastoma multiforme (GBM) and promotes IDHWT GBM growth. Through a metabolic synthetic lethal screen, we report here that α-ketoglutarate (AKG) kills IDHWT GBM cells when BCAT1 protein is lost, which is reversed by reexpression of BCAT1 or supplementation with branched-chain α-ketoacids (BCKA), downstream metabolic products of BCAT1. In patient-derived IDHWT GBM tumors in vitro and in vivo, cotreatment of BCAT1 inhibitor gabapentin and AKG resulted in synthetic lethality. However, AKG failed to evoke a synthetic lethal effect with loss of BCAT2, BCKDHA, or GPT2 in IDHWT GBM cells. Mechanistically, loss of BCAT1 increased the NAD+/NADH ratio but impaired oxidative phosphorylation, mTORC1 activity, and nucleotide biosynthesis. These metabolic alterations were synergistically augmented by AKG treatment, thereby causing mitochondrial dysfunction and depletion of cellular building blocks, including ATP, nucleotides, and proteins. Partial restoration of ATP, nucleotides, proteins, and mTORC1 activity by BCKA supplementation prevented IDHWT GBM cell death conferred by the combination of BCAT1 loss and AKG. These findings define a targetable metabolic vulnerability in the most common subset of GBM that is currently incurable. SIGNIFICANCE: Metabolic synthetic lethal screening in IDHWT glioblastoma defines a vulnerability to ΑΚG following BCAT1 loss, uncovering a therapeutic strategy to improve glioblastoma treatment. See related commentary by Meurs and Nagrath, p. 2354.

YM155 Induces DNA Damage and Cell Death in Anaplastic Thyroid Cancer Cells by Inhibiting DNA Topoisomerase IIα at the ATP-Binding Site.

Anaplastic thyroid cancer (ATC) is among the most aggressive of human cancers, and currently there are few effective treatments for most patients. YM155, first identified as a survivin inhibitor, was highlighted in a high-throughput screen performed by the National Cancer Institute, killing ATC cells in vitro and in vivo. However, there was no association between survivin expression and response to YM155 in clinical trials, and YM155 has been mostly abandoned for development despite favorable pharmacokinetic and toxicity profiles. Currently, alternative mechanisms are being explored for YM155 by a number of groups. In this study, ATC patient samples show overexpression of topoisomerase Top2α compared with benign thyroid samples and to differentiated thyroid cancers. ATC cell lines that overexpress Top2α are more sensitive to YM155. We created a YM155-resistant cell line, which shows decreased expression of Top2α and is resensitized with Top2α overexpression. Molecular modeling predicts binding for YM155 in the Top2α ATP-binding site and identifies key amino acids for YM155-Top2α interaction. A Top2α mutant abrogates the effect of YM155, confirming the contribution of Top2α to YM155 mechanism of action. Our results suggest a novel mechanism of action for YM155 and may represent a new therapeutic approach for the treatment of ATC.

The Continuum of Metastatic Prostate Cancer: Interpreting PSMA PET Findings in Recurrent Prostate Cancer.

Conventional imaging has been the standard imaging modality for assessing prostate cancer recurrence and is utilized to determine treatment response to therapy. Molecular imaging with PSMA PET-CT has proven to be more accurate, sensitive, and specific at identifying pelvic or distant metastatic disease, resulting in earlier diagnosis of advanced disease. Since advanced disease may not be seen on conventional imaging, due to its lower sensitivity, but can be identified by molecular imaging, this reveals that metastatic prostate cancer occurs on a continuum from negative PSMA PET-CT and negative conventional imaging to positive PSMA PET-CT and positive conventional imaging. Understanding this continuum, the accuracy of these modalities, and treatment related outcomes based on imaging, will allow the clinician to counsel patients on management. This review will highlight the differences in conventional and molecular imaging in prostate cancer and how PSMA PET-CT can be used for the management of prostate cancer patients in different clinical scenarios, while providing cautionary notes for overtreatment.

Patient-Derived Xenograft Engraftment and Breast Cancer Outcomes in a Prospective Neoadjuvant Study (BEAUTY).

PURPOSE: Patient-derived xenografts (PDX) are a research tool for studying cancer biology and drug response phenotypes. While engraftment rates are higher for tumors with more aggressive characteristics, it is uncertain whether engraftment is prognostic for cancer recurrence. PATIENTS AND METHODS: In a prospective study of patients with breast cancer treated with neoadjuvant chemotherapy (NAC) with taxane ± trastuzumab followed by anthracycline-based chemotherapy, we report the association between breast cancer events and PDX engraftment using tumors derived from treatment naïve (pre-NAC biopsies from 113 patients) and treatment resistant (post-NAC at surgery from 34 patients). Gray test was used to assess whether the cumulative incidence of a breast cancer event differs with respect to either pre-NAC PDX engraftment or post-NAC PDX engraftment. RESULTS: With a median follow-up of 5.7 years, the cumulative incidence of breast cancer relapse did not differ significantly according to pre-NAC PDX engraftment (5-year rate: 13.6% vs. 13.4%; P = 0.89). However, the incidence of a breast event was greater for patients with post-NAC PDX engraftment (5-year rate: 50.0% vs. 19.6%), but this did not achieve significance (P = 0.11). CONCLUSIONS: In treatment-naïve breast cancer receiving standard NAC, PDX engraftment was not prognostic for breast cancer recurrence. Further study is needed to establish whether PDX engraftment in the treatment-resistant setting is prognostic for cancer recurrence.

Ym155 Induces Oxidative Stress-Mediated DNA Damage and Cell Cycle Arrest, and Causes Programmed Cell Death in Anaplastic Thyroid Cancer Cells.

Anaplastic thyroid cancer (ATC) is one of the most lethal malignancies with a median survival time of about 4 months. Currently, there is no effective treatment, and the development of new therapies is an important and urgent issue for ATC patients. YM155 is a small molecule that was identified as the top candidate in a high-throughput screen of small molecule inhibitors performed against a panel of ATC cell lines by the National Cancer Institute. However, there were no follow-up studies investigating YM155 in ATC. Here, we determined the effects of YM155 on ATC and human primary benign thyroid cell (PBTC) survival with alamarBlue assay. Our data show that YM155 inhibited proliferation of ATC cell lines while sparing normal thyroid cells, suggesting a high therapeutic window. YM155-induced DNA damage was detected by measuring phosphorylation of γ-H2AX as a marker for DNA double-strand breaks. The formamidopyrimidine-DNA glycosylase (FPG)-modified alkaline comet assay in conjunction with reactive oxygen species (ROS) assay and glutathione (GSH)/glutathione (GSSG) assay suggests that YM155-mediated oxidative stress contributes to DNA damage. In addition, we provide evidence that YM155 causes cell cycle arrest in S phase and in the G2/M transition and causes apoptosis, as seen with flow cytometry. In this study, we show for the first time the multiple effects of YM155 in ATC cells, furthering a potential therapeutic approach for ATC.

Quantification and Optimization of Standard-of-Care Therapy to Delay the Emergence of Resistant Bone Metastatic Prostate Cancer.

BACKGROUND: Bone metastatic prostate cancer (BMPCa), despite the initial responsiveness to androgen deprivation therapy (ADT), inevitably becomes resistant. Recent clinical trials with upfront treatment of ADT combined with chemotherapy or novel hormonal therapies (NHTs) have extended overall patient survival. These results indicate that there is significant potential for the optimization of standard-of-care therapies to delay the emergence of progressive metastatic disease. METHODS: Here, we used data extracted from human bone metastatic biopsies pre- and post-abiraterone acetate/prednisone to generate a mathematical model of bone metastatic prostate cancer that can unravel the treatment impact on disease progression. Intra-tumor heterogeneity in regard to ADT and chemotherapy resistance was derived from biopsy data at a cellular level, permitting the model to track the dynamics of resistant phenotypes in response to treatment from biological first-principles without relying on data fitting. These cellular data were mathematically correlated with a clinical proxy for tumor burden, utilizing prostate-specific antigen (PSA) production as an example. RESULTS: Using this correlation, our model recapitulated the individual patient response to applied treatments in a separate and independent cohort of patients (n = 24), and was able to estimate the initial resistance to the ADT of each patient. Combined with an intervention-decision algorithm informed by patient-specific prediction of initial resistance, we propose to optimize the sequence of treatments for each patient with the goal of delaying the evolution of resistant disease and limit cancer cell growth, offering evidence for an improvement against retrospective data. CONCLUSIONS: Our results show how minimal but widely available patient information can be used to model and track the progression of BMPCa in real time, offering a clinically relevant insight into the patient-specific evolutionary dynamics of the disease and suggesting new therapeutic options for intervention. TRIAL REGISTRATION: NCT # 01953640. FUNDING: Funded by an NCI U01 (NCI) U01CA202958-01 and a Moffitt Team Science Award. CCL and DB were partly funded by an NCI PSON U01 (U01CA244101). AA was partly funded by a Department of Defense Prostate Cancer Research Program (W81XWH-15-1-0184) fellowship. LC was partly funded by a postdoctoral fellowship (PF-13-175-01-CSM) from the American Cancer Society.

Phase II trial of ribociclib and letrozole in patients with relapsed oestrogen receptor-positive ovarian or endometrial cancers.

OBJECTIVE: We describe a phase II clinical trial of the combination of ribociclib and letrozole for treatment of relapsed oestrogen receptor (ER)-positive ovarian cancer (OC) and endometrial cancer (EC). The primary endpoint was the proportion of patients alive, progression-free survival (PFS), and still on treatment at 12 weeks (PFS12), with 45% or greater considered positive. METHODS: Patients with measurable, relapsed ER-positive OC or EC (platinum-sensitive or resistant) were eligible and treated with 400 mg of oral ribociclib and 2.5 mg of oral letrozole daily. Patient-derived xenografts (PDXs) were created from imaging-guided tumour biopsies. RESULTS: Forty patients (20 OC and 20 EC) were enrolled. A PFS12 of 55% was observed in the EC cohort and 50% in the OC cohort. A PFS greater or equal to 24 weeks (PFS24) was seen in 20% (4/20) of the OC cohort and 35% (7/20) of the EC cohort. The greatest benefit was seen in low-grade serous OC (LGSOC) (3/3, 100% PFS24) and grades 1 and 2 EC (5/11, 45% PFS24). All three LGSOC patients obtained at least a partial response lasting for over 2 years, with two of the three patients still on treatment. PDX tumour engraftment was feasible in 45% of patients. Positive survival effects of the combination of ribociclib and letrozole were observed in two of three EC PDX models. CONCLUSION: Ribociclib and letrozole have promising clinical activity in relapsed ER-positive OC and EC, particularly in LGSOC and relapsed ER-positive grade 1 and 2 EC. Generation of PDX models is feasible with positive survival effects observed in EC models. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov registry (NCT02657928).

A Virtual Screening Platform Identifies Chloroethylagelastatin A as a Potential Ribosomal Inhibitor.

Chloroethylagelastatin A (CEAA) is an analogue of agelastatin A (AA), a natural alkaloid derived from a marine sponge. It is under development for therapeutic use against brain tumors as it has excellent central nervous system (CNS) penetration and pre-clinical therapeutic activity against brain tumors. Recently, AA was shown to inhibit protein synthesis by binding to the ribosomal A-site. In this study, we developed a novel virtual screening platform to perform a comprehensive screening of various AA analogues showing that AA analogues with proven therapeutic activity including CEAA have significant ribosomal binding capacity whereas therapeutically inactive analogues show poor ribosomal binding and revealing structural fingerprint features essential for drug-ribosome interactions. In particular, CEAA was found to have greater ribosomal binding capacity than AA. Biological tests showed that CEAA binds the ribosome and contributes to protein synthesis inhibition. Our findings suggest that CEAA may possess ribosomal inhibitor activity and that our virtual screening platform may be a useful tool in discovery and development of novel ribosomal inhibitors.

3D porous chitosan-chondroitin sulfate scaffolds promote epithelial to mesenchymal transition in prostate cancer cells.

Prostate cancer (PCa) is a common cancer in men that is curable prior to metastasis, when its prognosis worsens. Chondroitin sulfate (CS) is found in the extracellular matrix of normal prostate tissue and PCa, with greater content in metastatic PCa. Biomaterial scaffolds containing CS have yet to be evaluated for tumor microenvironment applications. Three-dimensional porous chitosan-CS (C-CS) scaffolds were developed and evaluated for PCa culture. Three C-CS scaffold compositions were prepared with 4 w/v% chitosan and 0.1, 0.5, and 1.0 w/v% CS and named 4-0.1, 4-0.5, and 4-1, respectively. The C-CS scaffolds had 90-95% porosity, average pore sizes between 143 and 166 µm, and no significant difference in scaffold stiffness. PC-3 and 22Rv1 PCa cells were cultured on the C-CS scaffolds to study the effect of CS on PCa growth and epithelial to mesenchymal transition (EMT). All C-CS scaffold compositions supported PCa growth and the 4-1 scaffolds had the greatest cell numbers for both PC-3 and 22Rv1. The C-CS scaffolds promoted upregulated EMT marker expression compared to 2D cultures with the greatest EMT marker expression in 4-1 scaffolds. Increasing CS concentration promoted upregulated vimentin expression in PC-3 cultures and N-cadherin and MMP-2 expression in 22Rv1 cultures. C-CS scaffolds promoted docetaxel drug resistance in PC-3 and 22Rv1 cultures and the 4-1 scaffold cultures had the greatest drug resistance. These results indicate that C-CS scaffolds are a promising in vitro platform for PCa.