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Patients with EGFR- mutant non-small-cell lung cancer (NSCLC) have significantly benefited from the use of EGFR tyrosine kinase inhibitors (TKIs). However, long-term efficacy of these therapies is limited due to de novo resistance (~30%) as well as acquired resistance. Epithelial–mesenchymal transition transcription factors (EMT-TFs), have been identified as drivers of EMT-mediated resistance to EGFR TKIs, however, strategies to target EMT-TFs are lacking. As the third generation EGFR TKI, osimertinib, has now been adopted in the first-line setting, the frequency of T790M mutations will significantly decrease in the acquired resistance setting. Previously less common mechanisms of acquired resistance to first generation EGFR TKIs including EMT are now being observed at an increased frequency after osimertinib. Importantly, there are no other FDA approved targeted therapies after progression on osimertinib. Here, we investigated a novel strategy to overcome EGFR TKI resistance through targeting the EMT-TF, TWIST1, in EGFR- mutant NSCLC. We demonstrated that genetic silencing of TWIST1 or treatment with the TWIST1 inhibitor, harmine, resulted in growth inhibition and apoptosis in EGFR- mutant NSCLC. TWIST1 overexpression resulted in erlotinib and osimertinib resistance in EGFR -mutant NSCLC cells. Conversely, genetic and pharmacological inhibition of TWIST1 in EGFR TKI-resistant EGFR- mutant cells increased sensitivity to EGFR TKIs. TWIST1-mediated EGFR TKI resistance was due in part to TWIST1 suppression of transcription of the pro-apoptotic BH3-only gene, BCL2L11 (BIM), by directly binding to BCL2L11 intronic regions and promoter. As such, pan-BCL2 inhibitor treatment overcame TWIST1-mediated EGFR TKI resistance and were more effective in the setting of TWIST1 overexpression. Finally, in a mouse model of autochthonous EGFR -mutant lung cancer, Twist1 overexpression resulted in erlotinib resistance and suppression of erlotinib-induced apoptosis. These studies establish TWIST1 as a driver of resistance to EGFR TKIs and provide rationale for use of TWIST1 inhibitors or BCL2 inhibitors as means to overcome EMT-mediated resistance to EGFR TKIs.

How prostate cancer cells and their precursors mediate changes in the tumor microenvironment (TME) to drive prostate cancer progression is unclear, in part due to the inability to longitudinally study the disease evolution in human tissues. To overcome this limitation, we perform extensive single-cell RNA-sequencing (scRNA-seq) and molecular pathology of the comparative biology between human prostate cancer and key stages in the disease evolution of a genetically engineered mouse model (GEMM) of prostate cancer. Our studies of human tissues reveal that cancer cell-intrinsic activation of MYC signaling is a common denominator across the well-known molecular and pathological heterogeneity of human prostate cancer. Cell communication network and pathway analyses in GEMMs show that MYC oncogene-expressing neoplastic cells, directly and indirectly, reprogram the TME during carcinogenesis, leading to a convergence of cell state alterations in neighboring epithelial, immune, and fibroblast cell types that parallel key findings in human prostate cancer. Alterations in the tumour microenvironment (TME) can contribute to prostate cancer progression, but it is unclear how tumours mediate those changes. Here, analysis of human prostate cancer tissues and key stages of prostate cancer progression in a genetically engineered mouse model using single-cell RNA-sequencing reveals the central role of MYC signalling in reprogramming the TME.

The growing interest and clinical translation of alpha particle (α) therapies brings with it new challenges to assess target cell engagement and to monitor therapeutic effect. Noninvasive imaging has great potential to guide α-treatment and to harness the potential of these agents in the complex environment of disseminated disease. Poly(ADP) ribose polymerase 1 (PARP-1) is among the most abundantly expressed DNA repair enzymes with key roles in multiple repair pathways—such as those induced by irradiation. Here, we used a third-generation PARP1-specific radiotracer, [ 18 F]-PARPZ, to delineate castrate resistant prostate cancer xenografts. Following treatment with the clinically applied [ 225 Ac]-PSMA-617, positron emission tomography was performed and correlative autoradiography and histology acquired. [ 18 F]-PARPZ was able to distinguish treated from control (saline) xenografts by increased uptake. Kinetic analysis of tracer accumulation also suggests that the localization of the agent to sites of increased PARP-1 expression is a consequence of DNA damage response. Together, these data support expanded investigation of [ 18 F]-PARPZ to facilitate clinical translation in the ⍺-therapy space.

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children, with overall long-term survival rates of ∼65-70%. Thus, additional molecular insights and representative models are critical for identifying and evaluating new treatment modalities. Using MyoD-Cre-mediated introduction of mutant K-RasG12D and perturbations in p53, we developed a novel genetically engineered mouse model (GEMM) for RMS. The anatomic sites of primary RMS development recapitulated human disease, including tumors in the head, neck, extremities and abdomen. We confirmed RMS histology and diagnosis through Hematoxylin and Eosin staining, and positive immunohistochemical staining for desmin, myogenin, and phosphotungstic acid–Hematoxylin. Cell lines from GEMM tumors were established with the ability to engraft in immunocompetent mice with comparable histological and staining features as the primary tumors. Tail vein injection of cell lines had high metastatic potential to the lungs. Transcriptomic analyses of p53R172H/K-RasG12D GEMM-derived tumors showed evidence of high molecular homology with human RMS. Finally, pre-clinical use of these murine RMS lines showed similar therapeutic responsiveness to chemotherapy and targeted therapies as human RMS cell lines.

BackgroundProstate cancer remains the second leading cause of cancer related death in men. Immune check point blocking antibodies have revolutionized treatment of multiple solid tumors, but results in prostate cancer remain marginal. Previous reports have suggested that local therapies, in particular cryoablation might increase tumor immunogenicity. In this work, we examine potential synergism between tumor cryoabalation and check point blocking antibodies.MethodsFVB/NJ mice were injected subcutaneously into each flank with either 1 × 106 or 0.2 × 106 isogenic hormone sensitive Myc-Cap cells to establish synchronous grafts. Mice were treated with four intraperitoneal injections of anti-PD-1 (10 mg/kg), anti-CTLA-4 (1 mg/kg), or isotype control antibody with or without adjuvant cryoablation of the larger tumor graft and with or without neo-adjuvant androgen deprivation with degarelix (ADT). Mouse survival and growth rates of tumor grafts were measured. The immune dependency of observed oncological effects was evaluated by T cell depletion experiments.ResultsTreatment with anti-CTLA-4 antibody and cryoablation delayed the growth of the distant tumor by 14.8 days (p = 0.0006) and decreased the mortality rate by factor of 4 (p = 0.0003) when compared to cryoablation alone. This synergy was found to be dependent on CD3+ and CD8+ cells. Combining PD-1 blockade with cryoablation did not show a benefit over use of either treatment alone. Addition of ADT to anti-PD1 therapy and cryoablation doubled the time to accelerated growth in the untreated tumors (p = 0.0021) and extended survival when compared to cryoablation combined with ADT in 25% of the mice. Effects of combining anti-PD1 with ADT and cryoablation on mouse survival were obviated by T cell depletion.ConclusionTrimodal therapy consisting of androgen deprivation, cryoablation and PD-1 blockade, as well as the combination of cryoablation and low dose anti-CTLA-4 blockade showed that local therapies with cryoablation could be considered to augment the effects of checkpoint blockade in prostate cancer.

The microenvironment of prostate cancer often includes abundant tumor-associated macrophages (TAMs), with their acquisition of an M2 phenotype correlating with local aggressiveness and metastasis. Tumor-derived M-CSF contributes to TAM M2 polarization, and M-CSF receptor inhibition slows prostate cancer growth in model systems. As additional cytokines can direct TAM M2 polarization, targeting downstream transcription factors could avoid resistance. Klf4 and C/EBPβ each contribute to monocyte development, and reduced expression of macrophage Klf4 or C/EBPβ favors their adoption of a pro-inflammatory M1 state. We find that a Hi-Myc C57BL/6 prostate cancer line grows more slowly in syngeneic Klf4(f/f);Lys-Cre compared with Klf4(f/f) mice when inoculated subcutaneously, but grows equally rapidly in C/EBPβ(f/f);Lys-Cre and C/EBPβ(f/f) hosts. In the absence of myeloid Klf4, TAMs have reduced expression of surface mannose receptor and Fizz1 mRNA, both M2 markers. Global gene expression analysis further revealed activation of pro-inflammatory, pro-atherosclerotic pathways. Analysis of tumor-infiltrating lymphocytes (TILs) demonstrated markedly increased activated CD8 T cell numbers, and CD8 T cell depletion obviated the inhibitory effect of myeloid Klf4 deletion on prostate cancer growth. These findings suggest that reducing expression or activity of the Klf4 transcription factor in tumor myeloid cells may contribute to prostate cancer therapy.

A defining hallmark of primary and metastatic cancers is the migration and invasion of malignant cells. These invasive properties involve altered dynamics of the cytoskeleton and one of its major structural components β-actin. Here we identify AIM1 (absent in melanoma 1) as an actin-binding protein that suppresses pro-invasive properties in benign prostate epithelium. Depletion of AIM1 in prostate epithelial cells increases cytoskeletal remodeling, intracellular traction forces, cell migration and invasion, and anchorage-independent growth. In addition, decreased AIM1 expression results in increased metastatic dissemination in vivo. AIM1 strongly associates with the actin cytoskeleton in prostate epithelial cells in normal tissues, but not in prostate cancers. In addition to a mislocalization of AIM1 from the actin cytoskeleton in invasive cancers, advanced prostate cancers often harbor AIM1 deletion and reduced expression. These findings implicate AIM1 as a key suppressor of invasive phenotypes that becomes dysregulated in primary and metastatic prostate cancer. Invasion of malignant cells involves changes in cytoskeleton dynamics. Here the authors identify absent in melanoma 1 as an actin binding protein and show that it regulates cytoskeletal remodeling and cell migration in prostate epithelial cells, acting as a metastatic suppressor in cancer cells.

Prostate cancer is the second leading cause of cancer death among United States men. However, disease aggressiveness is varied, with low-grade disease often being indolent and high-grade cancer accounting for the greatest density of deaths. Outcomes are also disparate among men with high-grade prostate cancer, with upwards of 65% having disease recurrence even after primary treatment. Identification of men at risk for recurrence and elucidation of the molecular processes that drive their disease is paramount, as these men are the most likely to benefit from multimodal therapy. We previously showed that androgen-induced expression profiles in prostate development are reactivated in aggressive prostate cancers. Herein, we report the down-regulation of one such gene, Sparcl1, a secreted protein, acidic and rich in cysteine (SPARC) family matricellular protein, during invasive phases of prostate development and regeneration. We further demonstrate a parallel process in prostate cancer, with decreased expression of SPARCL1 in high-grade/metastatic prostate cancer. Mechanistically, we demonstrate that SPARCL1 loss increases the migratory and invasive properties of prostate cancer cells through Ras homolog gene family, member C (RHOC), a known mediator of metastatic progression. By using models incorporating clinicopathologic parameters to predict prostate cancer recurrence after treatment, we show that SPARCL1 loss is a significant, independent prognostic marker of disease progression. Thus, SPARCL1 is a potent regulator of cell migration/invasion and its loss is independently associated with prostate cancer recurrence.

Mutant KRAS drives glycolytic flux in lung cancer, potentially impacting aberrant protein glycosylation. Recent evidence suggests aberrant KRAS drives flux of glucose into the hexosamine biosynthetic pathway (HBP). HBP is required for various glycosylation processes, such as protein N- or O-glycosylation and glycolipid synthesis. However, its function during tumorigenesis is poorly understood. One contributor and proposed target of KRAS-driven cancers is a developmentally conserved epithelial plasticity program called epithelial-mesenchymal transition (EMT). Here we showed in novel autochthonous mouse models that EMT accelerated KrasG12D lung tumorigenesis by upregulating expression of key enzymes of the HBP pathway. We demonstrated that HBP was required for suppressing KrasG12D-induced senescence, and targeting HBP significantly delayed KrasG12D lung tumorigenesis. To explore the mechanism, we investigated protein glycosylation downstream of HBP and found elevated levels of O-linked β-N-acetylglucosamine (O-GlcNAcylation) posttranslational modification on intracellular proteins. O-GlcNAcylation suppressed KrasG12D oncogene-induced senescence (OIS) and accelerated lung tumorigenesis. Conversely, loss of O-GlcNAcylation delayed lung tumorigenesis. O-GlcNAcylation of proteins SNAI1 and c-MYC correlated with the EMT-HBP axis and accelerated lung tumorigenesis. Our results demonstrated that O-GlcNAcylation was sufficient and required to accelerate KrasG12D lung tumorigenesis in vivo, which was reinforced by epithelial plasticity programs.

ELL-associated factor 2 (EAF2) is an androgen-responsive tumor suppressor frequently deleted in advanced prostate cancer that functions as a transcription elongation factor of RNA Pol II through interaction with the ELL family proteins. EAF2 knockout mice on a 129P2/OLA-C57BL/6J background developed late-onset lung adenocarcinoma, hepatocellular carcinoma, B-cell lymphoma and high-grade prostatic intraepithelial neoplasia. In order to further characterize the role of EAF2 in the development of prostatic defects, the effects of EAF2 loss were compared in different murine strains. In the current study, aged EAF2(-/-) mice on both the C57BL/6J and FVB/NJ backgrounds exhibited mPIN lesions as previously reported on a 129P2/OLA-C57BL/6J background. In contrast to the 129P2/OLA-C57BL/6J mixed genetic background, the mPIN lesions in C57BL/6J and FVB/NJ EAF2(-/-) mice were associated with stromal defects characteristic of a reactive stroma and a statistically significant increase in prostate microvessel density. Stromal inflammation and increased microvessel density was evident in EAF2-deficient mice on a pure C57BL/6J background at an early age and preceded the development of the histologic epithelial hyperplasia and neoplasia found in the prostates of older EAF2(-/-) animals. Mice deficient in EAF2 had an increased recovery rate and a decreased overall response to the effects of androgen deprivation. EAF2 expression in human cancer was significantly down-regulated and microvessel density was significantly increased compared to matched normal prostate tissue; furthermore EAF2 expression was negatively correlated with microvessel density. These results suggest that the EAF2 knockout mouse on the C57BL/6J and FVB/NJ genetic backgrounds provides a model of PIN lesions associated with an altered prostate microvasculature and reactive stromal compartment corresponding to that reported in human prostate tumors.