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Current therapy for glioblastoma multiforme (GBM), the highest grade malignant brain tumor, is mostly ineffective, and better preclinical model systems are needed to increase the successful translation of drug discovery efforts to the clinic. Previous work described a genetically engineered mouse (GEM) model which contains perturbations in the most frequently aberrant networks in GBM (driven by RB, KRAS/PI3K signaling and PTEN), that induce development of Grade IV astrocytoma with human disease properties. Here, we developed and characterized an orthotopic mouse model derived from the GEM that retains the features of the GEM model in an immunocompetent background, but is tractable and efficient for preclinical evaluation of candidate therapeutic regimens. Orthotopic brain tumors are highly proliferative, invasive, vascular, and express histologic markers characteristic of human GBM. Primary tumor cells were examined for sensitivity to chemotherapeutics and targeted drugs. PI3K and MAPK pathway inhibitors used as single agents inhibited cell proliferation but did not result in significant apoptosis. However, in combination, these inhibitors resulted in a substantial increase in cell death. Moreover, these findings translated to the in vivo orthotopic model: PI3K or MAPK inhibitor treatment regimens resulted in incomplete pathway suppression and feedback loops, whereas dual treatment delayed tumor growth through increased apoptosis and decreased tumor cell proliferation. Analysis of downstream pathway components revealed a cooperative effect on target downregulation. These concordant results, together with the morphologic similarities to human GBM disease characteristics of the model, validate it as a new platform for the evaluation of GBM treatment.

Despite epidermal growth factor receptor (EGFR) is a pivotal oncogene for several cancers, including lung adenocarcinoma (LUAD), how it senses extracellular matrix (ECM) rigidity remain elusive in the context of the increasing role of tissue rigidity on various hallmarks of cancer development. Here it is shown that EGFR dictates tumorigenic agrin expression in lung cancer cell lines, genetically engineered EGFR‐driven mouse models, and human specimens. Agrin expression confers substrate stiffness‐dependent oncogenic attributes to EGFR‐reliant cancer cells. Mechanistically, agrin mechanoactivates EGFR through epidermal growth factor (EGF)‐dependent and independent modes, thereby sensitizing its activity toward localized cancer cell‐ECM adherence and bulk rigidity by fostering interactions with integrin β1. Notably, a feed‐forward loop linking agrin–EGFR rigidity response to YAP–TEAD mechanosensing is essential for tumorigenesis. Together, the combined inhibition of EGFR–YAP/TEAD may offer a strategy to reduce lung tumorigenesis by disrupting agrin‐EGFR mechanotransduction, uncovering a therapeutic vulnerability for EGFR‐addicted lung cancers. The study identifies agrin‐EGFR mechanotransduction as a critical driver of lung adenocarcinoma which enhances EGFR signaling through an integrin‐FAK‐actomyosin dependent positive feedback on YAP/TAZ ‐TEAD in response to matrix stiffness. Targeting this oncogenic loop through combinatorial treatments inhibits lung cancer due to agrin impairment. Thus, agrin may serve as a biomarker for predicting response to these therapies.

Molecular subtypes of small cell lung cancer (SCLC) defined by the expression of key transcription regulators have recently been proposed in cell lines and limited number of primary tumors. The clinical and biological implications of neuroendocrine (NE) subtypes in metastatic SCLC, and the extent to which they vary within and between patient tumors and in patient-derived models is not known. We integrate histology, transcriptome, exome, and treatment outcomes of SCLC from a range of metastatic sites, revealing complex intra- and intertumoral heterogeneity of NE differentiation. Transcriptomic analysis confirms previously described subtypes based on ASCL1 , NEUROD1 , POU2F3 , YAP1 , and ATOH1 expression, and reveal a clinical subtype with hybrid NE and non-NE phenotypes, marked by chemotherapy-resistance and exceedingly poor outcomes. NE tumors are more likely to have RB1 , NOTCH , and chromatin modifier gene mutations, upregulation of DNA damage response genes, and are more likely to respond to replication stress targeted therapies. In contrast, patients preferentially benefited from immunotherapy if their tumors were non-NE. Transcriptional phenotypes strongly skew towards the NE state in patient-derived model systems, an observation that was confirmed in paired patient-matched tumors and xenografts. We provide a framework that unifies transcriptomic and genomic dimensions of metastatic SCLC. The marked differences in transcriptional diversity between patient tumors and model systems are likely to have implications in development of novel therapeutic agents. Molecular subtypes of small cell lung cancer characterized by neuroendocrine differentiation have been described in cell lines and primary tumors. The clinical implications of neuroendocrine subtypes in metastatic and relapsed tumors, and the extent to which the subtype distribution is recapitulated in patient-derived models remains unclear. Here, the authors integrated genomics and transcriptomics on 100 small cell cancers from a range of metastatic sites finding complex intra- and intertumoral heterogeneity, notably not recapitulated in patient-derived model systems, and distinct therapeutic vulnerabilities associated with neuroendocrine subtypes.

Although immunotherapy has revolutionized cancer treatment, only a subset of patients demonstrate durable clinical benefit. Definitive predictive biomarkers and targets to overcome resistance remain unidentified, underscoring the urgency to develop reliable immunocompetent models for mechanistic assessment. Here we characterize a panel of syngeneic mouse models, representing a variety of molecular and phenotypic subtypes of human melanomas and exhibiting their diverse range of responses to immune checkpoint blockade (ICB). Comparative analysis of genomic, transcriptomic and tumor-infiltrating immune cell profiles demonstrated alignment with clinical observations and validated the correlation of T cell dysfunction and exclusion programs with resistance. Notably, genome-wide expression analysis uncovered a melanocytic plasticity signature predictive of patient outcome in response to ICB, suggesting that the multipotency and differentiation status of melanoma can determine ICB benefit. Our comparative preclinical platform recapitulates melanoma clinical behavior and can be employed to identify mechanisms and treatment strategies to improve patient care. Genetically engineered mouse models representing the spectrum of human cutaneous melanoma provide a platform for studying clinical responses to immunotherapy.

Preclinical therapeutic assessment currently relies on the growth response of established human cell lines xenografted into immunocompromised mice, a strategy that is generally not predictive of clinical outcomes. Immunocompetent genetically engineered mouse (GEM)-derived tumor allograft models offer highly tractable preclinical alternatives and facilitate analysis of clinically promising immunomodulatory agents. Imageable reporters are essential for accurately tracking tumor growth and response, particularly for metastases. Unfortunately, reporters such as luciferase and GFP are foreign antigens in immunocompetent mice, potentially hindering tumor growth and confounding therapeutic responses. Here we assessed the value of reporter-tolerized GEMs as allograft recipients by targeting minimal expression of a luciferase-GFP fusion reporter to the anterior pituitary gland (dubbed the \"Glowing Head\" or GH mouse). The luciferase-GFP reporter expressed in tumor cells induced adverse immune responses in wildtype mouse, but not in GH mouse, as transplantation hosts. The antigenicity of optical reporters resulted in a decrease in both the growth and metastatic potential of the labeled tumor in wildtype mice as compared to the GH mice. Moreover, reporter expression can also alter the tumor response to chemotherapy or targeted therapy in a context-dependent manner. Thus the GH mice and experimental approaches vetted herein provide concept validation and a strategy for effective, reproducible preclinical evaluation of growth and response kinetics for traceable tumors.

The high mortality rate from ovarian cancers can be attributed to late-stage diagnosis and lack of effective treatment. Despite enormous effort to develop better targeted therapies, platinum-based chemotherapy still remains the standard of care for ovarian cancer patients, and resistance occurs at a high rate. One of the rate limiting factors for translation of new drug discoveries into clinical treatments has been the lack of suitable preclinical cancer models with high predictive value. We previously generated genetically engineered mouse (GEM) models based on perturbation of Tp53 and Rb with or without Brca1 or Brca2 that develop serous epithelial ovarian cancer (SEOC) closely resembling the human disease on histologic and molecular levels. Here, we describe an adaptation of these GEM models to orthotopic allografts that uniformly develop tumors with short latency and are ideally suited for routine preclinical studies. Ovarian tumors deficient in Brca1 respond to treatment with cisplatin and olaparib, a PARP inhibitor, whereas Brca1-wild type tumors are non-responsive to treatment, recapitulating the relative sensitivities observed in patients. These mouse models provide the opportunity for evaluation of effective therapeutics, including prediction of differential responses in Brca1-wild type and Brca1-deficient tumors and development of relevant biomarkers.

Small‐cell lung cancer (SCLC) is the most lethal type of lung cancer. Specifically, MYC‐driven non‐neuroendocrine SCLC is particularly resistant to standard therapies. Lurbinectedin was recently approved for the treatment of relapsed SCLC, but combinatorial approaches are needed to increase the depth and duration of responses to lurbinectedin. Using high‐throughput screens, we found inhibitors of ataxia telangiectasia mutated and rad3 related (ATR) as the most effective agents for augmenting lurbinectedin efficacy. First‐in‐class ATR inhibitor berzosertib synergized with lurbinectedin in multiple SCLC cell lines, organoid, and in vivo models. Mechanistically, ATR inhibition abrogated S‐phase arrest induced by lurbinectedin and forced cell cycle progression causing mitotic catastrophe and cell death. High CDKN1A /p21 expression was associated with decreased synergy due to G1 arrest, while increased levels of ERCC5 /XPG were predictive of increased combination efficacy. Importantly, MYC‐driven non‐neuroendocrine tumors which are resistant to first‐line therapies show reduced CDKN1A /p21 expression and increased ERCC5 /XPG indicating they are primed for response to lurbinectedin–berzosertib combination. The combination is being assessed in a clinical trial NCT04802174. Synopsis We found that the DNA damaging RNA Pol‐II inhibitor lurbinectedin strongly synergizes with the ATR inhibitor berzosertib in SCLC. This synergy is dependent on berzosertib allowing for continued cell cycle progression in the presence of lurbinectedin induced DNA damage. An unbiased screen revealed maximal synergy between lurbinectedin and the ATR inhibitor berzosertib in SCLC cells. Berzosertib augments lurbinectedin‐induced DNA damage while inhibiting cell cycle checkpoints leading to mitotic catastrophe. Synergy is reduced with high p21 expression as p21 causes G1 arrest. Synergy is increased with high XPG expression as lurbinectedin induced DNA damage is XPG dependent. The recalcitrant non‐neuroendocrine SCLC subtype has high XPG expression and low p21 expression leading to a unique vulnerability to the lurbinectedin‐berzosertib combination, we are currently exploring this combination in the clinic. Graphical Abstract We found that the DNA damaging RNA Pol‐II inhibitor lurbinectedin strongly synergizes with the ATR inhibitor berzosertib in small cell lung cancer. This synergy is dependent on berzosertib allowing for continued cell cycle progression in the presence of lurbinectedin induced DNA damage.

Background Kaposi sarcoma (KS) is a multicentric tumor caused by Kaposi sarcoma herpesvirus (KSHV) that leads to morbidity and mortality among people with HIV worldwide. KS commonly involves the skin but can occur in the gastrointestinal tract (GI) in severe cases. Methods RNA sequencing was used to compare the cellular and KSHV gene expression signatures of skin and GI KS lesions in 44 paired samples from 19 participants with KS alone or with concurrent KSHV-associated diseases. Analyses of KSHV expression from KS lesions identified transcriptionally active areas of the viral genome. Results The transcript of an essential viral lytic gene, ORF75, was detected in 91% of KS lesions. Analyses of host genes identified 370 differentially expressed genes (DEGs) unique to skin KS and 58 DEGs unique to GI KS lesions as compared to normal tissue. Interleukin (IL)-6 and IL-10 gene expression were higher in skin lesions as compared to normal skin but not in GI KS lesions. Twenty-six cellular genes were differentially expressed in both skin and GI KS tissues: these included Fms-related tyrosine kinase 4 ( FLT4) , encoding an angiogenic receptor, and Stanniocalcin 1 ( STC1) , a secreted glycoprotein . FLT4 and STC1 were further investigated in functional studies using primary lymphatic endothelial cells (LECs). In these models, KSHV infection of LECs led to increased tubule formation that was impaired upon knock-down of STC1 or FLT4 . Conclusions This study of transcriptional profiling of KS tissue provides novel insights into the characteristics and pathogenesis of this unique virus-driven neoplasm.

Background Breast cancer is a heterogenous disease with several histological and molecular subtypes. Models that represent these subtypes are essential for translational research aimed at improving clinical strategy for targeted therapeutics. Methods Different combinations of genetic aberrations ( Brca1 and Trp53 loss, and inhibition of proteins of the Rb family) were induced in the mammary gland by injection of adenovirus expressing Cre recombinase into the mammary ducts of adult genetically engineered mice. Mammary tumors with different genetic aberrations were classified into molecular subtypes based on expression of molecular markers and RNAseq analysis. In vitro potency assays and Western blots were used to examine their drug sensitivities. Results Induction of Brca1 and Trp53 loss in mammary ductal epithelium resulted in development of basal-like hormone receptor (HR)-negative mammary tumors. Inhibition of Rb and Trp53 loss or the combination of Rb , Trp53 and Brca1 aberrations resulted in development of luminal ductal carcinoma positive for ER, PR, and Her2 expression. HR positivity in tumors with Rb , Trp53 and Brca1 aberrations indicated that functionality of the Rb pathway rather than Brca1 status affected HR status in these models. Mammary tumor gene expression profiles recapitulated human basal-like or luminal B breast cancer signatures, but HR-positive luminal cancer models were endocrine resistant and exhibited upregulation of PI3K signaling and sensitivity to this pathway inhibition. Furthermore, both tumor subtypes were resistant to CDK4/6 inhibition. Conclusions Examination of molecular expression profiles and drug sensitivities of tumors indicate that these breast cancer models can be utilized as a translational platform for evaluation of targeted combinations to improve chemotherapeutic response in patients that no longer respond to hormone therapy or that are resistant to CDK4/6 inhibition.

A Correction to this paper has been published: https://doi.org/10.1038/s41591-021-01252-6.