Ouathek Ouerfelli

Lineage plasticity is a cancer hallmark that drives disease progression and treatment resistance^1,2. Plasticity is often mediated by epigenetic mechanisms that may be reversible; however, there are few examples of such reversibility. In castration-resistant prostate cancer (CRPC), plasticity mediates resistance to androgen receptor (AR) inhibitors and progression from adenocarcinoma to aggressive subtypes, including neuroendocrine prostate cancer (CRPC-NE)^3,4,5. Here we show that plasticity-associated treatment resistance in CRPC can be reversed through the inhibition of NSD2, a histone methyltransferase⁶. NSD2 upregulation in CRPC-NE correlates with poor survival outcomes, and NSD2-mediated H3K36 dimethylation regulates enhancers of genes associated with neuroendocrine differentiation. In prostate tumour organoids established from genetically engineered mice⁷ that recapitulate the transdifferentiation to neuroendocrine states, and in human CRPC-NE organoids, CRISPR-mediated targeting of NSD2 reverts CRPC-NE to adenocarcinoma phenotypes. Moreover, a canonical AR program is upregulated and responses to the AR inhibitor enzalutamide are restored. Pharmacological inhibition of NSD2 with a first-in-class small molecule reverses plasticity and synergizes with enzalutamide to suppress growth and promote cell death in human patient-derived organoids of multiple CRPC subtypes in culture and in xenografts. Co-targeting of NSD2 and AR may represent a new therapeutic strategy for lethal forms of CRPC that are currently recalcitrant to treatment.

Most breast cancers depend on hormone-stimulated estrogen receptor alpha (ER) activity and are sensitive to ER inhibition. Resistance can arise from activating mutations in the gene encoding ER ( ESR1 ) or from reactivation of downstream targets. Newer ER antagonists occasionally show efficacy but are largely ineffective as single agents in the long term. Here, we show that ER translation is eIF4E/cap-independent yet sensitive to inhibitors of the translation initiation factor eIF4A. EIF4A inhibition reduces the expression of ER and cell cycle regulators such as cyclin D1. This leads to growth suppression in ligand-independent breast cancer models, including those driven by ER mutants and fusion proteins. Efficacy is enhanced by adding the ER degrader, fulvestrant. The combination further lowers ER expression and blocks tumor growth in vitro and in vivo. In an early clinical trial (NCT04092673), the eIF4A inhibitor zotatifin was combined with either fulvestrant or fulvestrant plus CDK4 inhibitor, abemaciclib, in patients with acquired resistance to these agents. Multiple clinical responses including a handful of durable regressions were observed, with little toxicity. Thus, eIF4A inhibition could be useful for treating ER+ breast cancer resistant to other modalities.

There is a compelling need to find drugs active against Mycobacterium tuberculosis ( Mtb ). 4′-Phosphopantetheinyl transferase (PptT) is an essential enzyme in Mtb that has attracted interest as a potential drug target. We optimized a PptT assay, used it to screen 422,740 compounds, and identified raltitrexed, an antineoplastic antimetabolite, as the most potent PptT inhibitor yet reported. While trying unsuccessfully to improve raltitrexed’s ability to kill Mtb and remove its ability to kill human cells, we learned three lessons that may help others developing antibiotics. First, binding of raltitrexed substantially changed the configuration of the PptT active site, complicating molecular modeling of analogs based on the unliganded crystal structure or the structure of cocrystals with inhibitors of another class. Second, minor changes in the raltitrexed molecule changed its target in Mtb from PptT to dihydrofolate reductase (DHFR). Third, the structure-activity relationship for over 800 raltitrexed analogs only became interpretable when we quantified and characterized the compounds’ intrabacterial accumulation and transformation.

We previously reported that activation of p53 by APR-246 reprograms tumor-associated macrophages to overcome immune checkpoint blockade resistance. Here, we demonstrate that APR-246 and its active moiety, methylene quinuclidinone (MQ) can enhance the immunogenicity of tumor cells directly. MQ treatment of murine B16F10 melanoma cells promoted activation of melanoma-specific CD8⁺T cells and increased the efficacy of a tumor cell vaccine using MQ-treated cells even when the B16F10 cells lacked p53. We then designed a novel combination of APR-246 with the TLR-4 agonist, monophosphoryl lipid A, and a CD40 agonist to further enhance these immunogenic effects and demonstrated a significant antitumor response. We propose that the immunogenic effect of MQ can be linked to its thiol-reactive alkylating ability as we observed similar immunogenic effects with the broad-spectrum cysteine-reactive compound, iodoacetamide. Our results thus indicate that combination of APR-246 with immunomodulatory agents may elicit effective antitumor immune response irrespective of the tumor’s p53 mutation status.

Colony-stimulating factor 1 (CSF1) is a primary regulator of the survival, proliferation, and differentiation of monocyte/macrophage that sustains the protumorigenic functions of tumor-associated macrophages (TAMs). Considering current advances in understanding the role of the inflammatory tumor microenvironment, targeting the components of the sarcoma microenvironment, such as TAMs, is a viable strategy. Here, we investigated the effect of PLX3397 (pexidartinib) as a potent inhibitor of the CSF1 receptor (CSF1R). PLX3397 was recently approved by the Food and Drug Administration (FDA) to treat tenosynovial giant cell tumor and reprogram TAMs whose infiltration correlates with unfavorable prognosis of sarcomas. First, we confirmed by cytokine arrays of tumor-conditioned media (TCM) that cytokines including CSF1 are secreted from LM8 osteosarcoma cells and NFSa fibrosarcoma cells. The TCM, like CSF1, stimulated ERK1/2 phosphorylation in bone marrow–derived macrophages (BMDMs), polarized BMDMs toward an M2 (TAM-like) phenotype, and strikingly promoted BMDM chemotaxis. In vitro administration of PLX3397 suppressed pERK1/2 stimulation by CSF1 or TCM, and reduced M2 polarization, survival, and chemotaxis in BMDMs. Systemic administration of PLX3397 to the osteosarcoma orthotopic xenograft model significantly suppressed the primary tumor growth and lung metastasis, and thus improved metastasis-free survival. PLX3397 treatment concurrently depleted TAMs and FOXP3+ regulatory T cells and, surprisingly, enhanced infiltration of CD8+ T cells into the microenvironments of both primary and metastatic osteosarcoma sites. Our preclinical results show that PLX3397 has strong macrophage- and T-cell–modulating effects that may translate into cancer immunotherapy for bone and soft-tissue sarcomas.

Colony-stimulating factor 1 (CSF1) is a primary regulator of the survival, proliferation, and differentiation of monocyte/macrophage that sustains the protumorigenic functions of tumor-associated macrophages (TAMs). Considering current advances in understanding the role of the inflammatory tumor microenvironment, targeting the components of the sarcoma microenvironment, such as TAMs, is a viable strategy. Here, we investigated the effect of PLX3397 (pexidartinib) as a potent inhibitor of the CSF1 receptor (CSF1R). PLX3397 was recently approved by the Food and Drug Administration (FDA) to treat tenosynovial giant cell tumor and reprogram TAMs whose infiltration correlates with unfavorable prognosis of sarcomas. First, we confirmed by cytokine arrays of tumor-conditioned media (TCM) that cytokines including CSF1 are secreted from LM8 osteosarcoma cells and NFSa fibrosarcoma cells. The TCM, like CSF1, stimulated ERK1/2 phosphorylation in bone marrow–derived macrophages (BMDMs), polarized BMDMs toward an M2 (TAM-like) phenotype, and strikingly promoted BMDM chemotaxis. In vitro administration of PLX3397 suppressed pERK1/2 stimulation by CSF1 or TCM, and reduced M2 polarization, survival, and chemotaxis in BMDMs. Systemic administration of PLX3397 to the osteosarcoma orthotopic xenograft model significantly suppressed the primary tumor growth and lung metastasis, and thus improved metastasis-free survival. PLX3397 treatment concurrently depleted TAMs and FOXP3+ regulatory T cells and, surprisingly, enhanced infiltration of CD8+ T cells into the microenvironments of both primary and metastatic osteosarcoma sites. Our preclinical results show that PLX3397 has strong macrophage- and T-cell–modulating effects that may translate into cancer immunotherapy for bone and soft-tissue sarcomas.

Supplementary data file shows supplementary methods and figures S1 to S7. Supplementary Figure S1 shows the establishment of the in vitro sarcoma TAM model. Supplementary Figure S2 shows the effect of anti-CSF-1 and anti-CSF-1R mAb and pazopanib on in vitro sarcoma TAMs. Supplementary Figure S3 show spontaneous lung metastasis in LM8 orthotopic osteosarcoma mouse model. Supplementary Figure S4 shows CSF-1R inhibition by PLX3397 blocks LM8-luc tumor growth and lung metastasis in orthotopic osteosarcoma mouse model. Supplementary Figure S5 shows toxicity assessment by body weight and blood chemistry per treatment group at the end of therapeutic experiments (day 22). Supplementary Figure S6 show histopathological examination of orthotopic osteosarcoma mouse models. Supplementary Figure S7 shows alteration of the TME composition in PLX3397-treated mice after CSF-1R inhibition

Supplementary Figure from Dual Fluorescence Isogenic Synthetic Lethal Kinase Screen and High-Content Secondary Screening for MUC16/CA125-Selective Agents

Supplementary data file shows supplementary methods and figures S1 to S7. Supplementary Figure S1 shows the establishment of the in vitro sarcoma TAM model. Supplementary Figure S2 shows the effect of anti-CSF-1 and anti-CSF-1R mAb and pazopanib on in vitro sarcoma TAMs. Supplementary Figure S3 show spontaneous lung metastasis in LM8 orthotopic osteosarcoma mouse model. Supplementary Figure S4 shows CSF-1R inhibition by PLX3397 blocks LM8-luc tumor growth and lung metastasis in orthotopic osteosarcoma mouse model. Supplementary Figure S5 shows toxicity assessment by body weight and blood chemistry per treatment group at the end of therapeutic experiments (day 22). Supplementary Figure S6 show histopathological examination of orthotopic osteosarcoma mouse models. Supplementary Figure S7 shows alteration of the TME composition in PLX3397-treated mice after CSF-1R inhibition