Most patients with advanced triple-negative breast cancer (TNBC) develop drug resistance. MYC and MCL1 are frequently co-amplified in drug-resistant TNBC after neoadjuvant chemotherapy. Herein, we ...demonstrate that MYC and MCL1 cooperate in the maintenance of chemotherapy-resistant cancer stem cells (CSCs) in TNBC. MYC and MCL1 increased mitochondrial oxidative phosphorylation (mtOXPHOS) and the generation of reactive oxygen species (ROS), processes involved in maintenance of CSCs. A mutant of MCL1 that cannot localize in mitochondria reduced mtOXPHOS, ROS levels, and drug-resistant CSCs without affecting the anti-apoptotic function of MCL1. Increased levels of ROS, a by-product of activated mtOXPHOS, led to the accumulation of HIF-1α. Pharmacological inhibition of HIF-1α attenuated CSC enrichment and tumor initiation in vivo. These data suggest that (1) MYC and MCL1 confer resistance to chemotherapy by expanding CSCs via mtOXPHOS and (2) targeting mitochondrial respiration and HIF-1α may reverse chemotherapy resistance in TNBC.
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•MYC and MCL1 increase cancer stem cells in chemotherapy-resistant TNBC•MYC and MCL1 cooperatively promote mtOXPHOS, which in turn induces HIF-1α•MCL1 induces CSCs independent of its BH3-dependent, anti-apoptotic function•Inhibition of HIF1-α abolishes CSC enrichment in chemotherapy-resistant TNBC
MYC and MCL1 are co-amplified in drug-resistant breast cancer. Lee et al. reveal that MYC and MCL1 cooperate to maintain cancer stem cells (CSCs) resistant to chemotherapy by increasing mitochondrial OXPHOS, ROS production, and HIF-1α expression. Inhibition of HIF-1α blocks CSC expansion and restores chemotherapy sensitivity.
Distinct T cell infiltration patterns, i.e., immune infiltrated, excluded, and desert, result in different responses to cancer immunotherapies. However, the key determinants and biology underpinning ...these tumor immune phenotypes remain elusive. Here, we provide a high-resolution dissection of the entire tumor ecosystem through single-cell RNA-sequencing analysis of 15 ovarian tumors. Immune-desert tumors are characterized by unique tumor cell-intrinsic features, including metabolic pathways and low antigen presentation, and an enrichment of monocytes and immature macrophages. Immune-infiltrated and -excluded tumors differ markedly in their T cell composition and fibroblast subsets. Furthermore, our study reveals chemokine receptor-ligand interactions within and across compartments as potential mechanisms mediating immune cell infiltration, exemplified by the tumor cell-T cell cross talk via CXCL16-CXCR6 and stromal-immune cell cross talk via CXCL12/14-CXCR4. Our data highlight potential molecular mechanisms that shape the tumor immune phenotypes and may inform therapeutic strategies to improve clinical benefit from cancer immunotherapies.
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•OXPHOS and IFN gene sets are enriched in infiltrated and excluded tumor cells.•Pre-dysfunctional CD8+ GZMK T cells are enriched in excluded tumors.•FCN1 monocytes and immature MARCO macrophages are enriched in desert tumors.•CXCL16 is expressed primarily by infiltrated tumor cells and CXCR6 by T cells.
Hornburg et al. dissected the composition of the ovarian tumor microenvironment by scRNA-seq to define the underlying biology of the T cell infiltration pattern, namely the tumor immune phenotypes. The identified features, including the enrichment of immature myeloid cells in desert tumors, may help inform immunotherapeutic strategies in ovarian cancer.
"Triple negative" breast cancer (TNBC) is the most aggressive and least common clinical subtype of breast cancer. As its nomenclature implies, TNBC lacks specific biomarker expression marking ...response to an effective targeted therapy. The incidence of TNBC is higher in young minority women who suffer from high rates of early recurrence and death from their disease. Mounting preclinical evidence supports targeting the Ras/MAPK cell signaling pathway in the TNBC subtype, despite large genomic surveys such as The Cancer Genome Atlas demonstrating infrequent canonical mutations in this pathway. Due to the early spread of TNBC, targeted treatment in the neoadjuvant setting may offer the effective therapeutic punch needed to eliminate micro-metastatic disease and reduce mortality. Herein, we will review the evidence supporting clinical trials of targeted inhibitors of the Ras/MAPK pathway in TNBC, and discuss the obstacles and opportunities of this approach.
Inhibitors of the programmed cell death-1 (PD-1/PD-L1) signaling axis are approved to treat non-small cell lung cancer (NSCLC) patients, based on their significant overall survival (OS) benefit. ...Using transcriptomic analysis of 891 NSCLC tumors from patients treated with either the PD-L1 inhibitor atezolizumab or chemotherapy from two large randomized clinical trials, we find a significant B cell association with extended OS with PD-L1 blockade, independent of CD8+ T cell signals. We then derive gene signatures corresponding to the dominant B cell subsets present in NSCLC from single-cell RNA sequencing (RNA-seq) data. Importantly, we find increased plasma cell signatures to be predictive of OS in patients treated with atezolizumab, but not chemotherapy. B and plasma cells are also associated with the presence of tertiary lymphoid structures and organized lymphoid aggregates. Our results suggest an important contribution of B and plasma cells to the efficacy of PD-L1 blockade in NSCLC.
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•Three populations of intratumoral B and plasma cells identified by scRNA-seq in NSCLC•Plasma cells show the strongest predictive association with OS to PD-L1 blockade•Plasma cell benefits are independent of intratumoral CD8 T cells and PD-L1 expression•B and plasma cells are present in tertiary lymphoid structures in NSCLC tumors
Patil et al. utilize scRNA-seq of NSCLC tumors to identify three main populations of intratumoral B and plasma cells. Deconvolution of bulk RNA-seq of two large randomized NSCLC clinical trials demonstrates a strong association of increased intratumoral plasma cells with longer overall survival in patients treated with PD-L1 blockade, but not with chemotherapy.
Tumor-infiltrating lymphocytes (TIL) in the residual disease (RD) of triple-negative breast cancers (TNBC) after neoadjuvant chemotherapy (NAC) are associated with improved survival, but insight into ...tumor cell-autonomous molecular pathways affecting these features are lacking.
We analyzed TILs in the RD of clinically and molecularly characterized TNBCs after NAC and explored therapeutic strategies targeting combinations of MEK inhibitors with PD-1/PD-L1-targeted immunotherapy in mouse models of breast cancer.
Presence of TILs in the RD was significantly associated with improved prognosis. Genetic or transcriptomic alterations in Ras-MAPK signaling were significantly correlated with lower TILs. MEK inhibition upregulated cell surface MHC expression and PD-L1 in TNBC cells both in vivo and in vitro. Moreover, combined MEK and PD-L1/PD-1 inhibition enhanced antitumor immune responses in mouse models of breast cancer.
These data suggest the possibility that Ras-MAPK pathway activation promotes immune-evasion in TNBC, and support clinical trials combining MEK- and PD-L1-targeted therapies. Furthermore, Ras/MAPK activation and MHC expression may be predictive biomarkers of response to immune checkpoint inhibitors.
Triple-negative breast cancer (TNBC) is a heterogeneous subgroup of breast cancer that is associated with a poor prognosis. We evaluated the activity of CDK4/6 inhibitors across the TNBC subtypes and ...investigated mechanisms of sensitivity.
A panel of cell lines representative of TNBC was tested for
and
sensitivity to CDK4/6 inhibition. A fluorescent CDK2 activity reporter was used for single-cell analysis in conjunction with time-lapse imaging.
The luminal androgen receptor (LAR) subtype of TNBC was highly sensitive to CDK4/6 inhibition both
(
< 0.001 LAR vs. basal-like) and
in MDA-MB-453 LAR cell line xenografts. Single-cell analysis of CDK2 activity demonstrated differences in cell-cycle dynamics between LAR and basal-like cells. Palbociclib-sensitive LAR cells exit mitosis with low levels of CDK2 activity, into a quiescent state that requires CDK4/6 activity for cell-cycle reentry. Palbociclib-resistant basal-like cells exit mitosis directly into a proliferative state, with high levels of CDK2 activity, bypassing the restriction point and the requirement for CDK4/6 activity. High CDK2 activity after mitosis is driven by temporal deregulation of cyclin E1 expression. CDK4/6 inhibitors were synergistic with PI3 kinase inhibitors in
-mutant TNBC cell lines, extending CDK4/6 inhibitor sensitivity to additional TNBC subtypes.
Cell-cycle dynamics determine the response to CDK4/6 inhibition in TNBC. CDK4/6 inhibitors, alone and in combination, are a novel therapeutic strategy for specific subgroups of TNBC.
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Assessment of the immune response to tumors is growing in importance as the prognostic implications of this response are increasingly recognized, and as immunotherapies are evaluated and implemented ...in different tumor types. However, many different approaches can be used to assess and describe the immune response, which limits efforts at implementation as a routine clinical biomarker. In part 1 of this review, we have proposed a standardized methodology to assess tumor-infiltrating lymphocytes (TILs) in solid tumors, based on the International Immuno-Oncology Biomarkers Working Group guidelines for invasive breast carcinoma. In part 2 of this review, we discuss the available evidence for the prognostic and predictive value of TILs in common solid tumors, including carcinomas of the lung, gastrointestinal tract, genitourinary system, gynecologic system, and head and neck, as well as primary brain tumors, mesothelioma and melanoma. The particularities and different emphases in TIL assessment in different tumor types are discussed. The standardized methodology we propose can be adapted to different tumor types and may be used as a standard against which other approaches can be compared. Standardization of TIL assessment will help clinicians, researchers and pathologists to conclusively evaluate the utility of this simple biomarker in the current era of immunotherapy.
Estrogen receptor-positive (ER+) breast cancers frequently remain dependent on ER signaling even after acquiring resistance to endocrine agents, prompting the development of optimized ER antagonists. ...Fulvestrant is unique among approved ER therapeutics due to its capacity for full ER antagonism, thought to be achieved through ER degradation. The clinical potential of fulvestrant is limited by poor physicochemical features, spurring attempts to generate ER degraders with improved drug-like properties. We show that optimization of ER degradation does not guarantee full ER antagonism in breast cancer cells; ER “degraders” exhibit a spectrum of transcriptional activities and anti-proliferative potential. Mechanistically, we find that fulvestrant-like antagonists suppress ER transcriptional activity not by ER elimination, but by markedly slowing the intra-nuclear mobility of ER. Increased ER turnover occurs as a consequence of ER immobilization. These findings provide proof-of-concept that small molecule perturbation of transcription factor mobility may enable therapeutic targeting of this challenging target class.
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•Drug candidates optimized for ER degradation can weakly activate ER in cancer cells•“ER degraders” trigger interaction of ER with DNA at canonical binding sites•Impact on chromatin accessibility distinguishes ER antagonists from weak activators•Dramatic slowing of ER mobility drives ER antagonism, and precedes ER turnover
Ligands that limit estrogen receptor mobility exhibit superior anti-proliferative capacity compared to those aimed solely at promoting ER degradation, pointing to a distinct approach for developing treatments for ER+ breast cancer.
Assessment of tumor-infiltrating lymphocytes (TILs) in histopathologic specimens can provide important prognostic information in diverse solid tumor types, and may also be of value in predicting ...response to treatments. However, implementation as a routine clinical biomarker has not yet been achieved. As successful use of immune checkpoint inhibitors and other forms of immunotherapy become a clinical reality, the need for widely applicable, accessible, and reliable immunooncology biomarkers is clear. In part 1 of this review we briefly discuss the host immune response to tumors and different approaches to TIL assessment. We propose a standardized methodology to assess TILs in solid tumors on hematoxylin and eosin sections, in both primary and metastatic settings, based on the International Immuno-Oncology Biomarker Working Group guidelines for TIL assessment in invasive breast carcinoma. A review of the literature regarding the value of TIL assessment in different solid tumor types follows in part 2. The method we propose is reproducible, affordable, easily applied, and has demonstrated prognostic and predictive significance in invasive breast carcinoma. This standardized methodology may be used as a reference against which other methods are compared, and should be evaluated for clinical validity and utility. Standardization of TIL assessment will help to improve consistency and reproducibility in this field, enrich both the quality and quantity of comparable evidence, and help to thoroughly evaluate the utility of TILs assessment in this era of immunotherapy.
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