Cellular and molecular mechanisms of plasticity in cancer

CRACD loss induces neuroendocrine cell plasticity of lung adenocarcinoma

Tumor cell plasticity contributes to intratumoral heterogeneity and therapy resistance. Through cell plasticity, some lung adenocarcinoma (LUAD) cells transform into neuroendocrine (NE) tumor cells. However, the mechanisms of NE cell plasticity remain unclear. CRACD (capping protein inhibiting regulator of actin dynamics), a capping protein inhibitor, is frequently inactivated in cancers. CRACD knockout (KO) is sufficient to de-repress NE-related gene expression in the pulmonary epithelium and LUAD cells. In LUAD mouse models, Cracd KO increases intratumoral heterogeneity with NE gene expression. Single-cell transcriptomic analysis showed that Cracd KO-induced NE cell plasticity is associated with cell de-differentiation and stemness-related pathway activation. The single-cell transcriptomic analysis of LUAD patient tumors recapitulates that the distinct LUAD NE cell cluster expressing NE genes is co-enriched with impaired actin remodeling. This study reveals the crucial role of CRACD in restricting NE cell plasticity that induces cell de-differentiation of LUAD.

The roles of PD-L1 in the various stages of tumor metastasis

The interaction between tumor programmed death ligand 1 (PD-L1) and T-cell programmed cell death 1 (PD-1) has long been acknowledged as a mechanism for evading immune surveillance. Recent studies, however, have unveiled a more nuanced role of tumor-intrinsic PD-L1 in reprograming tumoral phenotypes. Preclinical models emphasize the synchronized effects of both intracellular and extracellular PD-L1 in promoting metastasis, with intricate interactions with the immune system. This review aims to summarize recent findings to elucidate the spatiotemporal heterogeneity of PD-L1 expression and the pro-metastatic roles of PD-L1 in the entire process of tumor metastasis. For example, PD-L1 regulates the epithelial-to-mesenchymal transition (EMT) process, facilitates the survival of circulating tumor cells, and induces the formation of immunosuppressive environments at pre-metastatic niches and metastatic sites. And the complexed and dynamic regulation process of PD-L1 for tumor metastasis is related to the spatiotemporal heterogeneity of PD-L1 expression and functions from tumor primary sites to various metastatic sites. This review extends the current understandings for the roles of PD-L1 in mediating tumor metastasis and provides new insights into therapeutic decisions in clinical practice.

Decoding the principle of cell-fate determination for its reverse control

Understanding and manipulating cell fate determination is pivotal in biology. Cell fate is determined by intricate and nonlinear interactions among molecules, making mathematical model-based quantitative analysis indispensable for its elucidation. Nevertheless, obtaining the essential dynamic experimental data for model development has been a significant obstacle. However, recent advancements in large-scale omics data technology are providing the necessary foundation for developing such models. Based on accumulated experimental evidence, we can postulate that cell fate is governed by a limited number of core regulatory circuits. Following this concept, we present a conceptual control framework that leverages single-cell RNA-seq data for dynamic molecular regulatory network modeling, aiming to identify and manipulate core regulatory circuits and their master regulators to drive desired cellular state transitions. We illustrate the proposed framework by applying it to the reversion of lung cancer cell states, although it is more broadly applicable to understanding and controlling a wide range of cell-fate determination processes.

B7-H3 at the crossroads between tumor plasticity and colorectal cancer progression: a potential target for therapeutic intervention

B7-H3 (B7 homology 3 protein) is an important transmembrane immunoregulatory protein expressed in immune cells, antigen-presenting cells, and tumor cells. Studies reveal a multifaceted role of B7-H3 in tumor progression by modulating various cancer hallmarks involving angiogenesis, immune evasion, and tumor microenvironment, and it is also a promising candidate for cancer immunotherapy. In colorectal cancer (CRC), B7-H3 has been associated with various aspects of disease progression, such as evasion of tumor immune surveillance, tumor-node metastasis, and poor prognosis. Strategies to block or interfere with B7-H3 in its immunological and non-immunological functions are under investigation. In this study, we explore the role of B7-H3 in tumor plasticity, emphasizing tumor glucose metabolism, angiogenesis, epithelial-mesenchymal transition, cancer stem cells, apoptosis, and changing immune signatures in the tumor immune landscape. We discuss how B7-H3-induced tumor plasticity contributes to immune evasion, metastasis, and therapy resistance. Furthermore, we delve into the most recent advancements in targeting B7-H3-based tumor immunotherapy as a potential approach to CRC treatment.

Targeting vimentin: a multifaceted approach to combatting cancer metastasis and drug resistance

This comprehensive review explores vimentin as a pivotal therapeutic target in cancer treatment, with a primary focus on mitigating metastasis and overcoming drug resistance. Vimentin, a key player in cancer progression, is intricately involved in processes such as epithelial-to-mesenchymal transition (EMT) and resistance mechanisms to standard cancer therapies. The review delves into diverse vimentin inhibition strategies. Precision tools, including antibodies and nanobodies, selectively neutralize vimentin's pro-tumorigenic effects. DNA and RNA aptamers disrupt vimentin-associated signaling pathways through their adaptable binding properties. Innovative approaches, such as vimentin-targeted vaccines and microRNAs (miRNAs), harness the immune system and post-transcriptional regulation to combat vimentin-expressing cancer cells. By dissecting vimentin inhibition strategies across these categories, this review provides a comprehensive overview of anti-vimentin therapeutics in cancer treatment. It underscores the growing recognition of vimentin as a pivotal therapeutic target in cancer and presents a diverse array of inhibitors, including antibodies, nanobodies, DNA and RNA aptamers, vaccines, and miRNAs. These multifaceted approaches hold substantial promise for tackling metastasis and overcoming drug resistance, collectively presenting new avenues for enhanced cancer therapy.

Bivalent chromatin: a developmental balancing act tipped in cancer

Bivalent chromatin is defined by the co-occurrence of otherwise opposing H3K4me3 and H3K27me3 modifications and is typically located at unmethylated promoters of lowly transcribed genes. In embryonic stem cells, bivalent chromatin has been proposed to poise developmental genes for future activation, silencing or stable repression upon lineage commitment. Normally, bivalent chromatin is kept in tight balance in cells, in part through the activity of the MLL/COMPASS-like and Polycomb repressive complexes that deposit the H3K4me3 and H3K27me3 modifications, respectively, but also emerging novel regulators including DPPA2/4, QSER1, BEND3, TET1 and METTL14. In cancers, both the deregulation of existing domains and the creation of de novo bivalent states is associated with either the activation or silencing of transcriptional programmes. This may facilitate diverse aspects of cancer pathology including epithelial-to-mesenchymal plasticity, chemoresistance and immune evasion. Here, we review current methods for detecting bivalent chromatin and discuss the factors involved in the formation and fine-tuning of bivalent domains. Finally, we examine how the deregulation of chromatin bivalency in the context of cancer could facilitate and/or reflect cancer cell adaptation. We propose a model in which bivalent chromatin represents a dynamic balance between otherwise opposing states, where the underlying DNA sequence is primed for the future activation or repression. Shifting this balance in any direction disrupts the tight equilibrium and tips cells into an altered epigenetic and phenotypic space, facilitating both developmental and cancer processes.

Tumor-educated Gr1+CD11b+ cells drive breast cancer metastasis via OSM/IL-6/JAK-induced cancer cell plasticity

Cancer cell plasticity contributes to therapy resistance and metastasis, which represent the main causes of cancer-related death, including in breast cancer. The tumor microenvironment drives cancer cell plasticity and metastasis, and unraveling the underlying cues may provide novel strategies for managing metastatic disease. Using breast cancer experimental models and transcriptomic analyses, we show that stem cell antigen-1 positive (SCA1+) murine breast cancer cells enriched during tumor progression and metastasis had higher in vitro cancer stem cell-like properties, enhanced in vivo metastatic ability, and generated tumors rich in Gr1hiLy6G+CD11b+ cells. In turn, tumor-educated Gr1+CD11b+ (Tu-Gr1+CD11b+) cells rapidly and transiently converted low metastatic SCA1- cells into highly metastatic SCA1+ cells via secreted oncostatin M (OSM) and IL-6. JAK inhibition prevented OSM/IL-6-induced SCA1+ population enrichment, while OSM/IL-6 depletion suppressed Tu-Gr1+CD11b+-induced SCA1+ population enrichment in vitro and metastasis in vivo. Moreover, chemotherapy-selected highly metastatic 4T1 cells maintained high SCA1+ positivity through autocrine IL-6 production, and in vitro JAK inhibition blunted SCA1 positivity and metastatic capacity. Importantly, Tu-Gr1+CD11b+ cells invoked a gene signature in tumor cells predicting shorter overall survival (OS), relapse-free survival (RFS), and lung metastasis in breast cancer patients. Collectively, our data identified OSM/IL-6/JAK as a clinically relevant paracrine/autocrine axis instigating breast cancer cell plasticity and triggering metastasis.

A Multiplexed Approach to Assess Small Cell Lung Cancer Subtype Heterogeneity in Primary and Patient-Derived Tumor Samples

Unlocking the heterogeneity of cancers is crucial for developing therapeutic approaches that effectively eradicate disease. As our understanding of markers specific to cancer subclones or subtypes expands, there is a growing demand for advanced technologies that enable the simultaneous investigation of multiple targets within an individual tumor sample. Indeed, multiplex approaches offer distinct benefits, particularly when tumor specimens are small and scarce. Here we describe the utility of two fluorescence-based multiplex approaches; fluorescent Western blots, and multiplex immunohistochemistry (Opal™) staining to interrogate heterogeneity, using small cell lung cancer as an example. Critically, the coupling of Opal™ staining with advanced image quantitation, permits the dissection of cancer cell phenotypes at a single cell level. These approaches can be applied to patient biopsies and/or patient-derived xenograft (PDX) models and serve as powerful methodologies for assessing tumor cell heterogeneity in response to therapy or between metastatic lesions across diverse tissue sites.

Quenching thirst with poison? Paradoxical effect of anticancer drugs

Anticancer drugs have been developed with expectations to provide long-term or at least short-term survival benefits for patients with cancer. Unfortunately, drug therapy tends to provoke malignant biological and clinical behaviours of cancer cells relating not only to the evolution of resistance to specific drugs but also to the enhancement of their proliferation and metastasis abilities. Thus, drug therapy is suspected to impair long-term survival in treated patients under certain circumstances. The paradoxical therapeutic effects could be described as 'quenching thirst with poison', where temporary relief is sought regardless of the consequences. Understanding the underlying mechanisms by which tumours react on drug-induced stress to maintain viability is crucial to develop rational targeting approaches which may optimize survival in patients with cancer. In this review, we describe the paradoxical adverse effects of anticancer drugs, in particular how cancer cells complete resistance evolution, enhance proliferation, escape from immune surveillance and metastasize efficiently when encountered with drug therapy. We also describe an integrative therapeutic framework that may diminish such paradoxical effects, consisting of four main strategies: (1) targeting endogenous stress response pathways, (2) targeting new identities of cancer cells, (3) adaptive therapy- exploiting subclonal competition of cancer cells, and (4) targeting tumour microenvironment.

Ruthenium-Catalyzed Chemo-Selective Carbene Insertion into C-H Bond of Styrene over Cyclopropanation: C-C Bond Formation

The C-C bond formation reactions are important in organic synthesis. Heck reaction is known to arylate the terminal carbon of olefins; however, direct alkylation of the terminal carbon of olefin is limited. Herein, we report a novel ruthenium-catalyzed selective cross-coupling reaction of styrene and α-diazoesters to form a new C-C bond over cyclopropanation via the C-H insertion process for the first time. Using this novel methodology, a wide variety of substrates have been utilized and a variety of α-vinylated benzylic esters and densely functionalized olefins have been synthesized with good stereoselectivity under mild reaction conditions. The overall reaction process proceeds through the carbene insertion into styrene to form the desired products in good to excellent yields with proper stereoselectivity. The selective C-H inserted product, wide substrate scope, and excellent functional group tolerance are the best features of this work.

β-catenin/CBP activation of mTORC1 signaling promotes partial epithelial-mesenchymal states in head and neck cancer

Head and neck cancers, which include oral squamous cell carcinoma (OSCC) as a major subsite, exhibit cellular plasticity that includes features of an epithelial-mesenchymal transition (EMT), referred to as partial-EMT (p-EMT). To identify molecular mechanisms contributing to OSCC plasticity, we performed a multiphase analysis of single cell RNA sequencing (scRNAseq) data from human OSCC. This included a multiresolution characterization of cancer cell subgroups to identify pathways and cell states that are heterogeneously represented, followed by casual inference analysis to elucidate activating and inhibitory relationships between these pathways and cell states. This approach revealed signaling networks associated with hierarchical cell state transitions, which notably included an association between β-catenin-driven CREB-binding protein (CBP) activity and mTORC1 signaling. This network was associated with subpopulations of cancer cells that were enriched for markers of the p-EMT state and poor patient survival. Functional analyses revealed that β-catenin/CBP induced mTORC1 activity in part through the transcriptional regulation of a raptor-interacting protein, chaperonin containing TCP1 subunit 5 (CCT5). Inhibition of β-catenin-CBP activity through the use of the orally active small molecule, E7386, reduced the expression of CCT5 and mTORC1 activity in vitro, and inhibited p-EMT-associated markers and tumor development in a murine model of OSCC. Our study highlights the use of multiresolution network analyses of scRNAseq data to identify targetable signals for therapeutic benefit, thus defining an underappreciated association between β-catenin/CBP and mTORC1 signaling in head and neck cancer plasticity.

The integrated stress response in cancer progression: a force for plasticity and resistance

During their quest for growth, adaptation, and survival, cancer cells create a favorable environment through the manipulation of normal cellular mechanisms. They increase anabolic processes, including protein synthesis, to facilitate uncontrolled proliferation and deplete the tumor microenvironment of resources. As a dynamic adaptation to the self-imposed oncogenic stress, cancer cells promptly hijack translational control to alter gene expression. Rewiring the cellular proteome shifts the phenotypic balance between growth and adaptation to promote therapeutic resistance and cancer cell survival. The integrated stress response (ISR) is a key translational program activated by oncogenic stress that is utilized to fine-tune protein synthesis and adjust to environmental barriers. Here, we focus on the role of ISR signaling for driving cancer progression. We highlight mechanisms of regulation for distinct mRNA translation downstream of the ISR, expand on oncogenic signaling utilizing the ISR in response to environmental stresses, and pinpoint the impact this has for cancer cell plasticity during resistance to therapy. There is an ongoing need for innovative drug targets in cancer treatment, and modulating ISR activity may provide a unique avenue for clinical benefit.

High CD142 Level Marks Tumor-Promoting Fibroblasts with Targeting Potential in Colorectal Cancer

Colorectal cancer (CRC) has a high incidence and is one of the leading causes of cancer-related death. The accumulation of cancer-associated fibroblasts (CAF) induces an aggressive, stem-like phenotype in tumor cells, and it indicates a poor prognosis. However, cellular heterogeneity among CAFs and the targeting of both stromal and CRC cells are not yet well resolved. Here, we identified CD142high fibroblasts with a higher stimulating effect on CRC cell proliferation via secreting more hepatocyte growth factor (HGF) compared to CD142low CAFs. We also found that combinations of inhibitors that had either a promising effect in other cancer types or are more active in CRC compared to normal colonic epithelium acted synergistically in CRC cells. Importantly, heat shock protein 90 (HSP90) inhibitor selected against CD142high fibroblasts, and both CRC cells and CAFs were sensitive to a BCL-xL inhibitor. However, targeting mitogen-activated protein kinase kinase (MEK) was ineffective in fibroblasts, and an epigenetic inhibitor selected for a tumor cell population with markers of aggressive behavior. Thus, we suggest BCL-xL and HSP90 inhibitors to eliminate cancer cells and decrease the tumor-promoting CD142high CAF population. This may be the basis of a strategy to target both CRC cells and stromal fibroblasts, resulting in the inhibition of tumor relapse.

Epigenetic plasticity cooperates with cell-cell interactions to direct pancreatic tumorigenesis

The response to tumor-initiating inflammatory and genetic insults can vary among morphologically indistinguishable cells, suggesting as yet uncharacterized roles for epigenetic plasticity during early neoplasia. To investigate the origins and impact of such plasticity, we performed single-cell analyses on normal, inflamed, premalignant, and malignant tissues in autochthonous models of pancreatic cancer. We reproducibly identified heterogeneous cell states that are primed for diverse, late-emerging neoplastic fates and linked these to chromatin remodeling at cell-cell communication loci. Using an inference approach, we revealed signaling gene modules and tissue-level cross-talk, including a neoplasia-driving feedback loop between discrete epithelial and immune cell populations that was functionally validated in mice. Our results uncover a neoplasia-specific tissue-remodeling program that may be exploited for pancreatic cancer interception.

CRACD suppresses neuroendocrinal plasticity of lung adenocarcinoma

Tumor cell plasticity contributes to intratumoral heterogeneity and therapy resistance. Through cell plasticity, lung adenocarcinoma (LUAD) cells transform into neuroendocrinal (NE) tumor cells. However, the mechanisms of NE cell plasticity remain unclear. CRACD, a capping protein inhibitor, is frequently inactivated in cancers. CRACD knock-out (KO) de-represses NE-related gene expression in the pulmonary epithelium and LUAD cells. In LUAD mouse models, Cracd KO increases intratumoral heterogeneity with NE gene expression. Single-cell transcriptomic analysis showed that Cracd KO-induced NE plasticity is associated with cell de-differentiation and activated stemness-related pathways. The single-cell transcriptomes of LUAD patient tumors recapitulate that the distinct LUAD NE cell cluster expressing NE genes is co-enriched with SOX2, OCT4, and NANOG pathway activation, and impaired actin remodeling. This study reveals an unexpected role of CRACD in restricting NE cell plasticity that induces cell de-differentiation, providing new insights into cell plasticity of LUAD.

Metastasis

Most cancer-associated deaths occur due to metastasis, yet our understanding of metastasis as an evolving, heterogeneous, systemic disease and of how to effectively treat it is still emerging. Metastasis requires the acquisition of a succession of traits to disseminate, variably enter and exit dormancy, and colonize distant organs. The success of these events is driven by clonal selection, the potential of metastatic cells to dynamically transition into distinct states, and their ability to co-opt the immune environment. Here, we review the main principles of metastasis and highlight emerging opportunities to develop more effective therapies for metastatic cancer.

Organoid modeling reveals the tumorigenic potential of the alveolar progenitor cell state

Alveolar type 2 (AT2) cells, the epithelial progenitor cells of the distal lung, are known to be the prominent cell of origin for lung adenocarcinoma. The regulatory programs that control chromatin and gene expression in AT2 cells during the early stages of tumor initiation are not well understood. Here, we dissected the response of AT2 cells to Kras activation and p53 loss (KP) using combined single cell RNA and ATAC sequencing in an established tumor organoid system. Multi-omic analysis showed that KP tumor organoid cells exhibit two major cellular states: one more closely resembling AT2 cells (SPC-high) and another with loss of AT2 identity (hereafter, Hmga2-high). These cell states are characterized by unique transcription factor (TF) networks, with SPC-high states associated with TFs known to regulate AT2 cell fate during development and homeostasis, and distinct TFs associated with the Hmga2-high state. CD44 was identified as a marker of the Hmga2-high state, and was used to separate organoid cultures for functional comparison of these two cell states. Organoid assays and orthotopic transplantation studies indicated that SPC-high cells have higher tumorigenic capacity in the lung microenvironment compared to Hmga2-high cells. These findings highlight the utility of understanding chromatin regulation in the early oncogenic versions of epithelial cells, which may reveal more effective means to intervene the progression of Kras-driven lung cancer.

Relationship between Tumor Infiltrating Immune Cells and Tumor Metastasis and Its Prognostic Value in Cancer

Tumor metastasis is an important reason for the difficulty of tumor treatment. Besides the tumor cells themselves, the tumor microenvironment plays an important role in the process of tumor metastasis. Tumor infiltrating immune cells (TIICs) are one of the main components of TME and plays an important role in every link of tumor metastasis. This article mainly reviews the role of tumor-infiltrating immune cells in epithelial mesenchymal transformation, extracellular matrix remodeling, tumor angiogenesis and formation of pre-metastatic niche. The value of TIICs in the prognosis of cervical cancer, lung cancer and breast cancer was also discussed. We believe that accurate prognosis of cancer treatment outcomes is conducive to further improving treatment regimens, determining personalized treatment strategies, and ultimately achieving successful cancer treatment. This paper elucidates the relationship between tumor and TIICs in order to explore the function of immune cells in different diseases and provide new ideas for the treatment of cancer.

Ten Years of CRISPRing Cancers In Vitro

Cell lines have always constituted a good investigation tool for cancer research, allowing scientists to understand the basic mechanisms underlying the complex network of phenomena peculiar to the transforming path from a healthy to cancerous cell. The introduction of CRISPR in everyday laboratory activity and its relative affordability greatly expanded the bench lab weaponry in the daily attempt to better understand tumor biology with the final aim to mitigate cancer's impact in our lives. In this review, we aim to report how this genome editing technique affected in the in vitro modeling of different aspects of tumor biology, its several declinations, and analyze the advantages and drawbacks of each of them.

Systematic Comparison of Pancreatic Ductal Adenocarcinoma Models Identifies a Conserved Highly Plastic Basal Cell State

Intratumoral heterogeneity and cellular plasticity have emerged as hallmarks of cancer, including pancreatic ductal adenocarcinoma (PDAC). As PDAC portends a dire prognosis, a better understanding of the mechanisms underpinning cellular diversity in PDAC is crucial. Here, we investigated the cellular heterogeneity of PDAC cancer cells across a range of in vitro and in vivo growth conditions using single-cell genomics. Heterogeneity contracted significantly in two-dimensional and three-dimensional cell culture models but was restored upon orthotopic transplantation. Orthotopic transplants reproducibly acquired cell states identified in autochthonous PDAC tumors, including a basal state exhibiting coexpression and coaccessibility of epithelial and mesenchymal genes. Lineage tracing combined with single-cell transcriptomics revealed that basal cells display high plasticity in situ. This work defines the impact of cellular growth conditions on phenotypic diversity and uncovers a highly plastic cell state with the capacity to facilitate state transitions and promote intratumoral heterogeneity in PDAC.

SIGNIFICANCE

This work provides important insights into how different model systems of pancreatic ductal adenocarcinoma mold the phenotypic space of cancer cells, highlighting the power of in vivo models.