Molecular Cancer Research最新文献

TIPE is a protein highly expressed in various cancers that promotes ferroptosis in colorectal cancer cells. Ferroptosis is a nonapoptotic cell death caused by lipid peroxidation, and microsomal glutathione transferase 1 (MGST1) is a critical enzyme that resists lipid peroxidation. This study explored how TIPE regulates MGST1 expression to inhibit ferroptosis and promote colorectal cancer proliferation. TIPE was highly expressed in colorectal cancer tissues and positively correlated with the proliferation of human colorectal cancer cells. We measured levels of reactive oxygen species and lipid reactive oxygen species in colorectal cancer cells with differential expression of TIPE and detected ferroptosis using transmission electron microscopy. Bioinformatics analysis revealed a positive correlation of expression patterns between TIPE and MGST1 in colorectal cancer. TIPE regulated the expression of MGST1 by activating the phosphorylation of ERK1/2. Coimmunoprecipitation revealed binding between MGST1 and ALOX5. This binding inhibited the phosphorylation of ALOX5, inhibiting ferroptosis and promoting the proliferation of colorectal cancer cells. A tumor formation experiment in nude mice supported our findings that TIPE regulates the proliferation of colorectal cancer by regulating ferroptosis. Implications: TIPE inhibits colorectal cancer ferroptosis via an MGST1-ALOX5 interaction to promote colorectal cancer proliferation. These findings suggest future colorectal cancer treatment strategies.

Colorectal cancer tumors start as polyps on the inner lining of the colorectum, in which they are exposed to the mechanics of peristalsis. Our previous work leveraged a custom-built peristalsis bioreactor to demonstrate that colonic peristalsis led to cancer stem cell enrichment in colorectal cancer cells. However, this malignant mechanotransductive response was confined to select colorectal cancer lines that harbored an oncogenic mutation in the Kirsten rat sarcoma virus (KRAS) gene. In this study, we explored the involvement of activating KRAS mutations on peristalsis-associated mechanotransduction in colorectal cancer. Peristalsis enriched cancer stem cell marker Leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) in KRAS mutant lines in a Wnt ligand-independent manner. Conversely, LGR5 enrichment in wild-type KRAS lines exposed to peristalsis were minimal. LGR5 enrichment downstream of peristalsis translated to increased tumorigenicity in vivo. Differences in mechanotransduction were apparent via unbiased gene set enrichment analysis, in which many unique pathways were enriched in wild-type versus mutant lines. Peristalsis also triggered β-catenin nuclear localization independent of Wnt ligands, particularly in KRAS mutant lines. The involvement of KRAS was validated via gain and loss of function strategies. Peristalsis-induced β-catenin activation and LGR5 enrichment depended on the activation of the MEK/ERK cascade. Taken together, our results demonstrated that oncogenic KRAS mutations conferred a unique peristalsis-associated mechanotransduction response to colorectal cancer cells, resulting in cancer stem cell enrichment and increased tumorigenicity. These mechanosensory connections can be leveraged in improving the sensitivity of emerging therapies that target oncogenic KRAS. Implications: Oncogenic KRAS empowers colorectal cancer cells to harness the mechanics of colonic peristalsis for malignant gain independent of other cooperating signals.

Approximately 70% of oropharyngeal squamous carcinomas (OPSCC) are associated with human papillomavirus (HPV). Although patients with HPV-positive (HPV+) tumors generally have better outcomes than those with HPV-negative tumors, a subset of HPV+ positive patients do have poor outcomes. Our previous work suggested that tumors with integrated virus exhibit significantly greater genome-wide genomic instability than those with only episomal viral genomes, and patients with HPV+ OPSCC with episomal viral genomes had better outcomes. To explore the causal relation between viral integration and genomic instability, we have examined the time course of viral integration and genetic instability in tonsillar keratinocytes transformed with HPV16. HPV-infected human tonsil keratinocyte cell lines were continuously passaged, and every fifth passage, some cells were retained for genomic analysis. Whole-genome sequencing and optical genomic mapping confirmed that virus integrated in five of six cell lines while remaining episomal in the sixth. In all lines, genome instability occurred during early passages but essentially ceased following viral integration; however, it continued to occur in later passages in the episomal line. To test tumorigenicity of the cell lines, cells were injected subcutaneously into the flanks of nude mice. A cell line with the integrated virus induced tumors following injection in the nude mouse whereas that with the episomal virus did not. Implications: Genomic instability in HPV OPSCC tumors is not the result of viral integration but likely promotes integration. Moreover, transformants with episomal virus seem to be less tumorigenic than those with integrated virus.

Cholangiocarcinoma (CCA) is a rare cancer that arises from the bile duct and is broadly classified by the location of the tumor as either intrahepatic cholangiocarcinoma (iCCA) or extrahepatic cholangiocarcinoma (eCCA). Immunotherapy has revolutionized cancer treatment, yet its utility in CCA has been limited as the tumor microenvironment (TME) in CCA is poorly understood compared with other common cancers. Utilizing previously published transcriptome data, our reanalysis has revealed that CCA has one of the highest relative levels of NK cells, a potent cytotoxic immune cell, compared with other cancers. However, despite iCCA and eCCA having comparable relative levels of NK infiltration, NK cell infiltration only correlated with survival in patients with eCCA. Our subsequent investigation revealed that although iCCA and eCCA profoundly altered NK activity, eCCA had a significantly reduced impact on NK functionality. Whereas iCCA was resistant to long-term NK coculture, eCCA was markedly more sensitive. Moreover, although both iCCA and eCCA dysregulated key NK-activating receptors, eCCA coculture did not impact NKp30 nor NKp44 expression. Furthermore, tumor transcriptome analysis of NKHigh CCA samples revealed a modulation of multiple immune and nonimmune cell types within the TME. Implications: These studies are the first to investigate how iCCA and eCCA impact NK cell functionality through shared and distinct mechanisms and how elevated NK cell infiltration could shape the CCA TME in a subtype-dependent manner.

Despite aggressive, multimodal therapies, the prognosis of patients with refractory or recurrent rhabdomyosarcoma (RMS) has not improved in four decades. Because RMS resembles skeletal muscle precursor cells, differentiation-inducing therapy has been proposed for patients with advanced disease. In RAS-mutant PAX fusion-negative RMS (FN-RMS) preclinical models, MEK1/2 inhibition (MEKi) induces differentiation, slows tumor growth, and extends survival. However, the response is short-lived. A better understanding of the molecular mechanisms regulating FN-RMS differentiation could improve differentiation therapy. In this study, we identified a role in FN-RMS differentiation for ASAP1, an ADP ribosylation factor (ARF) GTPase-activating protein (GAP) with both proinvasive and tumor-suppressor functions. We found that ASAP1 knockdown inhibited differentiation in FN-RMS cells. Interestingly, knockdown of the GTPases ARF1 or ARF5, targets of ASAP1 GAP activity, also blocked differentiation of FN-RMS. We discovered that loss of ARF pathway components blocked myogenic transcription factor expression. Therefore, we examined the effects on transcriptional regulators. MEKi led to the phosphorylation and inactivation of WW domain-containing transcriptional regulator 1 (WWTR1; TAZ), a homolog of the pro-proliferative transcriptional co-activator YAP1, regulated by the Hippo pathway. However, loss of ASAP1 or ARF1 blocked this inactivation, which inhibits MEKi-induced differentiation. Finally, MEKi-induced differentiation was rescued by dual knockdown of ASAP1 and WWTR1. This study shows that ASAP1 and ARF1 are necessary for myogenic differentiation, providing a deeper understanding of differentiation in FN-RMS and illuminating an opportunity to advance differentiation therapy. Implications: ASAP1 and ARF1 regulate MEKi-induced differentiation of FN-RMS cells by modulating WWTR1 (TAZ) activity, supporting YAP1/TAZ inhibition as a FN-RMS differentiation therapy strategy.

Pediatric high-grade gliomas (PHGG) are aggressive, undifferentiated central nervous system tumors with poor outcomes, for which no standard-of-care drug therapy currently exists. Through a knockdown (KD) screen for epigenetic regulators, we identified PRMT5 as essential for PHGG cell growth. We hypothesized that, similar to its effect in normal cells, PRMT5 promotes self-renewal of stem-like PHGG tumor-initiating cells essential for tumor growth. We conducted in vitro analyses, including limiting dilution studies of self-renewal, to determine the phenotypic effects of PRMT5 KD. We performed chromatin immunoprecipitation sequencing (ChIP-Seq) to identify PRMT5-mediated epigenetic changes and performed gene set enrichment analysis to identify pathways that PRMT5 regulates. Using an orthotopic xenograft model of PHGG, we tracked survival and histologic characteristics resulting from PRMT5 KD or administration of a PRMT5 inhibitor ± radiation therapy. In vitro, PRMT5 KD slowed cell-cycle progression, tumor growth and self-renewal, and altered chromatin occupancy at genes associated with differentiation, tumor formation, and growth. In vivo, PRMT5 KD increased survival and reduced tumor aggressiveness; however, pharmacologic inhibition of PRMT5 with or without radiation therapy did not improve survival. PRMT5 KD epigenetically reduced tumor-initiating cells' self-renewal, leading to increased survival in preclinical models. Pharmacologic inhibition of PRMT5 enzymatic activity may have failed in vivo due to insufficient reduction of PRMT5 activity by chemical inhibition, or this failure may suggest that nonenzymatic activities of PRMT5 are more relevant. Implications: PRMT5 maintains and promotes the growth of stem-like cells that initiate and drive tumorigenesis in PHGG.

Metastasis accounts for the overwhelming majority of cancer deaths. In prostate cancer and many other solid tumors, progression to metastasis is associated with drastically reduced survival outcomes, yet the mechanisms behind this progression remain largely unknown. ATAD2 (ATPase family AAA domain containing 2) is an epigenetic reader of acetylated histones that is overexpressed in multiple cancer types and usually associated with poor patient outcomes. However, the functional role of ATAD2 in cancer progression and metastasis has been relatively understudied. Here we employ genetically engineered mouse models of prostate cancer bone metastasis, as well as multiple independent human cohorts, to show that ATAD2 is highly enriched in bone metastasis compared to primary tumors and significantly associated with the development of metastasis. We show that ATAD2 expression is associated with MYC pathway activation in patient datasets and that, at least in a subset of tumors, MYC and ATAD2 can regulate each other's expression. Using functional studies on mouse bone metastatic cell lines and innovative organ-on-a-chip bone invasion assays, we establish a functional role for ATAD2 inhibition in diminishing prostate cancer metastasis and growth in bone. Implications: Our study highlights ATAD2 as a driver of prostate cancer progression and metastasis and suggests it may constitute a promising novel therapeutic target.

The complex composition and dynamic change of the tumor microenvironment (TME), mainly consisting of tumor cells, immune cells, stromal cells and extracellular components, significantly impedes the effector function of cytotoxic T cells (CTLs) and thus represents a major obstacle for tumor immunotherapies. In this review, we summarize and discuss the impacts and underlying mechanisms of major elements in the TME (different cell types, extracellular matrix, nutrients and metabolites, etc.) on the infiltration, survival and effector functions of T cells, mainly CD8+ CTLs. Moreover, we also highlight recent advances that may potentiate endogenous anti-tumor immunity and improve the efficacy of T-cell based immunotherapies in cancer patients by manipulating components inside/outside of the TME. A deeper understanding of the effects and action mechanisms of TME components on the tumor-eradicating ability of CTLs may pave the way for discovering new targets to augment endogenous anti-tumor immunity and for designing combinational therapeutic regimens to enhance the efficacy of tumor immunotherapies in clinic.

Kaposi Sarcoma (KS) is a frequently aggressive malignancy caused by Kaposi sarcoma herpesvirus (KSHV/HHV-8). People with immunodeficiencies, including HIV, are at increased risk for developing KS, but our understanding of the contributions of the cellular genome to KS pathogenesis remains limited. To determine if there are cellular genetic alterations in KS that might provide biological or therapeutic insights, we performed whole exome sequencing on 78 KS tumors and matched normal control skin from 59 adults with KS (46 with HIV-associated KS and 13 with HIV-negative KS) receiving treatment at the Uganda Cancer Institute in Kampala, Uganda. We found a very low mutational burden in all but one specimen (median=11 mutations), which is the lowest number of mutations among all 33 tumor types in The Cancer Genome Atlas (TCGA). No recurrent mutations were seen and the most commonly affected oncogenic pathway was RTK/RAS. Mutational signatures included defective DNA mismatch repair and smoking. There was no evidence suggesting that multiple tumors from the same patient originated from the same original clone. The number of genome copy alterations per genome were higher in tumors from those without HIV infection and in tumors from participants with advanced stage disease, suggesting that lesions that take longer to develop may accumulate more alterations, although the number of alterations remain low compared to other cancers. Implications: Our findings indicate that the pathogenesis of KS differs from other malignancies, and that the primary driver of carcinogenesis is KSHV viral infection and expression of viral oncogenes, rather than clonal oncogenic transformation.

Malignant neoplasms arise within a region of chronic inflammation caused by tissue injuries. Inflammation is a key factor involved in all aspects of tumorigenesis including initiation, proliferation, invasion, angiogenesis, and metastasis. Interleukin-1 (IL-1) plays critical functions in tumor development with influencing the tumor microenvironment and promoting cancer progression. However, the mechanism of continuous activation of IL-1-mediated inflammatory pathway in tumor has not been fully elucidated. This study provides a novel mechanism of the autocrine activation of IL-1 signaling in squamous cell carcinoma (SCC) through a novel oncoprotein, TSC-22 homologous gene-1 (THG-1, also known as TSD22D4). The RNA sequencing analysis revealed that THG-1 overexpression enhances the transcription of NF-κB targets including IL1A, IL1B, TNFA, and IL8. Furthermore, THG-1 knockdown reduced the responsiveness to IL-1 through suppression of NF-κB nuclear translocation. To elucidate the mechanism, we focused on a THG-1 interacting protein, NRBP1. We found that NRBP1 facilitates the degradation of TRAF6 through its E3 ubiquitin ligase activity. THG-1 bound to NRBP1 and suppressed the degradation of TRAF6. Furthermore, THG-1 knockdown reduced TRAF6 abundance and NF-κB activity in SCC cells. Public database analyses of head and neck SCC revealed that high expression of THG-1 is associated with activation of the IL-1 and TNF pathways, which share TRAF6 in the signal transductions. Finally, THG-1 abundance in laryngeal SCC specimens is elevated in patients with recurrence. These results indicated that THG-1 drives the self-sufficiency of IL-1-mediated inflammatory pathway, which could contribute to the future diagnosis and immune therapy of SCCs. Implications: An oncoprotein THG-1/TSD22D4 activates the IL-1-mediated inflammatory pathway through suppression of TRAF6 degradation, which mediates the continuous inflammation in tumors.