Journal of Biological Chemistry

The cyclin-dependent kinase inhibitor p27 facilitates chemosensitivity by promoting ferroptosis in epithelial ovarian cancer

Platinum-based chemotherapy remains the cornerstone of the treatment of epithelial ovarian cancer (EOC); however, platinum resistance is a major cause of tumor recurrence and mortality in EOC patients. This study reports the mechanism by which EOC cells develop resistance to cisplatin by inhibiting the ferroptosis. Immunohistochemical analysis of human EOC tissues revealed that low p27 expression significantly correlated with poor response to chemotherapy and unfavorable patient prognosis. Functionally, CRISPR/Cas9-mediated p27 KO increased cisplatin resistance in EOC cells in both in vitro and in vivo models. RNA sequencing and functional assays demonstrated that p27 enhanced cisplatin sensitivity by facilitating drug-induced ferroptosis in EOC cells. Mechanistically, luciferase reporter assays demonstrated that p27 enhanced the transcriptional activity of cytochrome b-245 heavy chain, a key positive regulator of ferroptosis. Moreover, we found that the small molecule inhibitor SKPin C1 significantly enhanced cisplatin's antitumor effect by preventing p27 degradation, both in vitro and in vivo. In conclusion, our findings emphasize the critical role of p27 in triggering ferroptosis, thereby sensitizing EOC cells to cisplatin therapy. These results suggest that therapeutic strategies aimed at enhancing p27 levels may represent a promising approach to overcoming chemoresistance in EOC.

Cell fate simulation reveals cancer cell features in the tumor microenvironment

To elucidate the dynamic evolution of cancer cell characteristics within the tumor microenvironment (TME), we developed an integrative approach combining single-cell tracking, cell fate simulation, and 3D TME modeling. We began our investigation by analyzing the spatiotemporal behavior of individual cancer cells in cultured pancreatic (MiaPaCa2) and cervical (HeLa) cancer cell lines, with a focus on the α2-6 sialic acid (α2-6Sia) modification on glycans, which is associated with cell stemness. Our findings revealed that MiaPaCa2 cells exhibited significantly higher levels of α2-6Sia modification, correlating with enhanced reproductive capabilities, whereas HeLa cells showed less prevalence of this modification. To accommodate the in vivo variability of α2-6Sia levels, we employed a cell fate simulation algorithm that digitally generates cell populations based on our observed data while varying the level of sialylation, thereby simulating cell growth patterns. Subsequently, we performed a 3D TME simulation with these deduced cell populations, considering the microenvironment that could impact cancer cell growth. Immune cell landscape information derived from 193 cervical and 172 pancreatic cancer cases was used to estimate the degree of the positive or negative impact. Our analysis suggests that the deduced cells generated based on the characteristics of MiaPaCa2 cells are less influenced by the immune cell landscape within the TME compared to those of HeLa cells, highlighting that the fate of cancer cells is shaped by both the surrounding immune landscape and the intrinsic characteristics of the cancer cells.

SETD7 promotes LC3B methylation and degradation in ovarian cancer

Microtubule-associated protein 1 light chain 3 (LC3) is a key autophagy-related protein involved in regulating autophagosome formation and autophagy activity. Post-translational modifications of LC3 are necessary to modulate its function. However, LC3 protein methylation and its physiological significance have not yet been elucidated. Here, we show that SET domain containing lysine methyltransferase 7 (SETD7) interacts with LC3B, a common isoform of LC3, and methylates LC3B at lysine 51 (K51). SETD7-mediated methylation of LC3B promotes ubiquitination and degradation of LC3B, resulting in reduced autophagosome formation. Furthermore, SETD7 exerts a tumor-promotive function in ovarian cancer (OC) cells in a K51 methylation-dependent manner. Collectively, our data define a novel modification of LC3B and highlight the oncogenic effect of SETD7 via mediating LC3B methylation and degradation.

The BHLHE40‒PPM1F‒AMPK pathway regulates energy metabolism and is associated with the aggressiveness of endometrial cancer

BHLHE40 is a basic helix-loop-helix transcription factor that is involved in multiple cell activities including differentiation, cell cycle, and epithelial-to-mesenchymal transition. While there is growing evidence to support the functions of BHLHE40 in energy metabolism, little is known about the mechanism. In this study, we found that BHLHE40 expression was downregulated in cases of endometrial cancer of higher grade and advanced disease. Knockdown of BHLHE40 in endometrial cancer cells resulted in suppressed oxygen consumption and enhanced extracellular acidification. Suppressed pyruvate dehydrogenase (PDH) activity and enhanced lactated dehydrogenase (LDH) activity were observed in the knockdown cells. Knockdown of BHLHE40 also led to dephosphorylation of AMPKα Thr172 and enhanced phosphorylation of pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1) Ser293 and lactate dehydrogenase A (LDHA) Tyr10. These results suggested that BHLHE40 modulates PDH and LDH activity by regulating the phosphorylation status of PDHA1 and LDHA. We found that BHLHE40 enhanced AMPKα phosphorylation by directly suppressing the transcription of an AMPKα-specific phosphatase, PPM1F. Our immunohistochemical study showed that the expression of BHLHE40, PPM1F, and phosphorylated AMPKα correlated with the prognosis of endometrial cancer patients. Because AMPK is a central regulator of energy metabolism in cancer cells, targeting the BHLHE40‒PPM1F‒AMPK axis may represent a strategy to control cancer development.

Regulatory role for tumor suppressor REST on estrogen receptor (ESR1) expression and leiomyoma pathophysiology

Uterine fibroids, benign tumors of the smooth muscle layer of the uterus, plague approximately 80% of the female population by age 50. While there have been efforts to understand the mechanism behind this pathophysiology, it largely remains unclear. Lack of preclinical animal models that recapitulate aberrant steroid hormone pathways in UL has significantly hampered the development of long-term hormonal therapies for uterine fibroids. In addition, cultured myometrial as well as leiomyoma smooth muscle cells rapidly silence both estrogen receptor alpha (ESR1) and progesterone receptor (PGR) expression through unknown mechanisms, further limiting in vitro mechanistic studies of UL. Previous work by our lab has determined that the loss of REST, a master regulator of epigenetic gene silencing, in leiomyoma results in the upregulation of ESR1 targets and, therefore, estrogen signaling. Using ChIP-PCR, we find that REST is directly associated with the ESR1 genomic locus, playing a role in its epigenetic regulation. ChIP-seq analysis of Rest cKO mouse uterus samples reveals a global role for REST in the regulation of progesterone receptor target genes and highlights alterations in PGR binding within the Esr1 locus. Additionally, we find REST inhibition of ESR1 expression is regulated through the upstream WNT planar cell polarity molecule, PRICKLE1 (PK1). Based on the role of REST in silencing ESR1 expression in cultured myometrial cells, our results support the development of a potential cell culture method to maintain ESR1 expression through REST modulation. Finally, we establish a broad role for REST in epigenetic regulation relevant to leiomyoma pathophysiology.

The constitutively active form of a key cholesterol synthesis enzyme is lipid droplet-localized and upregulated in endometrial cancer tissues

Cholesterol is essential for both normal cell viability and cancer cell proliferation. Aberrant activity of squalene monooxygenase (SM, also known as squalene epoxidase), the rate-limiting enzyme of the committed cholesterol synthesis pathway, is accordingly implicated in a growing list of cancers. We previously reported that hypoxia triggers the truncation of SM to a constitutively active form, thus preserving sterol synthesis during oxygen shortfalls. Here, we show SM truncation is upregulated and correlates with the magnitude of hypoxia in endometrial cancer tissues, supporting the in vivo relevance of our earlier work. To further investigate the pathophysiological consequences of SM truncation, we examined its lipid droplet-localized pool using complementary immunofluorescence and cell fractionation approaches and found that it exclusively comprises the truncated enzyme. This partitioning is facilitated by the loss of an endoplasmic reticulum-embedded region at the SM N terminus, whereas the catalytic domain containing membrane-associated C-terminal helices is spared. Moreover, we determined multiple amphipathic helices contribute to the lipid droplet localization of truncated SM. Taken together, our results expand on the striking differences between the two forms of SM and suggest upregulated truncation may contribute to SM-related oncogenesis.

LncRNA FAM83H-AS1 inhibits ferroptosis of endometrial cancer by promoting DNMT1-mediated CDO1 promoter hypermethylation

Endometrial cancer (EC) is the most prevalent gynecological epithelial malignancy. DNA methylation is a promising cancer biomarker but limited use for detecting EC. We previously found that the level of cysteine dioxygenase 1 (CDO1) promoter methylation was elevated in EC patients through methylomics, but the role and mechanism of CDO1 in EC remained unclear. Here, the methylation level of CDO1 promoter was detected by bisulfite-sequencing PCR and methylation-specific PCR (bisulfite conversion-based PCR methods, which remain the most commonly used techniques for methylation detection). Cells were incubated with erastin (the ferroptosis activator). Cell vitality was measured using the cell counting kit-8 assay. FAM83H-AS1 cellular distribution was analyzed by the fluorescence in situ hybridization assay. Lipid reactive oxygen species level was examined by BODIPY-C11 staining. The interactions between FAM83H-AS1, CDO1, and DNA methyltransferase1 (DNMT1) were analyzed by RNA-binding protein immunoprecipitation or chromatin immunoprecipitation assay. The xenograft mouse model was utilized to test CDO1 and FAM83H-AS1's influence on tumor development in vivo. Results showed that CDO1 was hypermethylated and downregulated in EC. CDO1 knockdown reduced erastin-induced ferroptosis in EC cells. Mechanistically, DNMT1 is a DNA methyltransferase, which can transfer methyl groups to cytosine nucleotides in genomic DNA. Long noncoding RNA FAM83H-AS1 increased CDO1 promoter methylation level and inhibited its expression in EC cells by recruiting DNMT1. CDO1 knockdown or FAM83H-AS1 overexpression promoted EC tumor growth in vivo. Long noncoding RNA FAM83H-AS1 inhibited ferroptosis in EC by recruiting DNMT1 to increase CDO1 promoter methylation level and inhibit its expression.

Tissue transglutaminase activates integrin-linked kinase and β-catenin in ovarian cancer

Ovarian cancer (OC) is the most lethal gynecological cancer. OC cells have high proliferative capacity, are invasive, resist apoptosis, and tumors often display rearrangement of extracellular matrix (ECM) components, contributing to accelerated tumor progression. The multifunctional protein tissue transglutaminase (TG2) is known to be secreted in the tumor microenvironment, where it interacts with fibronectin (FN) and the cell surface receptor integrin β1. However, the mechanistic role of TG2 in cancer cell proliferation is unknown. Here, we demonstrate that TG2 directly interacts with and facilitates the phosphorylation and activation of the integrin effector protein integrin-linked kinase (ILK) at Ser246. We show that TG2 and p-Ser246-ILK form a complex that is detectable in patient-derived OC primary cells grown on FN-coated slides. In addition, we show that coexpression of TGM2 and ILK correlates with poor clinical outcome. Mechanistically, we demonstrate that TG2-mediated ILK activation causes phosphorylation of glycogen synthase kinase-3α/β, allowing β-catenin nuclear translocation and transcriptional activity. Furthermore, inhibition of TG2 and ILK using small molecules, neutralizing antibodies, or shRNA-mediated knockdown blocks cell adhesion to the FN matrix, as well as the Wnt receptor response to the Wnt-3A ligand, and ultimately, cell adhesion, growth, and migration. In conclusion, we demonstrate that TG2 directly interacts with and activates ILK in OC cells and tumors and define a new mechanism that links ECM cues with β-catenin signaling in OC. These results suggest a central role of TG2-FN-integrin clusters in ECM rearrangement and indicate that downstream effector ILK may represent a potential new therapeutic target in OC.

Magnesium-dependent-protein phosphatase 1B regulates the protein arginine methyltransferase 5 through the modulation of myosin phosphatase

Dysregulation of the expression levels and the activity of kinases/phosphatases is an intrinsic hallmark of tumor transformation and progression, as either as a primary cause or consequence. The myosin phosphatase (MP)/protein arginine methyltransferase 5 (PRMT5)/histone (H4) pathway is an oncogenic signaling pathway downregulating the gene expression of tumor suppressors. However, the upstream regulators of the pathway are unknown. We show that the Mg

CBX2 promotes cervical cancer cell proliferation and resistance to DNA-damaging treatment via maintaining cancer stemness

Cervical cancer is the fourth most common malignancy and the fourth leading cause of cancer-related death among women. Advanced stages and resistance to treatment in cervical cancer induce cancer-related deaths. Although epigenetics has been known to play a vital role in tumor progression and resistance, the function of epigenetic regulators in cervical cancer is an area of investigation. In this study, we focused on an epigenetic regulator, polycomb repressor complex 1 in cervical cancer. Through bioinformatics analysis and immunochemistry, we subsequently identified chromobox 2CBX2), the deregulated subunit of polycomb repressor complex 1, which is upregulated in cervical cancer and associated with poor prognosis and unfavorable clinicopathological characteristics. We provided functional evidence demonstrating that CBX2 promoted cervical cancer cell proliferation. Furthermore, CBX2 exhibited an antiapoptotic effect, which induced resistance to cisplatin and ionizing radiation in cervical cancer cells. Moreover, CBX2 was involved in maintaining cancer stemness. These findings suggest that CBX2 plays an important role in cervical cancer progression and resistance to treatment, and may serve as a potential biomarker for prognosis and resistance as well as a potential therapeutic target.

Development of the nonreceptor tyrosine kinase FER-targeting PROTACs as a potential strategy for antagonizing ovarian cancer cell motility and invasiveness

Aberrant overexpression of nonreceptor tyrosine kinase FER (Fps/Fes Related) has been reported in various ovarian carcinoma-derived tumor cells and is a poor prognosis factor for patient survival. It plays an essential role in tumor cell migration and invasion, acting concurrently in both kinase-dependent and -independent manners, which is not easily suppressed by conventional enzymatic inhibitors. Nevertheless, the PROteolysis-TArgeting Chimera (PROTAC) technology offers superior efficacy over traditional activity-based inhibitors by simultaneously targeting enzymatic and scaffold functions. Hence in this study, we report the development of two PROTAC compounds that promote robust FER degradation in a cereblon-dependent manner. Both PROTAC degraders outperform a Food and Drug Administration-approved drug, brigatinib, in ovarian cancer cell motility suppression. Importantly, these PROTAC compounds also degrade multiple oncogenic FER fusion proteins identified in human tumor samples. These results lay an experimental foundation to apply the PROTAC strategy to antagonize cell motility and invasiveness in ovarian and other types of cancers with aberrant expression of FER kinase and highlight PROTACs as a superior strategy for targeting proteins with multiple tumor-promoting functions.

RAD54B mutations enhance the sensitivity of ovarian cancer cells to poly(ADP-ribose) polymerase (PARP) inhibitors

Synthetic lethal targeting of homologous recombination (HR)-deficient ovarian cancers (OvCas) with poly(ADP-ribose) polymerase inhibitors (PARPis) has attracted considerable attention. Olaparib was the first PARPi approved by the Food and Drug Administration, offering significant clinical benefits in BRCA1/2-deficient OvCas. However, only approximately 20% of OvCa patients harbor BRCA1/2 mutations. Given the shared roles that BRCA1/2 have with other HR regulators, alterations in HR genes may also contribute to "BRCAness profiles" in OvCas. RAD54B has been considered a key player in HR repair, although its roles and therapeutic potential in cancers need further investigation. Here, we identified 22 frequently mutated HR genes by whole-exome sequencing of OvCa tissues from 82 patients. To our surprise, 7.3% of patients were found to harbor mutations of RAD54B, the third-highest mutated gene among patients. We determined that RAD54B-mutated tumor tissues harbored more DNA double-strand breaks than normal tissues. Additionally, we found that RAD54B knockdown inhibited HR repair, enhanced sensitivities of OvCa cells with increased DNA double-strand breaks to olaparib, and induced apoptosis. Enhanced inhibitory effects of olaparib on the growth of ES2 xenograft tumors were further demonstrated by RAD54B knockdown. Finally, we show that restoration with wildtype RAD54B rather than RAD54B

Phosphorylation of mixed lineage kinase MLK3 by cyclin-dependent kinases CDK1 and CDK2 controls ovarian cancer cell division

Mixed lineage kinase 3 (MLK3) is a serine/threonine mitogen-activated protein kinase kinase kinase that promotes the activation of multiple mitogen-activated protein kinase pathways and is required for invasion and proliferation of ovarian cancer cells. Inhibition of MLK activity causes G2/M arrest in HeLa cells; however, the regulation of MLK3 during ovarian cancer cell cycle progression is not known. Here, we found that MLK3 is phosphorylated in mitosis and that inhibition of cyclin-dependent kinase 1 (CDK1) prevented MLK3 phosphorylation. In addition, we observed that c-Jun N-terminal kinase, a downstream target of MLK3 and a direct target of MKK4 (SEK1), was activated in G2 phase when CDK2 activity is increased and then inactivated at the beginning of mitosis concurrent with the increase in CDK1 and MLK3 phosphorylation. Using in vitro kinase assays and phosphomutants, we determined that CDK1 phosphorylates MLK3 on Ser548 and decreases MLK3 activity during mitosis, whereas CDK2 phosphorylates MLK3 on Ser770 and increases MLK3 activity during G1/S and G2 phases. We also found that MLK3 inhibition causes a reduction in cell proliferation and a cell cycle arrest in ovarian cancer cells, suggesting that MLK3 is required for ovarian cancer cell cycle progression. Taken together, our results suggest that phosphorylation of MLK3 by CDK1 and CDK2 is important for the regulation of MLK3 and c-Jun N-terminal kinase activities during G1/S, G2, and M phases in ovarian cancer cell division.

Comprehensive analysis of consensus molecular subtypes for ovarian cancer from bulk to single-cell perspectives

Molecular subtypes play a pivotal role in guiding preclinical and clinical risk assessment and treatment strategies in cancer. In this study, we extracted whole-tissue transcriptomic data from 1987 ovarian cancer patients spanning 26 independent Gene Expression Omnibus cohorts. A total of four consensus subtypes (C1-C4) were identified, notably, subtype C1 samples exhibited a poor prognosis and higher M2 macrophages infiltration, whereas subtype C2 samples demonstrated the best prognosis and higher CD4 resting T cells infiltration. Additionally, we characterized cancer- and stromal-specific gene expression profiles, and conducted an analysis of ligand-receptor interactions within these compartments. Based on cancer compartment, subtype-specific interactions as well as gene signatures for each molecular subtype were identified. Leveraging single-cell transcriptomic data, we delineated malignant epithelial cells with four molecular subtypes and observed an increase in C1 cell proportions from primary to relapse to metastasis stages, with a corresponding decrease in C2 cell proportions. Furthermore, we investigated subtype-specific interaction with T cells through integrated analysis of bulk and single-cell datasets. Finally, we developed a robust ten-gene risk model based on subtype gene signatures for prognostic evaluation in ovarian cancer, demonstrating its efficacy across independent datasets. In summary, this study systematically explored ovarian cancer molecular subtypes and provided a framework for other cancer types.

A peptide CORO1C-47aa encoded by the circular noncoding RNA circ-0000437 functions as a negative regulator in endometrium tumor angiogenesis

Circular RNAs (circRNAs) are a novel class of widespread noncoding RNAs that regulate gene expression in mammals. Recent studies demonstrate that functional peptides can be encoded by short open reading frames in noncoding RNAs, including circRNAs. However, the role of circRNAs in various physiological and pathological states, such as cancer, is not well understood. In this study, through deep RNA sequencing on human endometrial cancer (EC) samples and their paired adjacent normal tissues, we uncovered that the circRNA hsa-circ-0000437 is significantly reduced in EC compared with matched paracancerous tissue. The hsa-circ-0000437 contains a short open reading frame encoding a functional peptide termed CORO1C-47aa. Overexpression of CORO1C-47aa is capable of inhibiting angiogenesis at the initiation stage by suppressing endothelial cell proliferation, migration, and differentiation through competition with transcription factor TACC3 to bind to ARNT and suppress VEGF. CORO1C-47aa directly bound to ARNT through the PAS-B domain, and blocking the association between ARNT and TACC3, which led to reduced expression of VEGF, ultimately lead to reduced angiogenesis. The antitumor effects of CORO1C-47aa on EC progression suggest that CORO1C-47aa has potential value in anticarcinoma therapies and warrants further investigation.

ZNF280A and ACRV1 enhance aerobic glycolysis and drive ovarian cancer progression via the PI3K/AKT signaling pathway

Ovarian cancer (OC) remains a leading cause of gynecological cancer-related mortality, largely due to metabolic reprogramming and aggressive progression. Zinc finger protein 280A (ZNF280A), a poorly characterized transcriptional regulator, has recently been implicated in tumorigenesis, but its mechanistic role in OC remains undefined. Here, we identify ZNF280A as an oncogenic driver that promotes OC progression through transcriptional regulation of acrosomal vesicle protein 1 (ACRV1) and activation of the PI3K/AKT signaling pathway. ZNF280A expression was markedly elevated in OC tissues and cell lines and correlated with advanced clinicopathologic features and poor patient survival. Functional assays revealed that ZNF280A knockdown inhibited OC cell proliferation, migration, and tumorigenesis while inducing apoptosis both in vitro and in vivo. Mechanistically, ZNF280A enhanced ACRV1 transcription by interacting with the transcription factor CUX2, thereby facilitating its recruitment to the ACRV1 promoter. Elevated ZNF280A or ACRV1 expression activated PI3K/AKT signaling and increased glycolytic enzyme expression (PKM2 and LDHA), glucose uptake, lactate production, ATP generation, and extracellular acidification rate, whereas pharmacological inhibition of AKT or glycolysis abrogated these effects. Collectively, our findings establish ZNF280A as a key regulator of metabolic reprogramming in OC through the CUX2-ACRV1-PI3K/AKT axis, highlighting this pathway as a potential therapeutic target in ovarian cancer.

5hmC enhances PARP trapping and restores PARP inhibitor sensitivity in chemoresistant BRCA1/2-deficient cells

Mutations in BRCA1 and BRCA2 genes are the leading cause of hereditary breast and ovarian cancer. BRCA1/2-mutant cells are defective in repairing damaged DNA by homologous recombination and are characterized by hypersensitivity to PARP inhibitors. PARP inhibitors can trap PARP proteins on the chromatin, a mechanism that can contribute to the death of BRCA1/2-deficient cells. The FDA has approved multiple PARP inhibitors for the treatment of metastatic breast and ovarian cancers, yet despite the success of PARP inhibitors in treating BRCA1/2-mutant cancers, drug resistance is a major challenge. Here, we report that 5hmC enhances PARP1 trapping on the chromatin in olaparib-treated cells. Elevated PARP trapping generates replication gaps, leading to the restoration of PARP inhibitor sensitivity in chemoresistant BRCA1/2-deficient cells. Our findings suggest that combining 5hmC with olaparib can restore the sensitivity of chemoresistant BRCA1/2-deficient cells.

Immune checkpoint protein PD-L1 promotes transcription of angiogenic and oncogenic proteins IL-8, Bcl3, and STAT1 in ovarian cancer cells

Immunotherapies blocking cell surface signaling of the immune checkpoint PD-L1 have shown great promise in several cancers, but the results have been disappointing in ovarian cancer (OC). One of the main underlying mechanisms likely consists of the cell-intrinsic intracellular functions of PD-L1, which are incompletely understood. The expression of PD-L1 in OC cells is induced by interferon-γ (IFNγ), a pleiotropic cytokine produced in response to chemotherapy or immune checkpoint blockade. We have recently shown that IFNγ induces expression of the proto-oncogene Bcl3, the proangiogenic chemokine interleukin-8 (IL-8)-CXCL8, and the transcription factor STAT1, resulting in increased OC cell proliferation and migration. Here, we report that IFNγ-induced expression of PD-L1 results in PD-L1 recruitment to IL-8, Bcl3, and STAT1 promoters. The occupancy of PD-L1 at IL-8, Bcl3, and STAT1 promoters is associated with increased histone acetylation and RNA polymerase II recruitment to these promoters. Suppression of IFNγ-induced PD-L1 decreases the expression of IL-8, Bcl3, and PD-L1 and increases apoptosis in OC cells. Together, these findings demonstrate that PD-L1 promotes transcription of IL-8, Bcl3, and STAT1, thus providing a novel function of PD-L1 in cancer cells, and suggesting that the increased IL-8, Bcl3, and STAT1 expression mediated by PD-L1 might contribute to the limited effectiveness of cancer immunotherapies targeting the surface expression of PD-L1 in OC.

FDX2, an iron-sulfur cluster assembly factor, is essential to prevent cellular senescence, apoptosis or ferroptosis of ovarian cancer cells

Recent studies reveal that biosynthesis of iron-sulfur clusters (Fe-Ss) is essential for cell proliferation, including that of cancer cells. Nonetheless, it remains unclear how Fe-S biosynthesis functions in cell proliferation/survival. Here, we report that proper Fe-S biosynthesis is essential to prevent cellular senescence, apoptosis, or ferroptosis, depending on cell context. To assess these outcomes in cancer, we developed an ovarian cancer line with conditional KO of FDX2, a component of the core Fe-S assembly complex. FDX2 loss induced global downregulation of Fe-S-containing proteins and Fe

Dysregulation of hsa-miR-34a and hsa-miR-449a leads to overexpression of PACS-1 and loss of DNA damage response (DDR) in cervical cancer

We have observed overexpression of PACS-1, a cytosolic sorting protein in primary cervical tumors. Absence of exonic mutations and overexpression at the RNA level suggested a transcriptional and/or posttranscriptional regulation. University of California Santa Cruz genome browser analysis of PACS-1 micro RNAs (miR), revealed two 8-base target sequences at the 3' terminus for hsa-miR-34a and hsa-miR-449a. Quantitative RT-PCR and Northern blotting studies showed reduced or loss of expression of the two microRNAs in cervical cancer cell lines and primary tumors, indicating dysregulation of these two microRNAs in cervical cancer. Loss of PACS-1 with siRNA or exogenous expression of hsa-miR-34a or hsa-miR-449a in HeLa and SiHa cervical cancer cell lines resulted in DNA damage response, S-phase cell cycle arrest, and reduction in cell growth. Furthermore, the siRNA studies showed that loss of PACS-1 expression was accompanied by increased nuclear γH2AX expression, Lys