Excessive activation of IL-33/ST2 in cancer-associated fibroblasts promotes invasion and metastasis in ovarian cancer

Ovarian cancer is highly prevalent and has high mortality rates due to metastasis and relapse. The cross communication between cancer-associated fibroblasts (CAFs) and cancer-associated macrophages (CAMs) in the ovarian tumor microenvironment leads to cancer cell invasion and metastasis. However, the role of overproduction of IL-33/ST2 in the CAFs of ovarian cancer is still unclear. The expression of IL-33, ST2, apoptosis-related proteins and epithelial-mesenchymal transition (EMT) markers was measured by western blotting. Primary normal fibroblasts and CAFs from ovarian cancerous tissue were isolated and cultured in vitro, and the medium was used to stimulate blood-derived monocytes. Flow cytometry analysis was used to detect the frequency of M2-like macrophages in blood-derived monocytes from patients with ovarian cancer. Cell invasion were evaluated using Transwell assays. A xenograft model was used to study tumor growth in ST2-knockout and wild-type NOD-SCID mice. The results demonstrated higher expression of IL-33 and ST2 in carcinoma tissues compared with in para-carcinoma tissues, and there was a survival improvement associated with elevated IL-33. IL-33 and culture supernatants from CAFs, rather than normal ovarian fibroblasts, led to a higher expression of M2 macrophage marker genes in human blood-derived monocytes. Invasion and migration were aggravated in COC1 cells co-cultured with CAF-induced CAMs, and the EMT marker genes were upregulated. It was reported that EMT marker genes were downregulated and tumor volumes were significantly reduced in ST2-deficient mice. Overall, the IL-33/ST2 axis in ovarian cancer might integrate IL-33-expressing CAFs with M2 type-like CAMs, which aggravated invasion and metastasis by promoting EMT.     

Deubiquitinase OTUD6A promotes proliferation of cancer cells via regulating Drp1 stability and mitochondrial fission

Dynamin‐related protein 1 (Drp1) is a cytosolic protein responsible for mitochondrial fission and is essential in the initiation and development of several human diseases, including cancer. However, the regulation of Drp1, especially of its ubiquitination, remains unclear. In this study, we report that the ovarian tumor‐associated protease deubiquitinase 6A (OTUD6A) deubiquitylates and stabilizes Drp1, thereby facilitating regulation of mitochondrial morphology and tumorigenesis. OTUD6A is upregulated in human patients with colorectal cancer. The depletion of OTUD6A leads to lower Drp1 levels and suppressed mitochondrial fission, and the affected cells are consequently less prone to tumorigenesis. Conversely, the overexpression of OTUD6A increases Drp1 levels and its protein half‐life and enhances cancer cell growth. Therefore, our results reveal a novel upstream protein of Drp1, and its role in tumorigenesis that is played, in part, through the activation of mitochondrial fission mediated by Drp1.

Abbreviations

Drp1

dynamin‐related protein 1

DUBs

deubiquitinases

His‐ub

His‐ubiquitin

IB

immunoblot

IHC

immunohistochemistry

IP

immunoprecipitation

MARCH5

membrane‐associated ring‐CH‐type finger 5

Mfn1

mitofusin 1

Mfn2

mitofusin 2

NIK

NF‐κB‐inducing kinase

Opa1

optic atrophy 1

OTUs

ovarian tumor‐associated proteases

OTUD6A

ovarian tumor‐associated protease deubiquitinase 6A

     

Role of the IL-33/ST2 receptor axis in ovarian cancer progression

Ovarian cancer remains a significant health problem for women in the world due to its diagnosis at advanced stages of disease and the high mortality rate of patients. To date, ovarian cancer is frequently treated with tumor reduction surgery followed by platinum/paclitaxel-based chemotherapy; however, most patients eventually develop relapsed disease. The mRNA expression levels of interleukin-33 (IL-33) and the suppressor of tumorigenicity 2 (ST2) receptor are significantly upregulated in ovarian cancer tissues and metastatic tumor lesions. In addition, IL-33 and ST2 expression has been associated with a poor overall survival in patients with epithelial ovarian cancer. The IL-33 receptor ST2 is expressed as both a membrane-anchored receptor (ST2L) activated by IL-33, and as a soluble variant that exhibits anti-inflammatory properties. In the present review, the functions of the IL-33/ST2L axis in cells and their aberrant expression levels in ovarian cancer were discussed. In addition, targeting their expression as a novel strategy for the control of ovarian cancer progression was emphasized.     

CircATRNL1 activates Smad4 signaling to inhibit angiogenesis and ovarian cancer metastasis via miR‐378

Ovarian cancer is one of the most frequent carcinomas in females, and the occurrence rate is still rising despite many advances made. The pathogenesis of ovarian cancer remains greatly unclear. Here, we investigated the mechanisms of ovarian cancer, with the focus on circATRNL1. Human ovarian cancer tissues and cell lines were used to examine levels of circATRNL1, miR‐378, Smad4, AKT, and other proliferation‐related and migration‐related proteins. Cellular assays were used to determine cancer cell proliferation, invasion, migration, apoptosis, and angiogenesis. We validated the interactions of circATRNL1/miR‐378 and miR‐378/Smad4, and a mouse tumor xenograft model was employed to assess the effect of circATRNL1 on tumor growth and metastasis in vivo. We found that circATRNL1 was decreased while miR‐378 was increased in human ovarian cancer tissues and cells. circATRNL1 bound to miR‐378 while miR‐378 directly targeted Smad4. Overexpression of circATRNL1 or knockdown of miR‐378 suppressed angiogenesis and ovarian cancer cell proliferation, invasion, and migration via decreasing proliferation‐ and migration‐related proteins via miR‐378 or Smad4, respectively. Overexpression of circATRNL1 restrained ovarian cancer growth and abdominal metastasis in vivo. Our findings indicate that circATRNL1 acts as a miR‐378 sponge to active Smad4 signaling and suppresses angiogenesis and ovarian cancer metastasis.     

Epigenetic silencing of microRNA-199b-5p is associated with acquired chemoresistance via activation of JAG1-Notch1 signaling in ovarian cancer

Epithelial ovarian cancer is a highly lethal and aggressive gynecological malignancy. The high mortality rate is due in part to the fact that many advanced cancer patients become refractory to current chemotherapeutic agents, leading to tumor recurrence and death. However, the underlying mechanisms leading to chemoresistance remain obscure. Here, we report that the loss of miR-199b-5p due to progressive epigenetic silencing leads to the activation of the JAG1-mediated Notch1 signaling cascade, thereby leading to the development of acquired chemoresistance in ovarian cancer. Using miRCURY LNA™ microRNA array and Q-PCR analyses of two pairs of cisplatin-sensitive and –resistant ovarian cancer cell lines, we identified miR-199b-5p as significantly down-regulated in cisplatin-resistant ovarian cancer cells and confirmed that miR-199b-5p is clinically associated with advanced and poor survival ovarian cancers. Interestingly, the loss of miR-199b-5p could be restored by 5-Aza-dC-mediated demethylation, and methylated specific PCR (MS-PCR), bisulfite-sequencing and pyrosequencing revealed that the promoter region of miR-199b-5p was hypermethylated. Computational and mechanistic analyses identified JAG1 as a primary target of miR-199b-5p. Notably, the reduced expression of miR-199b-5p was found to be inversely correlated with the increased expression of JAG1 using an ovarian cancer tissue array. Enforced expression of miR-199b-5p sensitized ovarian cancer cells to cisplatin-induced cytotoxicity both in vitro and in vivo. Conversely, re-expression of miR-199b-5p and siRNA-mediated JAG1 knockdown or treatment with Notch specific inhibitor γ-secretase (GSI) attenuated JAG1-Notch1 signaling activity, thereby enhancing cisplatin-mediated cell cytotoxicity. Taken together, our study suggests that the epigenetic silencing of miR-199b-5p during tumor progression is significantly associated with acquired chemoresistance in ovarian cancer through the activation of JAG1-Notch1 signaling.     

Metadherin exon 11 skipping variant enhances metastatic spread of ovarian cancer

Metastatic ovarian cancer has a dismal prognosis and current chemotherapeutic approaches have very limited success. Metadherin (MTDH) is expressed in human ovarian cancer tissue and its expression inversely correlates with patients overall survival. Consistent with these studies, we observed MTDH expression in tissue specimens of FIGO Stage III ovarian carcinomas (72/83 cases). However, we also observed this in normal human ovarian epithelial (OE) cells, which raised the question of whether MTDH‐variants with functional differences exist. We identified a novel MTDH exon 11 skipping variant (MTDHdel) which was seen at higher levels in ovarian cancer compared to benign OE cells. We analyzed MTDH‐binding partner interactions and found that 12 members of the small ribosomal subunit and several mRNA binding proteins bound stronger to MTDHdel than to wildtype MTDH which indicates differential effects on gene translation. Knockdown of MTDH in ovarian cancer cells reduced the amount of distant metastases and improved the survival of ovarian cancer‐bearing mice. Selective overexpression of the MTDHdel enhanced murine and human ovarian cancer progression and caused a malignant phenotype in originally benign human OE cells. MTDHdel was detectable in microdissected ovarian cancer cells of some human tissue specimens of ovarian carcinomas. In summary, we have identified a novel MTDH exon 11 skipping variant that shows enhanced binding to small ribosomal subunit members and that caused reduced overall survival of ovarian cancer bearing mice. Based on the findings in the murine system and in human tissues, MTDHdel must be considered a major promalignant factor for ovarian cancer.     

Induction of metastatic potential by TrkB via activation of IL6/JAK2/STAT3 and PI3K/AKT signaling in breast cancer

In metastatic breast cancers, the acquisition of metastatic ability, which leads to clinically incurable disease and poor survival, has been associated with acquisition of epithelial-mesenchymal transition (EMT) program and self-renewing trait (CSCs) via activation of PI3K/AKT and IL6/JAK2/STAT3 signaling pathways. We found that TrkB is a key regulator of PI3K/AKT and JAK/STAT signal pathway-mediated tumor metastasis and EMT program. Here, we demonstrated that TrkB activates AKT by directly binding to c-Src, leading to increased proliferation. Also, TrkB increases Twist-1 and Twist-2 expression through activation of JAK2/STAT3 by inducing c-Src-JAK2 complex formation. Furthermore, TrkB in the absence of c-Src binds directly to JAK2 and inhibits SOCS3-mediated JAK2 degradation, resulting in increased total JAK2 and STAT3 levels, which subsequently leads to JAK2/STAT3 activation and Twist-1 upregulation. Additionally, activation of the JAK2/STAT3 pathway via induction of IL-6 secretion by TrkB enables induction of activation of the EMT program via induction of STAT3 nuclear translocation. These observations suggest that TrkB is a promising target for future intervention strategies to prevent tumor metastasis, EMT program and self-renewing trait in breast cancer.     

SHP2 介导IL-6 促进乳腺癌细胞侵袭作用机制的研究*

目的：探讨非受体型酪氨酸磷酸酶SHP 2 介导白细胞介素- 6（interleukin- 6 ,IL- 6）促进人乳腺癌细胞侵袭的作用,以及相应的分子机制。方法：利用外源性重组IL- 6 处理人乳腺癌细胞T 47D ,采用表达IL- 6 的慢病毒感染T 47D 细胞使其内源性表达IL- 6,观察细胞的形态学改变情况,分析细胞迁移和侵袭能力的变化。采用小RNA 干扰的方法下调IL- 6 信号通路中关键分子SHP 2 的表达,观察其表达下降对IL- 6 促进乳腺癌细胞侵袭能力的影响,同时采用Westernblot方法检测Erk1/ 2 磷酸化变化。结果：上调IL- 6 在乳腺癌细胞中的表达显著促进乳腺癌细胞的迁移和侵袭能力,且细胞发生由上皮形态向类成纤维细胞形态的变化,同时伴随着上皮标志性蛋白E-cadherin 表达下调和间质标志Vimentin 表达上调。下调SHP 2 的表达明显抑制IL- 6 诱导乳腺癌细胞的上皮间质转化（epithelialmesenchymaltransition,EMT ）和侵袭能力,同时伴随着细胞内Erk1/ 2 磷酸化水平的下降。结论：SHP 2 通过介导IL- 6 诱导的EMT 促进乳腺癌细胞的迁移和侵袭能力。     

PRRX1 promotes colorectal cancer stemness and chemoresistance via the JAK2/STAT3 axis by targeting IL-6

BackgroundStemness acquirement is one of the hallmarks of cancer and the major reason for the chemoresistance and poor prognosis of colorectal cancer (CRC). Previous research has revealed the stimulatory role of paired related homeobox 1 (PRRX1) on CRC metastasis. However, the role of PRRX1 in stemness acquirement and chemoresistance of CRC is still not clear.MethodsA retrospective cohort study was performed to investigate the relationship between PRRX1 expression and multiple clinicopathological characteristics of CRC patients. The functional effects of PRRX1 on stemness and chemoresistance of CRC cells were validated by in vitro and in vivo assays. Gene set enrichment analysis (GSEA) and JASPAR software were performed to predict the underlying mechanisms. Enzyme-linked immunosorbent assay (ELISA), Western blot, immunofluorescence, and dual-luciferase reporter assays were used to confirm the PRRX1-mediated signaling and its downstream factors.ResultsThe expression of PRRX1 was up-regulated in CRC tissues and cell lines compared to normal epithelial tissues and cell lines. High expression of PRRX1 was tightly associated with the metastasis, chemoresistance, and poor prognosis of CRC patients. Additionally, PRRX1 significantly promoted the proliferation, viability, stemness, and chemoresistance of CRC cells, as well as the activation of the interleukin-6 (IL-6)/JAK2/STAT3 axis. Inhibiting the expression of IL-6 dramatically eliminated the effects of PRRX1 on CRC cell stemness and chemoresistance.ConclusionsPRRX1 plays a vital role in the stemness and chemoresistance of CRC cells via JAK2/STAT3 signaling by targeting IL-6. Further, PRRX1 may be a valid biomarker for predicting the effect of chemotherapy and prognosis of CRC patients.     

Overexpression of HE4 (human epididymis protein 4) enhances proliferation,invasion and metastasis of ovarian cancer

Overexpression of Human epididymis protein 4 (HE4) related with a role in ovarian cancer tumorigenesis while little is known about the molecular mechanism alteration by HE4 up regulation. Here we reported that overexpressed HE4 promoted ovarian cancer cells proliferation, invasion and metastasis. Furthermore, human whole genome gene expression profile microarrays revealed that 231 differentially expressed genes (DEGs) were altered in response to HE4, in which MAPK signaling, ECM receptor, cell cycle, steroid biosynthesis pathways were involved. The findings suggested that overexpressed HE4 played an important role in ovarian cancer progression and metastasis and that HE4 has the potential to serve as a novel therapeutic target for ovarian cancer.     

结直肠癌细胞IL-4/Stat6信号传导活性与调节基因差异性表达相关性研究

目的:IL-4介导的Stat6信号传导活性在人细胞之间有差异,称为Stat6活化表型。旨在探讨Stat6活化表型及其产生的分子学基础。方法:结直肠癌细胞株HT-29与Caco-2的Stat6活化表型用EMSA半定量法测定。Stat6通路调节因子基因水平的表达用RT-PCR法检测。蛋白水平的表达用Western blotting法检测。结果:EMSA分析表明,HT-29为高活化表型(Stat6high)而Caco-2为零活化表型(Stat6null)。RT-PCR分析显示,与Stat6highHT-29比较,Stat6nullCaco-2癌细胞高表达负调节基因SOCS1和SHP1,而低表达正调节因子PP2A催化亚单位编码基因PP2CA和PP2CB。Westernblotting分析法证实Caco-2癌细胞高表达SOCS1和SHP1蛋白。结论:Stat6通路正、负调节基因的表达失衡可能是产生不同Stat6活化表型的分子机制之一。     

结直肠癌细胞IL-4／Stat6信号传导活性与调节基因差异性表达相关性研究

目的：IL-4介导的Star6信号传导活性在人细胞之间有差异，称为Stat6活化表型。旨在探讨Stat6活化表型及其产生的分子学基础。方法：结直肠癌细胞株HT-29与Caco-2的Star6活化表型用EMSA半定量法测定。Stat6通路调节因子基因水平的表达用RT-PCR法检测。蛋白水平的表达用Western blotting法检测。结果：EMSA分析表明，HT29为高活化表型（Star6^high）而Caco2为零活化表型（Star6^null）。RT-PCR分析显示，与Star6^high HT-29比较，Star6^null Caco-2癌细胞高表达负调节基因SOCS1和SHP1，而低表达正调节因子PP2A催化亚单位编码基因PP2CA和PP2CB。Westernb lotting分析法证实Caco-2癌细胞高表达SOCS1和SHP1蛋白。结论：Star6通路正、负调节基因的表达失衡可能是产生不同Star6活化表型的分子机制之一。     

BCAT1 expression associates with ovarian cancer progression: possible implications in altered disease metabolism

Previously, we have identified the branched chain amino-acid transaminase 1 (BCAT1) gene as notably hypomethylated in low-malignant potential (LMP) and high-grade (HG) serous epithelial ovarian tumors, compared to normal ovarian tissues. Here we show that BCAT1 is strongly overexpressed in both LMP and HG serous epithelial ovarian tumors, which probably correlates with its hypomethylated status. Knockdown of the BCAT1 expression in epithelial ovarian cancer (EOC) cells led to sharp decrease of cell proliferation, migration and invasion and inhibited cell cycle progression. BCAT1 silencing was associated with the suppression of numerous genes and pathways known previously to be implicated in ovarian tumorigenesis, and the induction of some tumor suppressor genes (TSGs). Moreover, BCAT1 suppression resulted in downregulation of numerous genes implicated in lipid production and protein synthesis, suggesting its important role in controlling EOC metabolism. Further metabolomic analyses were indicative for significant depletion of most amino acids and different phospho- and sphingolipids following BCAT1 knockdown. Finally, BCAT1 suppression led to significantly prolonged survival time in xenograft model of advanced peritoneal EOC. Taken together, our findings provide new insights about the functional role of BCAT1 in ovarian carcinogenesis and identify this transaminase as a novel EOC biomarker and putative EOC therapeutic target.     

Loss of HSulf‐1 expression enhances tumorigenicity by inhibiting Bim expression in ovarian cancer

The expression of human Sulfatase1 (HSulf‐1) is downregulated in the majority of primary ovarian cancer tumors, but the functional consequence of this downregulation remains unclear. Using two different shRNAs (Sh1 and Sh2), HSulf‐1 expression was stably downregulated in ovarian cancer OV202 cells. We found that HSulf‐1‐deficient OV202 Sh1 and Sh2 cells formed colonies in soft agar. In contrast, nontargeting control (NTC) shRNA‐transduced OV202 cells did not form any colonies. Moreover, subcutaneous injection of OV202 HSulf‐1‐deficient cells resulted in tumor formation in nude mice, whereas OV202 NTC cells did not. Also, ectopic expression of HSulf‐1 in ovarian cancer SKOV3 cells significantly suppressed tumor growth in nude mice. Here, we show that HSulf‐1‐deficient OV202 cells have markedly decreased expression of proapoptotic Bim protein, which can be rescued by restoring HSulf‐1 expression in OV202 Sh1 cells. Enhanced expression of HSulf‐1 in HSulf‐1‐deficient SKOV3 cells resulted in increased Bim expression. Decreased Bim levels after loss of HSulf‐1 were due to increased p‐ERK, because inhibition of ERK activity with PD98059 resulted in increased Bim expression. However, treatment with a PI3 kinase/AKT inhibitor, LY294002, failed to show any change in Bim protein level. Importantly, rescuing Bim expression in HSulf‐1 knockdown cells significantly retarded tumor growth in nude mice. Collectively, these results suggest that loss of HSulf‐1 expression promotes tumorigenicity in ovarian cancer through regulating Bim expression.     

Combination of nigericin with cisplatin enhances the inhibitory effect of cisplatin on epithelial ovarian cancer metastasis by inhibiting slug expression via the Wnt/β-catenin signalling pathway

Epithelial ovarian cancer (EOC) is the most lethal cancer among female genital tumours. Standard therapies, including postoperative chemotherapy, exhibit high proportions of recurrence and resistance. Novel therapeutic strategies are combined with chemotherapy. Emerging studies have demonstrated that nigericin, an H⁺, K⁺ and Pb²⁺ ionophore, exhibits promising anticancer activity in various types of malignancy, such as colorectal and epithelial ovarian cancer. Our previous study suggested that nigericin could regulate EOC cell proliferation, migration and invasion, and may be a novel chemotherapy candidate for EOC. However, to the best of our knowledge, the effects of combined therapy with cisplatin, and the associated underlying mechanisms, are not yet fully understood. The present study aimed to clarify the effects of combined chemical therapy with nigericin and cisplatin on EOC cells and to reveal its mechanism. Wound healing, Transwell, cell viability and colony formation assays were used to measure the migration, invasion and proliferation of EOC cells. Western blotting was used to detect protein expression. A slug overexpression lentivirus was used to create a slug overexpression model in SK-OV-3 cells. Small interfering RNA was used to knock down slug expression. Nigericin combined with cisplatin enhanced the inhibitory effects of cisplatin on the migration and colony formation of EOC cells. Nigericin also enhanced the inhibitory effects of cisplatin on the expression levels of MMP7, as well as the inhibitory effects of cisplatin on the expression levels of β-catenin and GSK-3β, indicating that nigericin and cisplatin regulated in the Wnt/β-catenin signalling pathway. When slug was knocked down, the effect of nigericin was weakened. Overexpression of slug could repress the inhibitory effect of nigericin on the Wnt/β-catenin signalling pathway. Furthermore, nigericin inhibited slug expression by enhancing its modification through small ubiquitin-like modifiers (SUMOs; referred to as SUMOylation). Overall, the present results demonstrated that nigericin combined with cisplatin might serve as a novel therapeutic strategy in patients with metastatic EOC because the combined therapy had higher effectiveness than single drug use. The underlying mechanism of combined therapy maybe the enhanced inhibitory effect of slug through its nigericin-induced SUMOylation.     

Sphingosine kinase 1 as a potential therapeutic target in epithelial ovarian cancer

Sphingosine kinase 1 (SK1) is over‐expressed in multiple types of human cancer. SK1 has growth‐promoting effects and has been proposed as a potential therapeutic target. We investigated the therapeutic effects of SK1 inhibition in epithelial ovarian carcinoma (EOC). SK1 siRNA or inhibitors were tested in EOC cell lines, including A2780, SKOV3ip1, A2780‐CP20, SKOV3‐TR, ES2 and RMG2. Cells were treated with SK inhibitor or FTY720, and cell proliferation, apoptosis, angiogenesis and invasion were examined by MTT, FACS, ELISA and wound‐healing assays, respectively. In vivo experiments were performed to test the effects of FTY720 on tumor growth in orthotopic mouse xenografts of EOC cell lines A2780 or SKOV3ip1 and a patient‐derived xenograft (PDX) model of clear cell ovarian carcinoma (CCC). Blocking SK1 with siRNA or inhibitors significantly reduced proliferation, angiogenesis and invasion, and increased apoptosis in chemosensitive (A2780 and SKOV3ip1) and chemoresistant (A2780‐CP20, SKOV3‐TR, ES2 and RMG2) EOC cells. SK1 inhibitors also decreased the intracellular enzymatic activity of SK1. Furthermore, FTY720 treatment significantly decreased the in vivo tumor weight in xenograft models of established cell lines (A2780 and SKOV3ip1) and a PDX model for CCC compared to control (p < 0.05). These results support therapeutic targeting of SK1 as a potential new strategy for EOC.     

Antisense blocking of BRCA1 enhances sensitivity to plumbagin but not tamoxifen in BG-1 ovarian cancer cells

Previous studies have shown that reduction in BRCA1 mRNA and protein can result in increased proliferation of BG-1 ovarian cancer cells in both in vitro and in vivo conditions, suggesting that BRCA1 may normally act as a growth inhibitor in these cells. Also, there are other reports that suggest that wild-type BRCA1 protein may repress estrogen receptor (ER) function either directly or indirectly. However, response to antiestrogen drugs in BRCA1-blocked ER-positive ovarian cancer cells has not been reported, and this served as the rationale for this study. We analyzed the effect of tamoxifen, emodin, and plumbagin in BRCA1-blocked ER-positive BG-1 ovarian cancer cells. For all three drugs, BRCA1-blocked cells were more sensitive than the corresponding control cells as assessed by MTT assay; however, only plumbagin showed a statistically significant difference in mean viability (P < 0.05). All three drugs induced loss of mitochondrial membrane potential (DeltaPsi(m)), nuclear condensation, DNA fragmentation, and morphological changes, as observed after 6 h of drug treatment, suggesting apoptosis induction in both BRCA1-blocked and control cells. However, apoptosis induction was greater in BRCA1-blocked cells, the efficacy being in the order of plumbagin > tamoxifen > emodin. The dose of plumbagin needed to kill 50% was 5 microM in the control cells and 2.68 microM for the BRCA1-blocked cells, indicating that the latter was about twofold more sensitive to plumbagin than the wild-type cells. This throws light on the fact that plumbagin may have chemotherapeutic potential as an anticancer agent in BRCA1-mutated ovarian cancer patients.