Epithelial ovarian cancer is a highly lethal gynecological malignancy that is characterized by the early development of disseminated metastasis. Though ovarian cancer has been generally considered to ...preferentially metastasize via direct transcoelomic dissemination instead of the hematogenous route, emerging evidence has indicated that the hematogenous spread of cancer cells plays a larger role in ovarian cancer metastasis than previously thought. Considering the distinctive biology of ovarian cancer, an in-depth understanding of the biological and molecular mechanisms that drive metastasis is critical for developing effective therapeutic strategies against this fatal disease. The recent "cancer stem cell theory" postulates that cancer stem cells are principally responsible for tumor initiation, metastasis, and chemotherapy resistance. Even though the hallmarks of ovarian cancer stem cells have not yet been completely elucidated, metastasized ovarian cancer cells, which have a high degree of chemoresistance, seem to manifest cancer stem cell properties and play a key role during relapse at metastatic sites. Herein, we review our current understanding of the cell-biological mechanisms that regulate ovarian cancer metastasis and chemotherapy resistance, with a pivotal focus on ovarian cancer stem cells, and discuss the potential clinical implications of evolving cancer stem cell research and resultant novel therapeutic approaches.
Metastasis is a complex multistep process that involves critical interactions between cancer cells and a variety of stromal components in the tumor microenvironment, which profoundly influence the ...different aspects of the metastatic cascade and organ tropism of disseminating cancer cells. Ovarian cancer is the most lethal gynecological malignancy and is characterized by peritoneal disseminated metastasis. Evidence has demonstrated that ovarian cancer possesses specific metastatic tropism for the adipose-rich omentum, which has a pivotal role in the creation of the metastatic tumor microenvironment in the intraperitoneal cavity. Considering the distinct biology of ovarian cancer metastasis, the elucidation of the cellular and molecular mechanisms underlying the reciprocal interplay between ovarian cancer cells and surrounding stromal cell types in the adipose-rich metastatic microenvironment will provide further insights into the development of novel therapeutic approaches for patients with advanced ovarian cancer. Herein, we review the biological mechanisms that regulate the highly orchestrated crosstalk between ovarian cancer cells and various cancer-associated stromal cells in the metastatic tumor microenvironment with regard to the omentum by illustrating how different stromal cells concertedly contribute to the development of ovarian cancer metastasis and metastatic tropism for the omentum.
CD44 is an adhesion molecule expressed in cancer stem-like cells. Here, we show that a CD44 variant (CD44v) interacts with xCT, a glutamate-cystine transporter, and controls the intracellular level ...of reduced glutathione (GSH). Human gastrointestinal cancer cells with a high level of CD44 expression showed an enhanced capacity for GSH synthesis and defense against reactive oxygen species (ROS). Ablation of CD44 induced loss of xCT from the cell surface and suppressed tumor growth in a transgenic mouse model of gastric cancer. It also induced activation of p38
MAPK, a downstream target of ROS, and expression of the gene for the cell cycle inhibitor p21
CIP1/WAF1. These findings establish a function for CD44v in regulation of ROS defense and tumor growth.
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► CD44v contributes to the reduction of intracellular reactive oxygen species ► CD44v promotes GSH synthesis by interacting with glutamate-cystine transporter xCT ► Variant 8–10 region is required for CD44v-xCT interaction leading to GSH synthesis ► xCT inhibitor sulfasalazine suppresses CD44-dependent cancer cell expansion in vivo
Peritoneal metastasis is a common mode of spread of ovarian cancer. Despite therapeutic advances, some patients have intractable peritoneal metastasis. Therefore, in-depth characterization of the ...molecular mechanism of peritoneal metastasis is a key imperative. Angiopoietin-like protein 2 (ANGPTL2) is an inflammatory factor which activates NF-κB signaling and plays an important role in the pathogenesis of various inflammatory diseases including cancers, such as lung and breast cancer. In this study, we examined the role of ANGPTL2 in ovarian cancer peritoneal metastasis. We observed no difference of cell proliferation between ANGPTL2-expressing and control cells. In the mouse intraperitoneal xenograft model, formation of peritoneal metastasis by ANGPTL2-expressing cells was significantly decreased compared to control. In the in vitro analysis, the expressions of integrin α5β1, α6, and β4, but not those of αvβ3, α3, α4, and β1, were significantly decreased in ANGPTL2-expressing cells compared to control cells. ANGPTL2-expressing cells showed significantly inhibited adherence to laminin compared to control. In addition, we observed upregulation of anoikis (a form of programmed cell death occurring under an anchorage-independent condition) and significant decrease in the expression of Bcl-2 in ANGPTL2-expressing cells as compared to control cells. These results suggest that ANGPTL2 expression in ovarian cancer cells represses peritoneal metastasis by suppressing anoikis resistance.
•ANGPTL2 expression in ovarian cancer cells repressed peritoneal metastasis.•ANGPTL2 inhibits the expression of Integrin α5β1, α6, and β4.•ANGPTL2 inhibits cell adhesion to laminin.•Anoikis resistance is suppressed in ANGPTL2 expressing ovarian cancer cells.
In cancer metastasis, various environmental stressors attack the disseminating cells. The successful colonization of cancer cells in secondary sites therefore requires the ability of the cells to ...avoid the consequences of such exposure to the stressors. Here we show that orthotopic transplantation of a CD44 variant isoform-expressing (CD44v(+)) subpopulation of 4T1 breast cancer cells, but not that of a CD44v(-) subpopulation, in mice results in efficient lung metastasis accompanied by expansion of stem-like cancer cells. Such metastasis is dependent on the activity of the cystine transporter xCT, and the stability of this protein is controlled by CD44v. We find that epithelial splicing regulatory protein 1 regulates the expression of CD44v, and knockdown of epithelial splicing regulatory protein 1 in CD44v(+) cells results in an isoform switch from CD44v to CD44 standard (CD44s), leading to reduced cell surface expression of xCT and suppression of lung colonization. The epithelial splicing regulatory protein 1-CD44v-xCT axis is thus a potential therapeutic target for the prevention of metastasis.
Background
Epithelial ovarian cancer has a clear predilection for the omentum as the site of metastasis; however, its contribution to clinical outcomes remains unresolved. This study aimed to ...evaluate the prognostic significance and efficacy of chemotherapy in the presence of omental metastasis.
Methods
A retrospective cohort study was performed in 56 patients with stage III–IV ovarian cancer who underwent primary debulking surgery between 2004 and 2018 at Kumamoto University Hospital.
Results
Thirty-six (64.3%) patients were categorized into the omental metastasis-positive group, whereas 20 (35.7%) patients were in the omental metastasis-negative group. The 5-year overall survival rates were 43.4% in the omental metastasis-positive group and 93.8% in the omental metastasis-negative group. Statistically significant differences were observed in overall survival (
p
= 0.002) and progression-free survival (
p
= 0.036) between the omental metastasis-positive and metastasis-negative groups. Notably, multivariate analysis demonstrated that the existence of omental metastasis is an independent risk factor for overall survival in patients with stage III–IV ovarian cancer (hazard ratio 8.90, 95% confidence interval 1.16–69.77;
p
= 0.038). Furthermore, the omental metastasis-positive group had significantly lower overall response rates to chemotherapy for recurrent disease, compared to the omental metastasis-negative group (31.6% vs. 85.7%,
p
= 0.026).
Conclusion
Our present data demonstrated that omental metastasis is closely associated with an unfavorable prognosis due to increased chemoresistance in patients with stage III–IV ovarian cancer. Elucidating the biological mechanism of omental metastasis will shed light on novel therapeutic approaches for the management of advanced ovarian cancer patients.
To obtain baseline data for cervical cancer prevention in Japan, we analyzed human papillomavirus (HPV) data from 5045 Japanese women aged less than 40 years and diagnosed with cervical abnormalities ...at 21 hospitals during 2012‐2017. These included cervical intraepithelial neoplasia grade 1 (CIN1, n = 573), CIN2‐3 (n = 3219), adenocarcinoma in situ (AIS, n = 123), and invasive cervical cancer (ICC, n = 1130). The Roche Linear Array was used for HPV genotyping. The HPV type‐specific relative contributions (RCs) were estimated by adding multiple infections to single types in accordance with proportional weighting attributions. Based on the comparison of type‐specific RCs between CIN1 and CIN2‐3/AIS/ICC (CIN2+), RC ratios were calculated to estimate type‐specific risks for progression to CIN2+. Human papillomavirus DNA was detected in 85.5% of CIN1, 95.7% of CIN2‐3/AIS, and 91.2% of ICC. Multiple infections decreased with disease severity: 42.9% in CIN1, 40.4% in CIN2‐3/AIS, and 23.7% in ICC (P < .0001). The relative risk for progression to CIN2+ was highest for HPV16 (RC ratio 3.78, 95% confidence interval CI 3.01‐4.98), followed by HPV31 (2.51, 1.54‐5.24), HPV18 (2.43, 1.59‐4.32), HPV35 (1.56, 0.43‐8.36), HPV33 (1.01, 0.49‐3.31), HPV52 (0.99, 0.76‐1.33), and HPV58 (0.97, 0.75‐1.32). The relative risk of disease progression was 1.87 (95% CI, 1.71‐2.05) for HPV16/18/31/33/35/45/52/58, but only 0.17 (95% CI, 0.14‐0.22) for HPV39/51/56/59/66/68. Human papillomavirus 16/18/31/33/45/52/58/6/11 included in a 9‐valent vaccine contributed to 89.7% (95% CI, 88.7‐90.7) of CIN2‐3/AIS and 93.8% (95% CI, 92.4‐95.3) of ICC. In conclusion, our data support the Japanese guidelines that recommend discriminating HPV16/18/31/33/35/45/52/58 genotypes for CIN management. The 9‐valent vaccine is estimated to provide over 90% protection against ICC in young Japanese women.
We updated HPV type‐specific risks of and contributions to cervical cancer and precancer in Japan, using a large dataset from young Japanese women with cervical abnormalities. The relative risk for progression to cervical cancer and precancer was the highest for HPV16, followed by HPV31, HPV18, HPV35, HPV33, HPV52 and HPV58. The new 9‐valent vaccine is estimated to provide over 90% protection against invasive cervical cancer among Japanese women up to an age of 40 years.
Cancer stem cells (CSCs) drive tumor initiation and metastasis in several types of human cancer. However, the contribution of ovarian CSCs to peritoneal metastasis remains unresolved. The cell ...adhesion molecule CD44 has been identified as a major marker for CSCs in solid tumors, including epithelial ovarian cancer. CD44 exists as a standard form (CD44s) and also as numerous variant isoforms (CD44v) generated by alternative mRNA splicing. Here we show that disseminated ovarian tumors in the pelvic peritoneum contain highly enriched CD44v6‐positive cancer cells, which drive tumor metastasis and are responsible for tumor resistance to chemotherapy. Clinically, an increased number of CD44v6‐positive cancer cells in primary tumors was associated with a shortened overall survival in stage III–IV ovarian cancer patients. Furthermore, a subpopulation of CD44v6‐positive cancer cells manifested the ability to initiate tumor metastasis in the pelvic peritoneum in an in vivo mouse model, suggesting that CD44v6‐positive cells show the potential to serve as metastasis‐initiating cells. Thus, the peritoneal disseminated metastasis of epithelial ovarian cancer is initiated by the CD44v6‐positive subpopulation, and CD44v6 expression is a biomarker for the clinical outcome of advanced ovarian cancer patients. Given that a distinct subpopulation of CD44v6‐positive cancer cells plays a critical role in peritoneal metastasis, definitive treatment should target this subpopulation of CD44v6‐positive cells in epithelial ovarian cancer.
The role of CD44v6‐positive cancer cells in epithelial ovarian cancer
To assess the clinical characteristics and endocrinological background of women with vascular retained products of conception (RPOC) after miscarriage or abortion and evaluate the effect of ...estrogen–progestogen therapy (EPT) as an initial treatment on this population based on their endocrinological background.
Women with vascular RPOC after miscarriage or abortion at less than 20 weeks of pregnancy who were given EPT (conjugated estrogen and norethisterone) were retrospectively reviewed. Their clinical characteristics, hormonal parameters, ultrasonographic findings, and outcomes were evaluated.
Of 35 women with vascular RPOC, 30 (86%) presented with vaginal bleeding at a visit, and 6 (17%) required inpatient management due to heavy bleeding. Among women who presented with vaginal bleeding, serum progesterone levels were significantly lower (0.25 vs. 6.5 ng/mL, p = 0.004) than those in women who did not present with vaginal bleeding. There were no differences in serum hCG levels (10.5 vs. 3.1 mIU/mL) or serum estradiol levels (65.4 vs. 162.3 pg/mL). After withdrawal bleeding following the first course of EPT, vaginal bleeding was stopped in 27 of the 30 women (90%), and 23 (66%) of all women had a thin and linear endometrium. All women could be treated by up to two courses of EPT and did not require additional interventions. The median duration to hCG normalization after the initial EPT was 24.5 (9–88) days.
Women with vascular RPOC who have no bleeding had significantly higher levels of serum progesterone, indicating that administration of progestogen may have an effect on hemostasis. Endometrial bleeding can be prevented or stopped, and retained tissues can be conservatively expelled by oral administration of EPT, including norethisterone, in women with vascular RPOC.
We aimed to elucidate the pathogenesis of ovarian cancer through the loss of mismatch repair (MMR) proteins in women with Lynch syndrome (LS) in this report.
Two women with LS underwent surgery for ...synchronous endometrial cancer and ovarian cancer. In both cases, immunohistochemical examination showed concomitant MMR protein deficiency in endometrial cancer, ovarian cancer, and contiguous ovarian endometriosis. In Case 1, the macroscopically normal ovary included multiple endometrioses with MSH2 and MSH6 expression, and FIGO grade 1 endometrioid carcinoma and contiguous endometriosis without MSH2 and MSH6 expression. In Case 2, all endometriotic cells contiguous with carcinoma in the lumen of the ovarian cyst showed loss of the expression of MSH2 and MSH6.
Ovarian endometriosis with MMR protein deficiency may progress to endometriosis-associated ovarian cancer in women with LS. Diagnosing endometriosis in women with LS during surveillance is important.
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