Human epididymis protein 4 (HE4) is an important clinical biomarker used for the detection of epithelial ovarian cancer (EOC). While much is known about the predictive power of HE4 clinically, less has been reported regarding its molecular role in the progression of EOC. A deeper understanding of HE4’s mechanistic functions may help contribute to the development of novel targeted therapies. Thus far, it has been difficult to recommend HE4 as a therapeutic target owing to the fact that its role in the progression of EOC has not been extensively evaluated. This review summarizes what is collectively known about HE4 signaling and how it functions to promote tumorigenesis, chemoresistance, and metastasis in EOC, with the goal of providing valuable insights that will have the potential to aide in the development of new HE4-targeted therapies.

Chemotherapy resistance presents a difficult challenge in treating epithelial ovarian cancer patients, particularly when tumors exhibit resistance to multiple chemotherapeutic agents. A few studies have shown that elevated serum levels of the ovarian cancer biomarker HE4 correlate with tumor chemoresistance, response to treatment, and survival. Here, we sought to confirm our previous results that HE4 contributes to collateral resistance to cisplatin and paclitaxel in vitro and uncover factors that may contribute to HE4-mediated chemoresistance. MTS assays and western blots for cleaved PARP were used to assess resistance of HE4-overexpressing SKOV3 and OVCAR8 clones to cisplatin and paclitaxel. CRISPR/Cas technology was used to knockdown HE4 in HE4-overexpressing SKOV3 cells. A microarray was conducted to determine differential gene expression between SKOV3 null vector-transfected and HE4-overexpressing clones upon cisplatin exposure, and results were validated by quantitative RT-PCR. Regulation of mitogen activated protein kinases (MAPKs) and tubulins were assessed by western blot. HE4-overexpressing SKOV3 and OVCAR8 clones displayed increased resistance to cisplatin and paclitaxel. Knockdown of HE4 in HE4-overexpressing SKOV3 cells partially reversed chemoresistance. Microarray analysis revealed that HE4 overexpression resulted in suppression of cisplatin-mediated upregulation of EGR1, a MAPK-regulated gene involved in promoting apoptosis. Upregulation of p38, a MAPK activated in response to cisplatin, was suppressed in HE4-overexpressing clones. No differences in extracellular signal-regulated kinase (ERK) activation were noted in HE4-overexpressing clones treated with 25 μM cisplatin, but ERK activation was partially suppressed in HE4-overexpressing clones treated with 80 μM cisplatin. Furthermore, treatment of cells with recombinant HE4 dramatically affected ERK activation in SKOV3 and OVCAR8 wild type cells. Recombinant HE4 also upregulated α-tubulin and β-tubulin levels in SKOV3 and OVCAR8 cells, and microtubule associated protein tau (MAPT) gene expression was increased in SKOV3 HE4-overexpressing clones. Overexpression of HE4 promotes collateral resistance to cisplatin and paclitaxel, and downregulation of HE4 partially reverses this chemoresistance. Multiple factors could be involved in HE4-mediated chemoresistance, including deregulation of MAPK signaling, as well as alterations in tubulin levels or stability.

Purpose: Plasma-based liquid biopsy tests can detect tumor-specific genetic alterations and offer many advantages that complement tissue-based comprehensive genomic profiling. However, age-related clonal hematopoiesis (CH) mutations can confound liquid biopsy results and potentially lead to incorrect therapy choice. Experimental Design: We assessed the landscape of 16,812 liquid profiles across 49 cancer types using the Caris Assure assay, a whole-exome and whole-transcriptome next-generation sequencing workflow that independently sequences both plasma-derived cell-free total nucleic acids and the white blood cell DNA and RNA from the buffy coat. The variant source was identified algorithmically by comparing plasma and buffy coat variant frequency and read quality metrics. Results: Of 16,812 patients, 42.3% presented at least one CH variant among reportable clinical genes. We found 39% of BRCA2 variants to be of CH origin, as well as 37.9% of CHEK2, 27.4% of BRCA1, 20.1% of ATM, 7.3% of NRAS, 5.8% of BRAF, 2.1% of EGFR, 2.1% of KRAS, and 18.5% of TP53. For patients aged 65 to 69 years, the median proportion of CH variant classification was 20%, whereas it was 33% for patients aged 70 to 74 years, 33% for ages 75 to 79 years, and 50% for ages 80+ years. We found high rates of CH detected in what would be otherwise druggable targets in many cancer types typically treated with PARP inhibitors, including breast, female genital tract, ovarian, pancreatic, prostate, and endometrial cancers. Conclusions: This large study highlights the need for thorough CH classification during liquid biopsy to appropriately recommend therapies, especially PARP inhibitors. See related commentary by Bernard and Micol, p. 2545

Epithelial ovarian cancer (EOC) is a highly lethal gynecologic malignancy arising from the fallopian tubes that has a high rate of chemoresistant recurrence and low five-year survival rate. The ovarian cancer biomarker HE4 is known to promote proliferation, metastasis, chemoresistance, and suppression of cytotoxic lymphocytes. In this study, we sought to examine the effects of HE4 on signaling within diverse cell types that compose the tumor microenvironment. HE4 was found to activate STAT3 signaling and promote upregulation of the pro-angiogenic STAT3 target genes IL8 and HIF1A in immune cells, ovarian cancer cells, and endothelial cells. Moreover, HE4 promoted increases in tube formation in an in vitro model of angiogenesis, which was also dependent upon STAT3 signaling. Clinically, HE4 and IL8 levels positively correlated in ovarian cancer patient tissue. Furthermore, HE4 serum levels correlated with microvascular density in EOC tissue and inversely correlated with cytotoxic T cell infiltration, suggesting that HE4 may cause deregulated blood vessel formation and suppress proper T cell trafficking in tumors. Collectively, this study shows for the first time that HE4 has the ability to affect signaling events and gene expression in multiple cell types of the tumor microenvironment, which could contribute to angiogenesis and altered immunogenic responses in ovarian cancer.

Oncotarget | https://doi.org/10.18632/oncotarget.26915 Nicole E. James, Lindsey Beffa, Matthew T. Oliver, Ashley D. Borgstadt, Jenna B. Emerson, Clinton O. Chichester, Naohiro Yano, Richard N. Freiman, Paul A....