Smoking Cessation Support: A Marathon, Not a Sprint; The Perspectives of Cancer Patients Who Smoke.

OBJECTIVES: Despite the unfavorable outcomes associated with continued smoking, a substantial proportion of patients with cancer continue to smoke after diagnosis. However, limited use of smoking cessation (SC) interventions has been reported. This study explored the perceptions of patients with cancer who continue to smoke/recently quit regarding SC. DATA SOURCES: Semistructured phone/Zoom/Webex interviews were conducted with 25 participants attending four Irish cancer hospitals who were current smokers or had quit at/after their cancer diagnosis. Thematic analysis was used to analyze the data. CONCLUSION: A total of four key themes emerged: (1) Diagnosis was a shock and a cue to action. (2) Brief and variable SC support: most participants did not feel stigmatized and reported receiving verbal or written information from oncology healthcare providers (HCPs) on SC supports. However, use of SC services was limited and largely ineffective. Some participants reported that SC discussions occurred earlier in their treatment with limited/no discussion later. (3) Facilitators vs barriers: the presence or absence of willpower and motivation was perceived as important. Family and HCP support helped while stress hindered SC. (4) SC support is a "marathon," not a "sprint." Patients with cancer who continue to smoke or recently quit want a sustained, tailored, nonjudgmental approach to SC incorporating pharmacological and behavioral interventions that span hospital-/community-based settings. IMPLICATIONS FOR NURSING PRACTICE: While consultants have been identified as the key HCP to initiate the SC discussion, oncology nurses can support patients with cancer who smoke/recently quit by advocating for comprehensive SC services and by using positive messaging and encouragement.

Specialist cancer hospital-based smoking cessation service provision in Ireland.

BACKGROUND: While much progress has been made in reducing tobacco use in many countries, both active and passive smoking remain challenges. The benefits of smoking cessation are universally recognized, and the hospital setting is an ideal setting where smokers can access smoking cessation services as hospital admission can be a cue to action. Consistent delivery of good quality smoking cessation care across health services is an important focus for reducing the harm of tobacco use, especially among continued smokers. AIMS: Our objective was to document the smoking cessation medication and support services provided by specialist adult cancer hospitals across Ireland, a country with a stated tobacco endgame goal. METHODS: A cross-sectional survey based on recent national clinical guidelines was used to determine smoking cessation care delivery across eight specialist adult cancer tertiary referral university hospitals and one specialist radiotherapy center. Survey responses were collected using Qualtrics, a secure online survey software tool. The data was grouped, anonymized, and analyzed in Microsoft Excel. RESULTS: All responding hospitals demonstrated either some level of smoking cessation information or a service available to patients. However, there is substantial variation in the type and level of smoking cessation information offered, making access to smoking cessation services inconsistent and inequitable. CONCLUSION: The recently launched National Clinical Guideline for smoking cessation provides the template for all hospitals to ensure health services are in a position to contribute to Ireland's tobacco endgame goal.

P53 and TLR4 expression are prognostic markers informing progression free survival of advanced stage high grade serous ovarian cancer.

OBJECTIVE: New prognostic biomarkers, and bio-signatures, are urgently needed to facilitate a precision medicine-based approach to more effectively treat patients with high-grade serous ovarian cancer (HGSC). In this study, we analysed the expression patterns of a series of candidate protein biomarkers. METHODS: The panel of markers which included MyD88, TLR4, MAD2, PR, OR, WT1, p53, p16, CD10 and Ki67 was assessed using immunohistochemistry in a tissue microarray (TMA) cohort of n = 80 patients, composed of stage 3-4 HGSCs. Each marker was analysed for their potential to predict both overall survival (OS) and progression-free survival (PFS). RESULTS: TLR4 and p53 were found to be individually predictive of poorer PFS (Log Rank, p = 0.017, p = 0.030 respectively). Cox regression analysis also identified high p53 and TLR4 expression as prognostic factors for reduced PFS (p53; HR=1.785, CI=1.036-3.074, p = 0.037 and TLR4; HR=2.175, CI=1.112-4.253, p = 0.023). Multivariate forward conditional Cox regression analysis, examining all markers, identified a combined signature composed of p53 and TLR4 as prognostic for reduced PFS (p = 0.023). CONCLUSION: Combined p53 and TLR4 marker assessment may help to aid treatment stratification for patients diagnosed with advanced-stage HGSC.

Kinase Suppressor of RAS 1 (KSR1) Maintains the Transformed Phenotype of BRAFV600E Mutant Human Melanoma Cells.

Kinase Suppressor of RAS 1 (KSR1) is a scaffolding protein for the RAS-RAF-MEK-ERK pathway, which is one of the most frequently altered pathways in human cancers. Previous results have shown that KSR1 has a critical role in mutant RAS-mediated transformation. Here, we examined the role of KSR1 in mutant BRAF transformation. We used CRISPR/Cas9 to knock out KSR1 in a BRAFV600E-transformed melanoma cell line. KSR1 loss produced a complex phenotype characterised by impaired proliferation, cell cycle defects, decreased transformation, decreased invasive migration, increased cellular senescence, and increased apoptosis. To decipher this phenotype, we used a combination of proteomic ERK substrate profiling, global protein expression profiling, and biochemical validation assays. The results suggest that KSR1 directs ERK to phosphorylate substrates that have a critical role in ensuring cell survival. The results further indicate that KSR1 loss induces the activation of p38 Mitogen-Activated Protein Kinase (MAPK) and subsequent cell cycle aberrations and senescence. In summary, KSR1 function plays a key role in oncogenic BRAF transformation.

The protein and miRNA profile of plasma extracellular vesicles (EVs) can distinguish feline mammary adenocarcinoma patients from healthy feline controls.

Feline mammary adenocarcinomas (FMA) are aggressive tumours with metastatic capability and limited treatment options. This study aims to investigate whether miRNAs associated with FMA tumours are secreted in extracellular vesicles (EVs) and whether they can potentially be used as a cancer biomarker in EVs from feline plasma. Tumours and matched tumour free margins from 10 felines with FMA were selected. Following a detailed literature search, RT-qPCR analyses of 90 miRNAs identified 8 miRNAs of interest for further investigation. Tumour tissue, margins and plasma were subsequently collected from a further 10 felines with FMA. EVs were isolated from the plasma. RT-qPCR expression analyses of the 8 miRNAs of interest were carried out in tumour tissue, margins, FMA EVs and control EVs. Additionally, proteomic analysis of both control and FMA plasma derived EVs was undertaken. RT-qPCR revealed significantly increased miR-20a and miR-15b in tumours compared to margins. A significant decrease in miR-15b and miR-20a was detected in EVs from FMAs compared to healthy feline EVs. The proteomic content of EVs distinguished FMAs from controls, with the protein targets of miR-20a and miR-15b also displaying lower levels in the EVs from patients with FMA. This study has demonstrated that miRNAs are readily detectable in both the tissue and plasma derived EVs from patients with FMA. These miRNAs and their protein targets are a detectable panel of markers in circulating plasma EVs that may inform future diagnostic tests for FMA in a non-invasive manner. Moreover, the clinical relevance of miR-20a and miR-15b warrants further investigation.

A comparative analysis of extracellular vesicles (EVs) from human and feline plasma.

Extracellular vesicles (EVs) are nanoparticles found in all biological fluids, capable of transporting biological material around the body. Extensive research into the physiological role of EVs has led to the development of the Minimal Information for Studies of Extracellular Vesicles (MISEV) framework in 2018. This framework guides the standardisation of protocols in the EV field. To date, the focus has been on EVs of human origin. As comparative medicine progresses, there has been a drive to study similarities between diseases in humans and animals. To successfully research EVs in felines, we must validate the application of the MISEV guidelines in this group. EVs were isolated from the plasma of healthy humans and felines. EV characterisation was carried out according to the MISEV guidelines. Human and feline plasma showed a similar concentration of EVs, comparable expression of known EV markers and analogous particle to protein ratios. Mass spectrometry analyses showed that the proteomic signature of EVs from humans and felines were similar. Asymmetrical flow field flow fractionation, showed two distinct subpopulations of EVs isolated from human plasma, whereas only one subpopulation was isolated from feline plasma. Metabolomic profiling showed similar profiles for humans and felines. In conclusion, isolation, and characterisation of EVs from humans and felines show that MISEV2018 guidelines may also be applied to felines. Potential comparative medicine studies of EVs may provide a model for studying naturally occurring diseases in both humans and felines.

Has the National Fall in Smoking Rates in Ireland Been Replicated in Cancer Patients? A 5-Year Report.

Smoking among cancer patients leads to poorer outcomes, yet many patients continue smoking. As part of a feasibility study of smoking cessation for cancer patients in Ireland, smoking rates were reviewed. Hospital Inpatient Enquiry (HIPE) data on the smoking status of discharges with a cancer diagnosis (overall, breast, lung, cervical and head and neck cancer) were used (2014-2018). During 2014-2017, current smoking increased for overall (10.5-11.7%) and lung cancer (24.7-27.2%), then decreased to 11.4% and 24.1%, respectively, in 2018. Current smoking increased for cervical during 2014-2018 (11-19.8%) and initially (2014-2016) for head and neck (3-12.7%) cancer, decreasing to 7.6% in 2018; breast cancer was stable at 6 ± 0.6%. These rates are lower than the Irish (23-20%) and European (29% (average)) general population. During 2014-2017, past smoking increased among overall (15.2-21%) and specific cancers, which was lower than the Irish general population (23-28%). Current smoking was highest among 50-59-year-olds (14-16%), which contrasts with the Irish general population (24-35 years at 32-28%). HIPE data are subject to potential duplicate episodes of care and under-documentation of smoking. However, trend analysis is useful, as these limitations should be stable. Rates remain high; therefore, robust documentation and smoking cessation referrals for cancer patients are important.

Verbalisation of attention regulation strategies and background music enhance extinction learning and retention.

Relapse and return of fear are common following exposure-based treatments which aim to decrease anxiety by reducing danger expectancies and negative stimulus evaluations. Using Pavlovian conditioning and extinction procedures, recent studies found that verbalising catchphrases to prompt attention to, and memory of, stimulus contingencies during extinction prevented US expectancy generalisation to safe stimuli and reduced anxiety ratings. Verbalizations did not improve negative evaluations of conditional stimuli. Given that negative evaluations predict return of fear, the current study examined whether verbalisation strategies combined with listening to liked, non-lyrical background music enhanced expectancy learning and positively changed stimulus evaluations. A differential Pavlovian conditioning procedure was used involving fear acquisition, extinction, and extinction retest phases. Participants were assigned to a verbalisation condition (N = 21), a verbalisation plus liked, non-lyrical music condition (N = 21) or a control condition (N = 21) during extinction. The verbalisation strategies, with and without music, prevented the generalisation of US expectancies to safe stimuli at retest. Verbalisation strategies plus music increased positive evaluations of conditional stimuli during extinction and retest. Further research on the role of verbalising attention regulation strategies and liked, non-lyrical background music during extinction is warranted with clinical samples.

Comparative gene expression study highlights molecular similarities between triple negative breast cancer tumours and feline mammary carcinomas.

Triple negative breast cancer (TNBC) is a rare, highly metastatic subtype of breast cancer that typically develops tumours of a high histological grade. As TNBC is negative for the oestrogen, progesterone and HER2 receptors it is also not eligible for targeted hormonal therapies. Therefore, those diagnosed with TNBC are faced with a very poor prognosis. Feline mammary carcinomas (FMCs) have been shown to share key characteristics of TNBC and are being investigated as novel animal models of this disease. A study by Granados-Soler et al., investigating prognostic markers of FMCs provided the basis of this research, and their prognostic value in TNBC was evaluated using a 'data-mining' research approach. Overall, the comparative genomic aspect of this research identified several potential prognostic markers translatable across TNBC and FMCs. These prognostic markers warrant further investigation in comparative oncology studies.

The potential role of cofilin-1 in promoting triple negative breast cancer (TNBC) metastasis via the extracellular vesicles (EVs).

Triple negative breast cancer (TNBC) is an aggressive cancer, particularly prone to metastasis and is associated with poor survival outcomes. The key to unravelling the aggressiveness of TNBC lies in decoding the mechanism by which it metastasises. Cofilin-1 is a well-studied member of the cofilin family, involved in actin depolymerisation. Studies have described the diverse roles of cofilin-1 including cell motility, apoptosis and lipid metabolism. Levels of cofilin-1 have been shown to be increased in many different types of malignant cells, with increased cofilin-1 protein levels associated with poor prognosis in patients with TNBC. Extracellular vesicles (EVs) are microvesicles typically around 100 nm in size, found in all biological fluids examined to date (Lötvall et al., 2014). Proteomic studies on extracellular vesicles (EVs) have shown that cofilin-1 is amongst the most frequently detected. Moreover, decreased levels of cofilin-1 potentially inhibit the release of EVs from cells. Additionally, Cofilin-1 is essential for the maturation of EVs and may also play a key role in the establishment of the pre-metastatic niche, thus promoting tumour cell migration. Further work into the exact mechanism by which cofilin-1 advances TNBC metastasis, may potentially prevent disease progression and improve outcomes for patients with TNBC.

"Could you give us an idea on what we are all doing here?" the Patient Voice in Cancer Research (PVCR) starting the journey of involvement in Ireland.

BACKGROUND: Involving patients and their carers in research has become more common, as funders demand evidence of involvement. The 'Patient Voice in Cancer Research' (PVCR) is an initiative led by University College Dublin (UCD) in Ireland. It encourages and enables people affected by cancer, and their families to become involved in shaping and informing the future of cancer research across the island of Ireland. Its aim is to identify the questions and needs that matter most to (i) people living with a cancer diagnosis, and (ii) those most likely to improve the relevance of cancer research. The initiative commenced in April 2016. METHODS: This paper presents a reflective case study of our journey thus far. We outline three key stages of the initiative and share what we have learnt. At the core of PVCR, is a focus on building long-term relationships. RESULTS: We have developed over time an inclusive initiative that is built on trust and respect for everyone's contributions. This work is grounded on collegiality, mixed with a good sense of humour and friendship. CONCLUSION: The development of PVCR has taken time and investment. The benefits and impact of undertaking this work have been immensely rewarding and now require significant focus as we enhance cancer research across the island of Ireland.

5-AZA-dC induces epigenetic changes associated with modified glycosylation of secreted glycoproteins and increased EMT and migration in chemo-sensitive cancer cells.

BACKGROUND: Glycosylation, one of the most fundamental post-translational modifications, is altered in cancer and is subject in part, to epigenetic regulation. As there are many epigenetic-targeted therapies currently in clinical trials for the treatment of a variety of cancers, it is important to understand the impact epi-therapeutics have on glycosylation. RESULTS: Ovarian and triple negative breast cancer cells were treated with the DNA methyltransferase inhibitor, 5-AZA-2-deoxycytidine (5-AZA-dC). Branching and sialylation were increased on secreted N-glycans from chemo-sensitive/non-metastatic cell lines following treatment with 5-AZA-dC. These changes correlated with increased mRNA expression levels in MGAT5 and ST3GAL4 transcripts in ovarian cancer cell lines. Using siRNA transient knock down of GATA2 and GATA3 transcription factors, we show that these regulate the glycosyltransferases ST3GAL4 and MGAT5, respectively. Moreover, 5-AZA-dC-treated cells displayed an increase in migration, with a greater effect seen in chemo-sensitive cell lines. Western blots showed an increase in apoptotic and senescence (p21) markers in all 5-AZA-dC-treated cells. The alterations seen in N-glycans from secreted glycoproteins in 5-AZA-dC-treated breast and ovarian cancer cells were similar to the N-glycans previously known to potentiate tumour cell survival. CONCLUSIONS: While the FDA has approved epi-therapeutics for some cancer treatments, their global effect is still not fully understood. This study gives insight into the effects that epigenetic alterations have on cancer cell glycosylation, and how this potentially impacts on the overall fate of those cells.

The role of von Willebrand factor in breast cancer metastasis.

Breast cancer is the most common female cancer globally, with approximately 12% of patients eventually developing metastatic disease. Critically, limited effective treatment options exist for metastatic breast cancer. Recently, von Willebrand factor (VWF), a haemostatic plasma glycoprotein, has been shown to play an important role in tumour progression and metastasis. In breast cancer, a significant rise in the plasma levels of VWF has been reported in patients with malignant disease compared to benign conditions and healthy controls, with an even greater increase seen in patients with disseminated disease. Direct interactions between VWF, tumour cells, platelets and endothelial cells may promote haematogenous dissemination and thus the formation of metastatic foci. Intriguingly, patients with metastatic disease have unusually large VWF multimers. This observation has been proposed to be a result of a dysfunctional or deficiency of VWF-cleaving protease activity, ADAMTS-13 activity, which may then regulate the platelet-tumour adhesive interactions in the metastatic process. In this review, we provide an overview of VWF in orchestrating the pathological process of breast cancer dissemination, and provide supporting evidence of the role of VWF in mediating metastatic breast cancer.

Research Strategies for Low-Survival Cancers.

While substantial progress has been made to improve the diagnosis, prognosis, and survivorship of patients with cancer, certain cancer types, along with metastatic and refractory disease, remain clinical challenges. To improve patient outcomes, ultimately, the cancer research community must meet and overcome these challenges, leading to improved approaches to treat the most difficult cancers. Here, we discuss research progress aimed at gaining a better understanding of the molecular and cellular changes in tumor cells and the surrounding stroma, presented at the 56th Irish Association for Cancer Research (IACR) Annual Conference. With a focus on poor prognosis cancers, such as esophageal and chemo-resistant colorectal cancers, we highlight how detailed molecular knowledge of tumor and stromal biology can provide windows of opportunity for biomarker discovery and therapeutic targets. Even with previously characterized targets, such as phosphoinositide 3-kinase (PI3K), one of the most altered proteins in all human cancers, new insights into how this protein may be more effectively inhibited through novel combination therapies is presented.

N-Linked glycosylation profiles of therapeutic induced senescent (TIS) triple negative breast cancer cells (TNBC) and their extracellular vesicle (EV) progeny.

Triple negative breast cancer (TNBC) has poor clinical outcomes and limited treatment options. Chemotherapy, while killing some cancer cells, can result in therapeutic-induced-senescent (TIS) cells. Senescent cells release significantly more extracellular vesicles (EVs) than non-senescent cells. Recently, N- and O-linked glycosylation alterations have been associated with senescence. We aimed to profile the N-linked glycans of whole cells, membrane, cytoplasm and EVs harvested from TIS TNBC cells and to compare these to results from non-senescent cells. TIS was induced in the Cal51 TNBC cells using the chemotherapeutic agent paclitaxel (PTX). Ultra-performance liquid chromatography (UPLC) analysis of exoglycosidase digested N-linked glycans was carried out on TIS compared to non-treated control cells. LC-Mass spectrometry (MS) analysis of the N-linked glycans and lectin blotting of samples was carried out to confirm the UPLC results. Significant differences were found in the N-glycan profile of the Cal51 membrane, cytoplasm and EV progeny of TIS compared to non-senescent cells. Protein mass spectrometry showed that the TIS cells contain different glycan modifying enzymes. The lectin, calnexin demonstrated a lower kDa size (∼58 kDa) in TIS compared to control cells (∼90 kDa) while Galectin 3 demonstrated potential proteolytic cleavage with 32 kDa and ∼22 kDa bands evident in TIS compared to non-senescent control cells with a major 32 kDa band only. TIS CAL51 cells also demonstrated a reduced adhesion to collagen I compared to control non-senescent cells. This study has shown that therapeutic-induced-senescent TNBC cells and their EV progeny, display differential N-glycan moieties compared to non-senescent Cal51 cells and their resultant EV progeny. For the future, N-glycan moieties on cancer senescent cells and their EV progeny hold potential for (i) the monitoring of treatment response as a liquid biopsy, and (ii) cancer senescent cell targeting with lectin therapies.

Circulating Melanoma-Derived Extracellular Vesicles: Impact on Melanoma Diagnosis, Progression Monitoring, and Treatment Response.

Malignant melanoma, one of the most aggressive human malignancies, is responsible for 80% of skin cancer deaths. Whilst early detection of disease progression or metastasis can improve patient survival, this remains a challenge due to the lack of reliable biomarkers. Importantly, these clinical challenges are not unique to humans, as melanoma affects many other species, including companion animals, such as the dog and horse. Extracellular vesicles (EVs) are tiny nanoparticles involved in cell-to-cell communication. Several protein and genomic EV markers have been described in the literature, as well as a wide variety of methods for isolating EVs from body fluids. As such, they may be valuable biomarkers in cancer and may address some clinical challenges in the management melanoma. This review aimed to explore the translational applications of EVs as biomarkers in melanoma, as well as their role in the clinical setting in humans and animals. A summary of melanoma-specific protein and genomic EV markers is presented, followed by a discussion of the role EVs in monitoring disease progression and treatment response. Finally, herein, we reviewed the advantages and disadvantages of methods utilised to isolate EVs from bodily fluids in melanoma patients (human and animals) and describe some of the challenges that will need to be addressed before EVs can be introduced in the clinical setting.

The role of the MAD2-TLR4-MyD88 axis in paclitaxel resistance in ovarian cancer.

Despite the use of front-line anticancer drugs such as paclitaxel for ovarian cancer treatment, mortality rates have remained almost unchanged for the past three decades and the majority of patients will develop recurrent chemoresistant disease which remains largely untreatable. Overcoming chemoresistance or preventing its onset in the first instance remains one of the major challenges for ovarian cancer research. In this study, we demonstrate a key link between senescence and inflammation and how this complex network involving the biomarkers MAD2, TLR4 and MyD88 drives paclitaxel resistance in ovarian cancer. This was investigated using siRNA knockdown of MAD2, TLR4 and MyD88 in two ovarian cancer cell lines, A2780 and SKOV-3 cells and overexpression of MyD88 in A2780 cells. Interestingly, siRNA knockdown of MAD2 led to a significant increase in TLR4 gene expression, this was coupled with the development of a highly paclitaxel-resistant cell phenotype. Additionally, siRNA knockdown of MAD2 or TLR4 in the serous ovarian cell model OVCAR-3 resulted in a significant increase in TLR4 or MAD2 expression respectively. Microarray analysis of SKOV-3 cells following knockdown of TLR4 or MAD2 highlighted a number of significantly altered biological processes including EMT, complement, coagulation, proliferation and survival, ECM remodelling, olfactory receptor signalling, ErbB signalling, DNA packaging, Insulin-like growth factor signalling, ion transport and alteration of components of the cytoskeleton. Cross comparison of the microarray data sets identified 7 overlapping genes including MMP13, ACTBL2, AMTN, PLXDC2, LYZL1, CCBE1 and CKS2. These results demonstrate an important link between these biomarkers, which to our knowledge has never before been shown in ovarian cancer. In the future, we hope that triaging patients into alterative treatment groups based on the expression of these three biomarkers or therapeutic targeting of the mechanisms they are involved in will lead to improvements in patient outcome and prevent the development of chemoresistance.

HDAC6 Degradation Inhibits the Growth of High-Grade Serous Ovarian Cancer Cells.

Histone deacetylase 6 (HDAC6) is a unique histone deacetylating enzyme that resides in the cell cytoplasm and is linked to the modulation of several key cancer related responses, including cell proliferation and migration. The promising anti-cancer response of the first-generation HDAC6 catalytic inhibitors continues to be assessed in clinical trials, although its role in high grade serous ovarian cancer is unclear. This study investigated HDAC6 tumor expression by immunohistochemistry in high-grade serous ovarian cancer (HGSOC) tissue samples and a meta-analysis of HDAC6 gene expression in ovarian cancer from publicly available data. The pharmacological activity of HDAC6 inhibition was assessed in a patient-derived model of HGSOC. HDAC6 was found to be highly expressed in HGSOC tissue samples and in the patient-derived HGSOC cell lines where higher HDAC6 protein and gene expression was associated with a decreased risk of death (hazard ratio (HR) 0.38, (95% confidence interval (CI), 0.16-0.88; p = 0.02); HR = 0.88 (95% CI, 0.78-0.99; p = 0.04)). Similarly, the multivariate analysis of HDAC6 protein expression, adjusting for stage, grade, and cytoreduction/cytoreductive surgery was associated with a decreased risk of death (HR = 0.19 (95% CI, 0.06-0.55); p = 0.002). Knock-down of HDAC6 gene expression with siRNA and protein expression with a HDAC6 targeting protein degrader decreased HGSOC cell proliferation, migration, and viability. Conversely, the selective inhibition of HDAC6 with the catalytic domain inhibitor, Ricolinostat (ACY-1215), inhibited HDAC6 deacetylation of α-tubulin, resulting in a sustained accumulation of acetylated α-tubulin up to 24 h in HGSOC cells, did not produce a robust inhibition of HDAC6 protein function. Inhibition of HGSOC cell proliferation by ACY-1215 was only achieved with significantly higher and non-selective doses of ACY-1215. In summary, we demonstrated, for the first time, that HDAC6 over-expression in HGSOC and all ovarian cancers is a favorable prognostic marker. We provide evidence to suggest that inhibition of HDAC6 catalytic activity with first generation HDAC6 inhibitors has limited efficacy as a monotherapy in HGSOC.