Variations in potassium channel genes are associated with breast pain in women prior to breast cancer surgery

C-type inactivation and proton modulation mechanisms of the TASK3 channel

The TWIK-related acid-sensitive K+ channel 3 (TASK3) belongs to the two-pore domain (K2P) potassium channel family, which regulates cell excitability by mediating a constitutive "leak" potassium efflux in the nervous system. Extracellular acidification inhibits TASK3 channel, but the molecular mechanism by which channel inactivation is coupled to pH decrease remains unclear. Here, we report the cryo-electron microscopy structures of human TASK3 at neutral and acidic pH. Structural comparison revealed selectivity filter (SF) rearrangements upon acidification, characteristic of C-type inactivation, but with a unique structural basis. The extracellular mouth of the SF was prominently dilated and simultaneously blocked by a hydrophobic gate. His98 protonation shifted the conformational equilibrium between the conductive and C-type inactivated SF toward the latter by engaging a cation-π interaction with Trp78, consistent with molecular dynamics simulations and electrophysiological experiments. Our work illustrated how TASK3 is gated in response to extracellular pH change and implies how physiological stimuli might directly modulate the C-type gating of K2P channels.

Parthenolide as a potential analgesic in the treatment of paclitaxel-induced neuropathic pain: the rat modeling

In this study, we determined the therapeutic effect of parthenolide (PTL), the active component of Tanacetum parthenium, on neuropathic pain caused by paclitaxel (PTX), a chemotherapeutic drug frequently used in cancer treatment, at the gene and protein levels. To this end, 6 groups were formed: control, PTX, sham, 1 mg/PTL, 2 mg/kg PTL, and 4 mg/kg PTL. Pain formation was tested by Randall-Selitto analgesiometry and locomotor activity behavioral analysis. Then, PTL treatment was performed for 14 days. After the last dose of PTL was taken, Hcn2, Trpa1, Scn9a, and Kcns1 gene expressions were measured in rat brain (cerebral cortex/CTX) tissues. In addition, changes in the levels of SCN9A and KCNS1 proteins were determined by immunohistochemical analysis. Histopathological hematoxylin-eosin staining was also performed to investigate the effect of PTL in treating tissue damage on neuropathic pain caused by PTX treatment. When the obtained data were analyzed, pain threshold and locomotor activity decreased in PTX and sham groups and increased with PTL treatment. In addition, it was observed that the expression of the Hcn2, Trpa1, and Scn9a genes decreased while the Kcns1 gene expression increased. When protein levels were examined, it was determined that SCN9A protein expression decreased and the KCNS1 protein level increased. It was determined that PTL treatment also improved PTX-induced tissue damage. The results of this study demonstrate that non-opioid PTL is an effective therapeutic agent in the treatment of chemotherapy-induced neuropathic pain, especially when used at a dose of 4 mg/kg acting on sodium and potassium channels.

Epigenomic Analysis Reveals the KCNK9 Potassium Channel as a Potential Therapeutic Target for Adenomyosis

Adenomyosis is linked to dysmenorrhea and infertility. The pathogenesis of adenomyosis remains unclear, and little is known of the genetic and epigenetic changes in the eutopic endometrium in adenomyosis, which may predispose patients to the invasion and migration of endometrial tissues into the myometrium. Transcriptome studies have identified genes related to various cell behaviors but no targets for therapeutic intervention. The epigenetics of the eutopic endometrium in adenomyosis have rarely been investigated. Endometrial tissue was obtained from premenopausal women with (n = 32) or without adenomyosis (n = 17) who underwent hysterectomy aged 34–57 years at a tertiary hospital. The methylome and transcriptome were assessed by using a Methylation 450 K BeadChip array and Affymetrix expression microarray. Protein expression was examined by immunohistochemistry. Differential methylation analysis revealed 53 lowly methylated genes and 176 highly methylated genes with consistent gene expression in adenomyosis, including three genes encoding potassium ion channels. High expression of KCNK9 in the eutopic and ectopic endometria in patients with adenomyosis but not in normal controls was observed. Hormone-free, antibody-based KCNK9 targeting is a potential therapeutic strategy for adenomyosis-related dysmenorrhea, menorrhagia, and infertility.

Co-expression of cancer-testis antigens of MAGE-A6 and MAGE-A11 is associated with tumor aggressiveness in patients with bladder cancer

Melanoma antigen gene (MAGE)-A6 and MAGE-A11 are two of the most cancer-testis antigens overexpressed in various types of cancers. However, the clinical and prognosis value of MAGE-A6 and MAGE-A11 co-expression in the pathophysiology of the bladder is unknown. Three studies were selected from GEO databases in order to introduce the common genes that are involved in bladder cancer. Then immunohistochemical analysis for staining pattern and clinicopathological significance of suggested markers, MAGE-A6 and MAGE-A11, were performed in 199 and 213 paraffin-embedded bladder cancer with long adjacent normal tissues, respectively. A significant and positive correlation was found between both nuclear and cytoplasmic expressions of MAGE-A6 as well as expression of cytoplasmic MAGE-A11 with histological grade, PT stage, lamina propria invasion, and LP/ muscularis (L/M) involvement (all of the p-values in terms of H-score were < 0.0001). Additionally, significant differences were found between both nuclear and cytoplasmic MAGE-A6/MAGE-A11 phenotypes with tumor size (P = 0.007, P = 0.043, respectively), different histological grades, PT stage, LP involvement, and L/M involvement (all of the p-values for both phenotypes were < 0.0001). The current study added the value of these novel markers to the bladder cancer clinical settlement that might be considered as an admirable target for immunotherapy.

Chronic Breast Pain Prior to Breast Cancer Surgery Is Associated with Worse Acute Postoperative Pain Outcomes

Acute postoperative pain is associated with adverse short and long-term outcomes among women undergoing surgery for breast cancer. Previous studies identified preexisting pain as a predictor of postoperative pain, but rarely accounted for pain location or chronicity. This study leveraged a multinational pain registry, PAIN OUT, to: (1) characterize patient subgroups based on preexisting chronic breast pain status and (2) determine the association of preexisting chronic pain with acute postoperative pain-related patient-reported outcomes and opioid consumption following breast cancer surgery. The primary outcome was a composite score comprising the mean of pain intensity and pain interference items from the International Pain Outcomes Questionnaire. The secondary outcome was opioid consumption in the recovery room and ward. Among 1889 patients, we characterized three subgroups: no preexisting chronic pain (n = 1600); chronic preexisting pain elsewhere (n = 128) and; chronic preexisting pain in the breast with/without pain elsewhere (n = 161). Controlling for covariates, women with preexisting chronic breast pain experienced more severe acute postoperative pain and pain interference (β = 1.0, 95% CI = 0.7-1.3, p < 0.001), and required higher doses of opioids postoperatively (β = 2.7, 95% CI = 0.6–4.8, p = 0.013). Preexisting chronic breast pain may be an important risk factor for poor pain-related postoperative outcomes. Targeted intervention of this subgroup may improve recovery.

A "Target Class" Screen to Identify Activators of Two-Pore Domain Potassium (K2P) Channels

Two-pore domain potassium (K2P) channels carry background (or leak) potassium current and play a key role in regulating resting membrane potential and cellular excitability. Accumulating evidence points to a role for K2Ps in human pathophysiologies, most notably in pain and migraine, making them attractive targets for therapeutic intervention. However, there remains a lack of selective pharmacological tools. The aim of this work was to apply a “target class” approach to investigate the K2P superfamily and identify novel activators across all the described subclasses of K2P channels. Target class drug discovery allows for the leveraging of accumulated knowledge and maximizing synergies across a family of targets and serves as an additional approach to standard target-based screening. A common assay platform using baculovirus (BacMam) to transiently express K2P channels in mammalian cells and a thallium flux assay to determine channel activity was developed, allowing the simultaneous screening of multiple targets. Importantly, this system, by allowing precise titration of channel function, allows optimization to facilitate the identification of activators. A representative set of channels (THIK-1, TWIK-1, TREK-2, TASK-3, and TASK-2) were screened against a library of Food and Drug Administration (FDA)-approved compounds and the LifeArc Index Set. Activators were then analyzed in concentration–response format across all channels to assess selectivity. Using the target class approach to investigate the K2P channels has enabled us to determine which of the K2Ps are amenable to small-molecule activation, de-risk multiple channels from a technical point of view, and identify a diverse range of previously undescribed pharmacology.

Selective activation of TWIK-related acid-sensitive K+ 3 subunit-containing channels is analgesic in rodent models

The paucity of selective agonists for TWIK-related acid-sensitive K⁺ 3 (TASK-3) channel, a member of two-pore domain K⁺ (K2P) channels, has contributed to our limited understanding of its biological functions. By targeting a druggable transmembrane cavity using a structure-based drug design approach, we discovered a biguanide compound, CHET3, as a highly selective allosteric activator for TASK-3-containing K2P channels, including TASK-3 homomers and TASK-3/TASK-1 heteromers. CHET3 displayed potent analgesic effects in vivo in a variety of acute and chronic pain models in rodents that could be abolished pharmacologically or by genetic ablation of TASK-3. We further found that TASK-3-containing channels anatomically define a unique population of small-sized, transient receptor potential cation channel subfamily M member 8 (TRPM8)-, transient receptor potential cation channel subfamily V member 1 (TRPV1)-, or tyrosine hydroxylase (TH)-positive nociceptive sensory neurons and functionally regulate their membrane excitability, supporting CHET3 analgesic effects in thermal hyperalgesia and mechanical allodynia under chronic pain. Overall, our proof-of-concept study reveals TASK-3-containing K2P channels as a druggable target for treating pain.

Machine-learned analysis of the association of next-generation sequencing-based genotypes with persistent pain after breast cancer surgery

Cancer and its surgical treatment are among the most important triggering events for persistent pain, but additional factors need to be present for the clinical manifestation, such as variants in pain-relevant genes. In a cohort of 140 women undergoing breast cancer surgery, assigned based on a 3-year follow-up to either a persistent or nonpersistent pain phenotype, next-generation sequencing was performed for 77 genes selected for known functional involvement in persistent pain. Applying machine-learning and item categorization techniques, 21 variants in 13 different genes were found to be relevant to the assignment of a patient to either the persistent pain or the nonpersistent pain phenotype group. In descending order of importance for correct group assignment, the relevant genes comprised DRD1, FAAH, GCH1, GPR132, OPRM1, DRD3, RELN, GABRA5, NF1, COMT, TRPA1, ABHD6, and DRD4, of which one in the DRD4 gene was a novel discovery. Particularly relevant variants were found in the DRD1 and GPR132 genes, or in a cis-eCTL position of the OPRM1 gene. Supervised machine-learning-based classifiers, trained with 2/3 of the data, identified the correct pain phenotype group in the remaining 1/3 of the patients at accuracies and areas under the receiver operator characteristic curves of 65% to 72%. When using conservative classical statistical approaches, none of the variants passed α-corrected testing. The present data analysis approach, using machine learning and training artificial intelligences, provided biologically plausible results and outperformed classical approaches to genotype-phenotype association.

Mice lacking Kcns1 in peripheral neurons show increased basal and neuropathic pain sensitivity

Voltage-gated potassium (Kv) channels are increasingly recognised as key regulators of nociceptive excitability. Kcns1 is one of the first potassium channels to be associated with neuronal hyperexcitability and mechanical sensitivity in the rat, as well as pain intensity and risk of developing chronic pain in humans. Here, we show that in mice, Kcns1 is predominantly expressed in the cell body and axons of myelinated sensory neurons positive for neurofilament-200, including Aδ-fiber nociceptors and low-threshold Aβ mechanoreceptors. In the spinal cord, Kcns1 was detected in laminae III to V of the dorsal horn where most sensory A fibers terminate, as well as large motoneurons of the ventral horn. To investigate Kcns1 function specifically in the periphery, we generated transgenic mice in which the gene is deleted in all sensory neurons but retained in the central nervous system. Kcns1 ablation resulted in a modest increase in basal mechanical pain, with no change in thermal pain processing. After neuropathic injury, Kcns1 KO mice exhibited exaggerated mechanical pain responses and hypersensitivity to both noxious and innocuous cold, consistent with increased A-fiber activity. Interestingly, Kcns1 deletion also improved locomotor performance in the rotarod test, indicative of augmented proprioceptive signalling. Our results suggest that restoring Kcns1 function in the periphery may be of some use in ameliorating mechanical and cold pain in chronic states.

Two-pore domain potassium channels: emerging targets for novel analgesic drugs: IUPHAR Review 26

Chronic pain is a debilitating and increasingly common medical problem with few effective treatments. In addition to the direct and indirect economic burden of pain syndromes, the concomitant increase in prescriptions for narcotics has contributed to a sharp rise in deaths associated with drug misuse - the 'opioid crisis'. Together, these issues highlight the unmet clinical and social need for a new generation of safe, efficacious analgesics. The detection and transmission of pain stimuli is largely mediated by somatosensory afferent fibres of the dorsal root ganglia. These nociceptive cells express an array of membrane proteins that have received significant attention as attractive targets for new pain medications. Among these, a growing body of evidence supports a role for the two-pore domain potassium (K2P) family of K⁺ channels. Here, we provide a concise review of the K2P channels, their role in pain biology and their potential as targets for novel analgesic agents.

Menopausal-Related Symptoms in Women One Year After Breast Cancer Surgery

CONTEXT

Approximately 60% to 100% of women with breast cancer experience at least one menopausal-related symptom. Little is known about associations between menopausal status and symptoms in women 12 months after breast cancer surgery.

OBJECTIVES

The purpose of this study was to evaluate for differences in occurrence, severity, and distress of symptoms between pre- and postmenopausal women 12 months after breast cancer surgery.

METHODS

Women with breast cancer (n = 327) completed the Menopausal Symptoms Scale, which evaluated the occurrence, severity, and distress of 46 common menopausal-related symptoms. Regression analyses were used to evaluate between-group differences in the seven symptoms that occurred in 30% and more of the sample (i.e., hot flashes, night sweats, depression, daytime sweats, joint pain or stiffness, wake during the night, and numbness or tingling).

RESULTS

Of the 327 patients with breast cancer, who completed the 12-month assessment, 35.2% were premenopausal and 64.8% were postmenopausal before surgery. In the conditional models, when significant interactions were found, the differences in symptom occurrence rates between pre- and postmenopausal patients depended on their age.

CONCLUSION

Regardless of menopausal status, women reported relatively high occurrence rates for several menopausal symptoms. Associations between symptom occurrence rates and menopausal status depended on the patient's age. During the development of a survivorship care plan, clinicians need to assess symptom burden within the context of a woman's menopausal status and salient demographic and clinical characteristics. This approach will assist with the prescription of more effective interventions.

Genetic studies of human neuropathic pain conditions: a review

Numerous studies have shown associations between genetic variants and neuropathic pain disorders. Rare monogenic disorders are caused by mutations of substantial effect size in a single gene, whereas common disorders are likely to have a contribution from multiple genetic variants of mild effect size, representing different biological pathways. In this review, we survey the reported genetic contributors to neuropathic pain and submit them for validation in a 150,000-participant sample of the U.K. Biobank cohort. Successfully replicated association with a neuropathic pain construct for 2 variants in IL10 underscores the importance of neuroimmune interactions, whereas genome-wide significant association with low back pain (P = 1.3e-8) and false discovery rate 5% significant associations with hip, knee, and neck pain for variant rs7734804 upstream of the MAT2B gene provide evidence of shared contributing mechanisms to overlapping pain conditions at the molecular genetic level.

Cytokine Gene Polymorphisms Associated With Various Domains of Quality of Life in Women With Breast Cancer

CONTEXT

Little is known about the phenotypic and molecular characteristics associated with various domains of quality of life (QOL) in women after breast cancer surgery.

OBJECTIVES

In a sample of women with breast cancer (n = 398), purposes were as follows: to identify latent classes with distinct trajectories of QOL from before surgery through six months after surgery and to evaluate for differences in demographic and clinical characteristics, as well as for polymorphisms in cytokine genes, between these latent classes.

METHODS

Latent class analyses were done to identify subgroups of patients with distinct QOL outcomes. Candidate gene analyses were done to identify cytokine gene polymorphisms associated with various domains of QOL (i.e., physical, psychological, spiritual, social).

RESULTS

One latent class was identified for the psychological and spiritual domains. Two latent classes were identified for the social domain and overall QOL scores. Three latent classes were identified for the physical domain. For the physical and social domains, as well as for the overall QOL scores, distinct phenotypic characteristics (i.e., younger age, poorer functional status, higher body mass index, and receipt of adjuvant chemotherapy) and a number of cytokine gene polymorphisms (CXCL8, NFKB2, TNFSF, IL1B, IL13, and NFKB1) were associated with membership in the lower QOL classes.

CONCLUSIONS

Findings suggest that women experience distinctly different physical well-being, social well-being, and total QOL outcomes during and after breast cancer surgery. The genetic associations identified suggest that cytokine dysregulation influences QOL outcomes. However, specific QOL domains may be impacted by different cytokines.

The Genetics of Pain: Implications for Therapeutics

Pain is an increasing clinical challenge affecting about half the population, with a substantial number of people suffering daily intense pain. Such suffering can be linked to the dramatic rise in opioid use and associated deaths in the United States. There is a pressing need for new analgesics with limited side effects. Here, we summarize what we know about the genetics of pain and implications for drug development. We make the case that chronic pain is not one but a set of disease states, with peripheral drive a key element in most. We argue that understanding redundancy and plasticity, hallmarks of the nervous system, is critical in developing analgesic drug strategies. We describe the exploitation of monogenic pain syndromes and genetic association studies to define analgesic targets, as well as issues associated with animal models of pain. We appraise present-day screening technologies and describe recent approaches to pain treatment that hold promise.

Differences in symptom clusters before and twelve months after breast cancer surgery

PURPOSE

Given the inter-relatedness among symptoms, research efforts are focused on an evaluation of symptom clusters. The purposes of this study were to evaluate for differences in the number and types of menopausal-related symptom clusters assessed prior to and at 12-months after surgery using ratings of occurrence and severity and to evaluate for changes in these symptom clusters over time.

METHODS

Prior to and at 12 months after surgery, 392 women with breast cancer completed the Menopausal Symptoms Scale. Exploratory factor analyses were used to identify the symptom clusters.

RESULTS

Of the 392 women evaluated, the mean number of symptoms (out of 46) was 13.2 (±8.5) at enrollment and 10.9 (±8.2) at 12 months after surgery. Using occurrence and severity, three symptom clusters were identified prior to surgery. Five symptom clusters were identified at 12 months following surgery. Two symptom clusters (i.e., pain/discomfort and hormonal) were relatively stable across both dimensions and time points. Two symptom clusters were relatively stable across both dimensions either prior to surgery (i.e., sleep/psychological/cognitive) or at 12 months after surgery (i.e., sleep). The other four clusters (i.e., irritability, psychological/cognitive, cognitive, psychological) were identified at one time point using a single dimension.

CONCLUSIONS

While some menopausal-related symptom clusters were consistent across time and dimensions, the majority of symptoms clustered together differently depending on whether they were evaluated prior to or at 12 months after breast cancer surgery. An increased understanding of how symptom clusters change over time may assist clinicians to focus their symptom assessments and management strategies.

Potassium Channel Candidate Genes Predict the Development of Secondary Lymphedema Following Breast Cancer Surgery

BACKGROUND

Potassium (K) channels play an important role in lymph pump activity, lymph formation, lymph transport, and the functions of lymph nodes. No studies have examined the relationship between K channel candidate genes and the development of secondary lymphedema (LE).

OBJECTIVE

The study purpose was to evaluate for differences in genotypic characteristics in women who did (n = 155) or did not (n = 387) develop upper extremity LE following breast cancer treatment based on an analysis of single-nucleotide polymorphisms (SNPs) and haplotypes in 10 K channel genes.

METHODS

Upper extremity LE was diagnosed using bioimpedance resistance ratios. Logistic regression analyses were used to identify those SNPs and haplotypes that were associated with LE while controlling for relevant demographic, clinical, and genomic characteristics.

RESULTS

Patients with LE had a higher body mass index, had a higher number of lymph nodes removed, had more advanced disease, received adjuvant chemotherapy, received radiation therapy, and were less likely to have undergone a sentinel lymph node biopsy. One SNP in a voltage-gated K channel gene (KCNA1 rs4766311), four in two inward-rectifying K channel genes (KCNJ3 rs1037091 and KCNJ6 rs2211845, rs991985, rs2836019), and one in a two-pore K channel gene (KCNK3 rs1662988) were associated with LE.

DISCUSSION

These preliminary findings suggest that K channel genes play a role in the development of secondary LE.

Polymorphisms in Cytokine Genes Are Associated With Higher Levels of Fatigue and Lower Levels of Energy in Women After Breast Cancer Surgery

CONTEXT

Little is known about the phenotypic and molecular characteristics associated with changes over time in fatigue and lack of energy in patients with breast cancer.

OBJECTIVES

The aim of this study was to identify subgroups (i.e., latent classes) of women with distinct fatigue and energy trajectories; evaluate for differences in phenotypic characteristics between the latent classes for fatigue and energy; and evaluate for associations between polymorphisms in genes for pro- and anti-inflammatory cytokines, their receptors, and their transcriptional regulators and latent class membership.

METHODS

Patients were enrolled before and followed for six months after breast cancer surgery. Latent class analyses were done to identify subgroups of patients with distinct fatigue and energy trajectories. Candidate gene analyses were done to identify cytokine genes associated with these two symptoms.

RESULTS

For both fatigue and lack of energy, two distinct latent classes were identified. Phenotypic characteristics associated with the higher fatigue class were younger age, higher education, lower Karnofsky Performance Status score, higher comorbidity, higher number of lymph nodes removed, and receipt of chemotherapy (CTX). Polymorphisms in interleukin (IL) 1β and IL10 were associated with membership in the higher fatigue class. Phenotypic characteristics associated with the lower energy class included: a lower Karnofsky Performance Status score and a higher comorbidity score. A polymorphism in IL1R1 was associated with membership in the lower energy class.

CONCLUSION

Within each latent class, the severity of fatigue and decrements in energy were relatively stable over the first six months after breast cancer surgery. Distinct phenotypic characteristics and genetic polymorphisms were associated with membership in the higher fatigue and lower energy classes.

Emerging potassium channel targets for the treatment of pain

PURPOSE OF REVIEW

Poor management of chronic pain remains a significant cause of misery with huge socioeconomic costs. Accumulating research in potassium (K+) channel physiology has uncovered several promising leads for the development of novel analgesics.

RECENT FINDINGS

We now recognize that certain K+ channel subunits are directly gated to pain-relevant stimuli (Kv1.1, K2P) whereas others are specifically modulated by inflammatory processes (Kv7, BKCA, K2P). Genetic analyses illustrate that K+ channel gene variation can predict pain sensitivity (KCNS1, GIRKs), risk for persistent pain (KCNS1, GIRKs, TRESK) and analgesic effectiveness (GIRK2). Importantly, preclinical studies confirm that K+ channel dysfunction can be a pain trigger in traumatic neuropathies (Kv9.1/Kv2.1, Kv7, Kv1.2) and migraine (TRESK). Finally, emerging data suggest that even pain in diabetes, bone cancer and autoimmune neuropathies may have K+ channel dysfunction constituents.

SUMMARY

There is a long-sought need for superior pharmacotherapy of pain syndromes. Although universal enhancement of K+ channel function in the periphery can decrease nociceptive excitability irrespective of the underlying cause, a more refined targeting of subunits with dominant nociceptive roles could yield highly efficacious treatments with fewer side-effects. The ongoing characterization of molecular interactions linking K+ channel dysfunction to pain is instrumental for identifying candidates with the most therapeutic potential.

Variations in potassium channel genes are associated with distinct trajectories of persistent breast pain after breast cancer surgery

Persistent pain after breast cancer surgery is a common clinical problem. Given the role of potassium channels in modulating neuronal excitability, coupled with recently published genetic associations with preoperative breast pain, we hypothesized that variations in potassium channel genes will be associated with persistent postsurgical breast pain. In this study, associations between 10 potassium channel genes and persistent breast pain were evaluated. Using growth mixture modeling (GMM), 4 distinct latent classes of patients, who were assessed before and monthly for 6 months after breast cancer surgery, were identified previously (ie, No Pain, Mild Pain, Moderate Pain, Severe Pain). Genotyping was done using a custom array. Using logistic regression analyses, significant differences in a number of genotype or haplotype frequencies were found between: Mild Pain vs No Pain and Severe Pain vs No Pain classes. Seven single-nucleotide polymorphisms (SNPs) across 5 genes (ie, potassium voltage-gated channel, subfamily A, member 1 [KCNA1], potassium voltage-gated channel, subfamily D, member 2 [KCND2], potassium inwardly rectifying channel, subfamily J, members 3 and 6 (KCNJ3 and KCNJ6), potassium channel, subfamily K, member 9 [KCNK9]) were associated with membership in the Mild Pain class. In addition, 3 SNPs and 1 haplotype across 4 genes (ie, KCND2, KCNJ3, KCNJ6, KCNK9) were associated with membership in the Severe Pain class. These findings suggest that variations in potassium channel genes are associated with both mild and severe persistent breast pain after breast cancer surgery. Although findings from this study warrant replication, they provide intriguing preliminary information on potential therapeutic targets.

Preoperative Breast Pain Predicts Persistent Breast Pain and Disability After Breast Cancer Surgery

CONTEXT

Approximately 30% of the women report pain in the affected breast before breast cancer surgery.

OBJECTIVES

The purpose of this secondary analysis of our prospective study was to determine how women who experienced both preoperative and persistent postsurgical breast pain (n=107) differed from women who did not report preoperative breast pain and did (n=158) or did not (n=122) experience persistent postsurgical breast pain.

METHODS

Differences in demographic and clinical characteristics were evaluated. Linear mixed effects (LME) modeling was used to evaluate for group differences in symptom severity, function, sensation, and quality of life (QOL) over time.

RESULTS

Between-group differences in demographic and clinical characteristics as well as trajectories of shoulder function and QOL were identified. Women with both preoperative and persistent postsurgical breast pain were younger; were more likely to report swelling, strange sensations, hardness, and numbness in the affected breast before surgery; and were more likely to have reconstruction at the time of surgery. Women with both preoperative and persistent postsurgical breast pain had more biopsies in the prior year, more lymph nodes removed, and reported more severe acute postsurgical pain than women without preoperative breast pain. The LME modeling revealed significant group effects for most outcomes evaluated. Over the six months of the study, women with both preoperative and persistent postsurgical pain had persistently poorer shoulder flexion and physical well-being than women without preoperative breast pain.

CONCLUSION

Investigations of the etiology and molecular mechanisms of preoperative breast pain, as well as interventions for this high-risk group, are needed.