Pain control by ionizing radiation of bone metastasis

Pain treatment due to cancer is a large fraction of the care in a radiotherapy department. While radiation treatment is very effective in reducing pain, the pathophysiology of bone metastases remains very complex. Reducing the number of tumour cells by radiation will reduce the pressure in bone marrow, but the very rapid response to radiation treatment seen in some patients is probably related to the presence of highly radiosensitive inflammatory cells. In this review we give an overview of the pathophysiological mechanisms which lead to pain associated with bone metastasis and the impact of radiation treatment and other treatments on this mechanism.     

SIRT1 activation by SRT1720 attenuates bone cancer pain via preventing Drp1-mediated mitochondrial fission

Bone cancer pain (BCP) is the pain induced by primary bone cancer or tumor metastasis. Increasing evidence and our previous studies have shown that mammalian silent information regulator 2?homolog (SIRT1) is involved in periphery sensitization and central sensitization of BCP, and the underlying mechanism of SIRT1 in bone cancer pain may provide clues for pain treatment. Dynamin-related protein 1 (Drp1) is an essential regulator for mitochondrial fission. In this research, BCP model rats were established by injecting MRMT-1 rat mammary gland carcinoma cells into the left tibia of female Sprague-Dawley rats and validated by tibia radiographs, histological examination and mechanical pain test. As a result BCP rats exhibited bone destruction and sensitivity mechanical pain. BCP increased inflammatory cells infiltration and apoptosis, reduced SIRT1 protein expression and phosphorylation, and elevated Drp1 expression in spinal cord. An agonist of SIRT1 named SRT1720 intrathecal treatment in BCP rats increased SIRT1 phosphorylation, reduced the up-regulated Drp1 expression, and reversed pain behavior. SRT1720 also regulated Bcl-2/BAX and cleaved caspase-3 expressions, and inhibited mitochondrial apoptosis in spinal cord of BCP rats. For in vitro research, SRT1720 treatment decreased Drp1 expression in a dose-dependent manner, blocked CCCP-induced mitochondrial membrane potential change, consequently reduced apoptosis and promoted proliferation. These data suggest that SIRT1 activation by SRT1720 attenuated bone cancer pain via preventing Drp1-mediated mitochondrial fission. Our results provide new targets for therapeutics of bone cancer pain.     

Curcumin induces radiosensitivity of in vitro and in vivo cancer models by modulating pre-mRNA processing factor 4 (Prp4)

Radiation therapy plays a central role in adjuvant strategies for the treatment of both pre- and post-operative human cancers. However, radiation therapy has low efficacy against cancer cells displaying radio-resistant phenotypes. Ionizing radiation has been shown to enhance ROS generation, which mediates apoptotic cell death. Further, concomitant use of sensitizers with radiation improves the efficiency of radiotherapy against a variety of human cancers. Here, the radio-sensitizing effect of curcumin (a derivative of turmeric) was investigated against growth of HCT-15 cells and tumor induction in C57BL/6J mice. Ionizing radiation induced apoptosis through ROS generation and down-regulation of Prp4K, which was further potentiated by curcumin treatment. Flow cytometry revealed a dose-dependent response for radiation-induced cell death, which was remarkably reversed by transfection of cells with Prp4K clone. Over-expression of Prp4K resulted in a significant decrease in ROS production possibly through activation of an anti-oxidant enzyme system. To elucidate an integrated mechanism, Prp4K knockdown by siRNA ultimately restored radiation-induced ROS generation. Furthermore, B16F10 xenografts in C57BL/6J mice were established in order to investigate the radio-sensitizing effect of curcumin in vivo. Curcumin significantly enhanced the efficacy of radiation therapy and reduced tumor growth as compared to control or radiation alone. Collectively, these results suggest a novel mechanism for curcumin-mediated radio-sensitization of cancer based on ROS generation and down-regulation of Prp4K.     

Autophagy provides a conceptual therapeutic framework for bone metastasis from prostate cancer

Prostate cancer is a common malignant tumor, which can spread to multiple organs in the body. Metastatic disease is the dominant reason of death for patients with prostate cancer. Prostate cancer usually transfers to bone. Bone metastases are related to pathologic fracture, pain, and reduced survival. There are many known targets for prostate cancer treatment, including androgen receptor (AR) axis, but drug resistance and metastasis eventually develop in advanced disease, suggesting the necessity to better understand the resistance mechanisms and consider multi-target medical treatment. Because of the limitations of approved treatments, further research into other potential targets is necessary. Metastasis is an important marker of cancer development, involving numerous factors, such as AKT, EMT, ECM, tumor angiogenesis, the development of inflammatory tumor microenvironment, and defect in programmed cell death. In tumor metastasis, programmed cell death (autophagy, apoptosis, and necroptosis) plays a key role. Malignant cancer cells have to overcome the different forms of cell death to transfer. The article sums up the recent studies on the mechanism of bone metastasis involving key regulatory factors such as macrophages and AKT and further discusses as to how regulating autophagy is crucial in relieving prostate cancer bone metastasis.Subject terms: Cancer models, Prostate cancer     

Lysine-Specific Demethylase 1 in Breast Cancer Cells Contributes to the Production of Endogenous Formaldehyde in the Metastatic Bone Cancer Pain Model of Rats

Background

Bone cancer pain seriously affects the quality of life of cancer patients. Our previous study found that endogenous formaldehyde was produced by cancer cells metastasized into bone marrows and played an important role in bone cancer pain. However, the mechanism of production of this endogenous formaldehyde by metastatic cancer cells was unknown in bone cancer pain rats. Lysine-specific demethylase 1 (LSD1) is one of the major enzymes catalyzing the production of formaldehyde. The expression of LSD1 and the concentration of formaldehyde were up-regulated in many high-risk tumors.

Objective

This study aimed to investigate whether LSD1 in metastasized MRMT-1 breast cancer cells in bone marrows participated in the production of endogenous formaldehyde in bone cancer pain rats.

Methodology/Principal Findings

Concentration of the endogenous formaldehyde was measured by high performance liquid chromatography (HPLC). Endogenous formaldehyde dramatically increased in cultured MRMT-1 breast cancer cells in vitro, in bone marrows and sera of bone cancer pain rats, in tumor tissues and sera of MRMT-1 subcutaneous vaccination model rats in vivo. Formaldehyde at a concentration as low as the above measured (3 mM) induced pain behaviors in normal rats. The expression of LSD1 which mainly located in nuclei of cancer cells significantly increased in bone marrows of bone cancer pain rats from 14 d to 21 d after inoculation. Furthermore, inhibition of LSD1 decreased the production of formaldehyde in MRMT-1 cells in vitro. Intraperitoneal injection of LSD1 inhibitor pargyline from 3 d to 14 d after inoculation of MRMT-1 cancer cells reduced bone cancer pain behaviors.

Conclusion

Our data in the present study, combing our previous report, suggested that in the endogenous formaldehyde-induced pain in bone cancer pain rats, LSD1 in metastasized cancer cells contributed to the production of the endogenous formaldehyde.     

Pamidronate in the treatment of bone metastases from breast cancer

Bone metastases afflict over 70% of patients with advanced breast cancer, resulting in impaired quality of life and significant clinical problems. Until appearance of the bisphosphonates there was no specific therapeutic treatment available to manage the symptoms of osteolytic bone metastases. Bisphosphonates are stable chemical analogues of pyrophosphate, and inhibit osteoclast-mediated bone resorption, the treatment is effective in reducing skeletal morbidity in breast cancer with fewer skeletal related events, reduced pain and analgesic consumption, and improved quality of life. As a result, bisphosphonates should now be part of the routine management of metastatic bone disease and multiple myeloma. Promising data have resulted in considerable interest in the possible adjuvant use of bisphosphonates. Pamidronate is an easy to use potent inhibitor of osteolysis, given in conjunction with standard anticancer therapies effectively relieves bone pain and improves performance status. Monthly pamidronate infusions for one or two years in addition to standard anticancer therapy reduce by more than one third the yearly frequency of skeletal-related events. The authors report their practice in which 119 breast cancer patients metastatic to bone received 90-120 mg pamidronate infusion/cycle in addition to standard breast cancer therapy every 3-4 weeks.     

Mechanisms of Nerve Capping Technique in Prevention of Painful Neuroma Formation

Nerve capping techniques have been introduced as a promising treatment modality for the treatment of painful neuroma with varied outcomes; however, its exact mechanism is still unknown. RhoA is one of the members of the RAS superfamily of GTPases that operate as molecular switches and plays an important role in peripheral nerve regeneration. Our aim was to investigate the structural and morphologic mechanisms by which the nerve capping technique prevents the formation of painful neuromas after neuroectomy. We also hoped to provide a theoretical basis for this treatment approach. An aligned nanofiber conduit was used for the capping procedure and the sciatic nerve of Sprague-Dawley rats was selected as the animal model. Behavioral analysis, extent of neuroma formation, histological assessment, expressions of pain markers of substance P and c-fos, molecular biological changes as well as ultrastructural features were investigated and compared with the findings in a no-capping control group. The formation of traumatic neuromas was significantly inhibited in the capping group with relatively “normal” structural and morphological features and no occurrence of autotomy and significantly lower expression of pain markers compared to the no-capping group. The gene expression of RhoA was consistently in a higher level in the capping group within 8 weeks after surgery. This study shows that capping technique will alter the regeneration state of transected nerves and reduce painful neuroma formation, indicating a promising approach for the treatment of painful neuroma. The initiation of the “regenerative brake” induced by structural as well as morphological improvements in the severed nerve is theorized to be most likely a key mechanism for the capping technique in the prevention of painful neuroma formation.     

Phase II Study of Concurrent Capecitabine and External Beam Radiotherapy for Pain Control of Bone Metastases of Breast Cancer Origin

Background

Pain from bone metastases of breast cancer origin is treated with localized radiation. Modulating doses and schedules has shown little efficacy in improving results. Given the synergistic therapeutic effect reported for combined systemic chemotherapy with local radiation in anal, rectal, and head and neck malignancies, we sought to evaluate the tolerability and efficacy of combined capecitabine and radiation for palliation of pain due to bone metastases from breast cancer.

Methodology/Principal Findings

Twenty-nine women with painful bone metastases from breast cancer were treated with external beam radiation in 10 fractions of 3 Gy, 5 fractions a week for 2 consecutive weeks. Oral capecitabine 700 mg/m² twice daily was administered throughout radiation therapy. Rates of complete response, defined as a score of 0 on a 10-point pain scale and no increase in analgesic consumption, were 14% at 1 week, 38% at 2 weeks, 52% at 4 weeks, 52% at 8 weeks, and 48% at 12 weeks. Corresponding rates of partial response, defined as a reduction of at least 2 points in pain score without an increase in analgesics consumption, were 31%, 38%, 28%, 34% and 38%. The overall response rate (complete and partial) at 12 weeks was 86%. Side effects were of mild intensity (grade I or II) and included nausea (38% of patients), weakness (24%), diarrhea (24%), mucositis (10%), and hand and foot syndrome (7%).

Conclusions/Significance

External beam radiation with concurrent capecitabine is safe and tolerable for the treatment of pain from bone metastases of breast cancer origin. The overall and complete response rates in our study are unusually high compared to those reported for radiation alone. Further evaluation of this approach, in a randomized study, is warranted.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01784393","term_id":"NCT01784393"}}NCT01784393{"type":"clinical-trial","attrs":{"text":"NCT01784393","term_id":"NCT01784393"}}NCT01784393     

Studies on the analgesic activities of Jia-Yuan-Qing pill and its safety evaluation in mice

The analgesic activity of Porcellio laevis Latreille, Rhizoma Corydalis, and Radix Cynanchi Paniculati have been reported in recent years. A new formula named Jia-Yuan-Qing pill (JYQP) is therefore created by combining the three herbs at 9:7:7 ratio according to traditional Chinese theories. The present study aims to evaluate the effect of JYQP as a novel painkiller in various models. Acute toxicity test was applied to evaluate the safety of JYQP. Acetic-acid-induced writhing, hot plate test, formalin test, and naloxone-pretreated writhing test were employed to elaborate the analgesic activity of JYQP and its possible mechanism. A bone cancer pain mouse model was performed to further assess the effect of JYQP in relieving cancer pain. Test on naloxone-precipitated withdrawal symptoms was conduct to examine the physical dependence of mice on JYQP. Data revealed that JYQP reduced writhing and stretching induced by acetic acid; however, this effect could not be blocked by naloxone. JYQP specifically suppressed the phase II reaction time in formalin-treated mice; meanwhile, no analgesic effect of JYQP in hot plate test was observed, indicating that JYQP exerts analgesic activity against inflammatory pain rather than neurogenic pain. Furthermore, JYQP could successfully relieve bone cancer pain in mice. No physical dependence could be observed upon long-term administration in mice. Collectively, our present results provide experimental evidence in supporting clinical use of JYQP as an effective and safe agent for pain treatment.     

Osteoprotegerin blocks bone cancer-induced skeletal destruction, skeletal pain and pain-related neurochemical reorganization of the spinal cord

Bone cancer pain is common among cancer patients and can have a devastating effect on their quality of life. A chief problem in designing new therapies for bone cancer pain is that it is unclear what mechanisms drive this distinct pain condition. Here we show that osteoprotegerin, a secreted 'decoy' receptor that inhibits osteoclast activity, also blocks behaviors indicative of pain in mice with bone cancer. A substantial part of the actions of osteoprotegerin seems to result from inhibition of tumor-induced bone destruction that in turn inhibits the neurochemical changes in the spinal cord that are thought to be involved in the generation and maintenance of cancer pain. These results demonstrate that excessive tumor-induced bone destruction is involved in the generation of bone cancer pain and that osteoprotegerin may provide an effective treatment for this common human condition.     

2-溴棕榈酸调节背根神经节中ASIC3蛋白的膜定位缓解大鼠骨癌痛

骨癌痛（BCP）是恶性肿瘤患者最常见的疼痛之一,严重影响患者的生活质量。BCP的分子作用机制和新药研发都迫在眉睫。2-溴棕榈酸（2-BP）作为一种蛋白质棕榈化抑制剂在病理性疼痛中有镇痛效果,而在骨癌痛中作用仍不清楚。酸敏感离子通道3型（ASIC3）,作为一个重要的疼痛因子能否受到2-BP的调控也未知。为了检测2-BP在骨癌痛中的作用,并研究其对背根神经节（DRG）中ASIC3的调控,本文开展了相关工作。1）首先建立BCP大鼠模型,将大鼠乳腺癌细胞（MRMT-1）注射入雌大鼠胫骨骨髓腔内,21 d后通过X射线和机械痛检测,发现与假性手术组相比,BCP模型大鼠的胫骨被破坏;同时,BCP组大鼠的机械疼痛值明显上升（假性手术组PWT vs. BCP PWT:16.1 ± 1.5 vs. 5.3 ± 1.5; P<0.01）;表明大鼠乳腺癌骨转移疼痛模型成功构建。2）蛋白质免疫印迹检测结果显示,与正常和假性手术组相比,BCP大鼠L4-L6 DRG中酸敏感离子通道3蛋白表达上调（0.63 ± 0.03, 0.64 ± 0.1 和 1.07 ± 0.05）。3）在术后第21 d,给BCP大鼠腹腔注射2-BP,发现给药组BCP大鼠的机械疼痛值下调 （6 h后,PWT 对照 vs. PWT 2-BP: 6.9 ± 2.0 vs. 10.8 ± 1.6, P<0.01）,表明2-BP在骨癌痛模型大鼠中具有镇痛作用。4）蛋白质免疫印迹结果显示,与给药前相比,2-BP处理后降低了BCP大鼠L4-L6 DRG中膜上ASIC3蛋白的表达（1.05 ± 0.13, 0.66 ± 0.12）。同时,在ASIC3介导的酸痛模型中,2-BP给药降低大鼠震颤的次数（对照组为27 ± 1.8次,2-BP组为10 ± 1.5次）,表明2-BP给药阻断ASIC3介导的酸痛。5）在ASIC3转染的SH-SY5Y细胞中,与对照相比,2-BP给药后明显降低膜上ASIC3蛋白表达量（1.0 ± 0.2, 0.58 ± 0.10）。这些结果表明,2-BP在骨癌痛中具有镇痛作用,其镇痛机制涉及到调控背根神经节中膜上酸敏感离子通道3的表达。     

Induction of micronuclei by 153Sm-EDTMP in peripheral blood lymphocytes of patients with bone metastases.

The purpose of this study was to evaluate the degree of cytological radiation damage to peripheral blood lymphocytes induced by 153Sm-EDTMP applied for palliation of metastatic bone pain. Blood samples from 16 patients (46-82 years old), 10 without previous radiotherapy and 6 with previous radiotherapy, were collected before and one hour after the administration of a mean activity of 41.7+/-5.8 MBq/kg of 153Sm-EDTMP. Then the lymphocytes were cultured for cytokinesis block micronucleus (MN) assay. The number of MNper binucleated cells (BC) in patients without previous radiotherapy before the treatment was of 0.030 (+/- 0.016) and after one hour 0.035 (+/- 0.013), although we could find inter individual differences. The basal MN/BC of the patients with no previous radiotherapy was similar to the controls. The increment in the percentage of BC with MN was similar in patients with and without previous radiotherapy. The observed mean of MN/BC is equivalent to a dose range of 0.05 to 0.10 Gy of 153Sm-EDTMP in vitro. The relatively low frequency of lymphocyte with micronuclei after the exposure to 153Sm-EDTMP supported the contention that radiation damage in lymphocytes of patients with painful bone metastases is minimal.     

Internal radiotherapy of painful bone metastases

Internal radiotherapy is effective in the treatment of metastatic bone pain and can improve quality of life. A number of controlled studies using various agents have shown a mean response rate in pain relief of 70–80% of treated patients. Some investigators prefer radionuclides which emit low beta particles for the treatment of bone pain, because the assumption of lower bone marrow toxicity of this agents. However, neither dosimetric data for radiation absorbed dose to the bone marrow nor clinical blood count depression have shown any significant differences between these agents. Other researchers suggest enhanced antitumoral effects using high-energy beta emitters and propose aggressive first-line treatment in the early disease stage instead of using these radiopharmaceuticals only in end-stage patients suffering intractable bone pain. Another approach consists of including other treatment modalities such as autologous stem cell rescue or in combination with chemo or bisphosphonate therapy to a radionuclide treatment scheme. Future research should focus more on the curative effects of combination with radiosensitizer, for example, chemotherapy, or repeated treatments with bone seeking agents.     

Anti--Histaminic potentila of fractions from Hedranthera Barteri [(Hook F.) Pichon] root in laboratory rodents

Hedranthera barteri, anti-inflammatory activity, anti-nociceptive activity, anti-histaminic activityL. (HB) is used in the treatment of painful conditions and oedema amongst its folkloric use. The hexane and ethyl acetate fractions of the root of H. barteri were investigated for anti-nociceptive and antiinflammatory properties and probable mechanism of action. Hot plate, tail flick, formalin-induced oedema and acetic acidinduced writhing tests were employed to investigate the anti-nociceptive activity while the anti-inflammatory activity was investigated using carrageenan-induced paw oedema. Anti-histaminic potential of HB root extracts on the rat peritoneal mast cells (RPMCs) was explored through pectrofluorometric method. The root was screened for its phytochemical components. The HB root contains alkaloids,cardenolides and saponins. HXHBR exhibited higher anti-inflammatory potentials (P <0.001). HXHBR dose-dependently (P <0.01) reduced the histamine release from the rat peritoneal mast cells which is comparable with a standard anti-histaminic drug, ketotifen. These results showed that EAHBR and HXHBR possess anti-nociceptive and anti-inflammatory activities, and suggested its mechanism of action through the inhibition of histamine, an inflammatory mediator, usually released during the early phase of allergic responses and chronic phase of inflammatory pain. Flavonoids, alkaloids and/or saponins present in HB root may be responsible for its anti-nociceptive and anti-inflammatory properties.     

The doctor's dilemma: opiate analgesics and chronic pain

Opiates are utilized routinely and effectively as a short-term analgesic treatment for a variety of acute pain conditions such as occur following trauma, and for patients with painful terminal diseases such as cancer. Because opiate analgesics are highly addictive substances, their use in the treatment of chronic nonmalignant pain remains controversial.     

Static mechanical allodynia (SMA) is a paradoxical painful hypo-aesthesia: observations derived from neuropathic pain patients treated with somatosensory rehabilitation

The present study aimed at investigating the time span it takes to remove a static mechanical allodynia (SMA) in humans suffering from chronic peripheral neuropathic pain. Forty-three subjects were included in the study and, during somatosensory rehabilitation, their SMA territory was precisely mapped. They then underwent distant vibrotactile counter stimulation (DVCS) treatment. It was observed that, with DVCS, SMA disappeared in all cases, and was transformed into an underlying hypoaesthesia. It was found that the "tenderness to touch" symptom (which is SMA) was located in the same territory as the underlying hypoaesthesia, which was located on a part of the cutaneous territory of a partially damaged nerve. These results demonstrate that treating patients suffering from neuropathic pain with DVCS revealed a skin territory of denervation that was previously masked by SMA. Thus, SMA can be considered as a paradoxical painful hypoaesthesia. Furthermore, mapping SMA is a valuable source of information for our understanding of abnormal sensory processing in neuropathic pain patients. We conclude that the mapping of the zone of hypersensitivity on the skin in humans suffering from chronic peripheral neuropathic pain improves diagnosis. The mapping of the zone of hypersensitivity is a tool to presume which branch of the peripheral nerve is damaged. The location of the axonal lesions is at the periphery, while the mechanism of pain sensitization is probably central and referred peripherally to the skin by a painful hypoaesthesia.     

A cannabinoid 2 receptor agonist attenuates bone cancer-induced pain and bone loss

AimsCannabinoid CB₂ agonists have been shown to alleviate behavioral signs of inflammatory and neuropathic pain in animal models. AM1241, a CB₂ agonist, does not demonstrate central nervous system side effects seen with CB₁ agonists such as hypothermia and catalepsy. Metastatic bone cancer causes severe pain in patients and is treated with analgesics such as opiates. Recent reports suggest that sustained opiates can produce paradoxical hyperalgesic actions and enhance bone destruction in a murine model of bone cancer. In contrast, CB₂ selective agonists have been shown to reduce bone loss associated with a model of osteoporosis. Here we tested whether a CB₂ agonist administered over a 7 day period inhibits bone cancer-induced pain as well as attenuates cancer-induced bone degradation.Main methodsA murine bone cancer model was used in which osteolytic sarcoma cells were injected into the intramedullary space of the distal end of the femur. Behavioral and radiographic image analysis was performed at days 7, 10 and 14 after injection of tumor cells into the femur.Key findingsOsteolytic sarcoma within the femur produced spontaneous and touch evoked behavioral signs of pain within the tumor-bearing limb. The systemic administration of AM1241 acutely or for 7 days significantly attenuated spontaneous and evoked pain in the inoculated limb. Sustained AM1241 significantly reduced bone loss and decreased the incidence of cancer-induced bone fractures.SignificanceThese findings suggest a novel therapy for cancer-induced bone pain, bone loss and bone fracture while lacking many unwanted side effects seen with current treatments for bone cancer pain.     

Retracted: CXCL12/CXCR4 chemokine signaling in spinal glia induces pain hypersensitivity through MAPKs‐mediated neuroinflammation in bone cancer rats

The activation of MAPK pathways in spinal cord and subsequent production of proinflammatory cytokines in glial cells contribute to the development of spinal central sensitization, the basic mechanism underlying bone cancer pain (BCP). Our previous study showed that spinal CXCL12 from astrocytes mediates BCP generation by binding to CXCR4 in both astrocyters and microglia. Here, we verified that CXCL12/CXCR4 signaling contributed to BCP through a MAPK‐mediated mechanism. In naïve rats, a single intrathecal administration of CXCL12 considerably induced pain hyperalgesia and phosphorylation expression of spinal MAPK members (including extracellular signal‐regulated kinase, p38, and c‐Jun N‐terminal kinase), which could be partially prevented by pre‐treatment with CXCR4 inhibitor AMD3100. This CXCL12‐induced hyperalgesia was also reduced by MAPK inhibitors. In bone cancer rats, tumor cell inoculation into the tibial cavity caused prominent and persistent pain hyperalgesia, and associated with up‐regulation of CXCL12 and CXCR4, activation of glial cells, phosphorylation of MAPKs, and production of proinflammatory cytokines in the spinal cord. These tumor cell inoculation‐induced behavioral and neurochemical alterations were all suppressed by blocking CXCL12/CXCR4 signaling or MAPK pathways. Taken together, these results demonstrate that spinal MAPK pathways mediated CXCL12/CXCR4‐induced pain hypersensitivity in bone cancer rats, which could be druggable targets for alleviating BCP and glia‐derived neuroinflammation.

     

Persistent pain accelerates xenograft tumor growth of breast cancer in rat

Pain occurs at all stages of the patients who suffer from cancer. Owing to surgery and bone metastasis, breast cancer patients were usually disturbed by persistent pain. However, the pain-relief-right has not been respected enough in clinical cancer treatment. Whether pain has any adverse effects on cancer development is still unclear. In order to uncover this question, we established two preclinical animal models to explore the effects of pain on the tumor. For the first model, we mimicked neuropathic pain by sciatic nerve ligation on rats with xenograft tumor subcutaneously. For the second model, we mimicked the bone cancer pain by injecting tumor cell suspension into the tibial medullary cavity of rats with xenograft tumor subcutaneously. The rats with persistent pain showed higher tumor volume and tumor weight compared with the group without pain. Interestingly, when the neuropathic pain and bone cancer pain were relieved by drug administration, both the tumor volume and tumor weight were lowered compared with the group without pain relief. In summary, our study indicated that persistent pain acted as a contributing factor to tumor growth. Moreover, the pain relief could weakened the accelerating role of pain in tumor growth. Thus, we should be paid more attention to the cancer patients with persistent pain as well as cancer treatment.