Expression of ZKSCAN3 protein suppresses proliferation, migration, and invasion of pancreatic cancer through autophagy.

Elevated autophagy activity enhances the malignancy of pancreatic cancer (PaCa), and autophagy is recognized as a novel therapeutic target. Zinc finger protein with KRAB and SCAN domains 3 (ZKSCAN3) is a transcription factor that suppresses autophagy, but its association with PaCa is unknown. We analyzed the function of ZKSCAN3 in PaCa and investigated whether autophagy regulation through ZKSCAN3 could become a new therapeutic target for PaCa. Using reverse transcription-quantitative polymerase chain reaction and western blotting, we observed that ZKSCAN3 expression was upregulated in several PaCa cell lines compared with normal pancreatic ductal epithelial cells. Additionally, comparing ZKSCAN3 expression with the prognosis of PaCa patients using web databases, we found that higher ZKSCAN3 expression in PaCa was associated with extended overall survival. Knocking down ZKSCAN3 promoted the proliferation of PaCa cells. Moreover, following ZKSCAN3 knockdown, PaCa cells exhibited significantly enhanced migratory and invasive properties. Conversely, overexpression of ZKSCAN3 significantly suppressed the proliferation, migration and invasion of PaCa cells. Additionally, the knockdown of ZKSCAN3 increased the expression of LC3-II, a marker of autophagy, whereas ZKSCAN3 overexpression decreased LC3-II expression. In a xenograft mouse model, tumors formed by MIA PaCa-2 cells in which ZKSCAN3 was knocked down significantly increased in size compared with the control group. In conclusion, ZKSCAN3 expression was upregulated in several pancreatic cancer cells. Additionally, it was revealed that ZKSCAN3 is negatively correlated with the malignancy of PaCa through autophagy. These results suggest that autophagy regulation via ZKSCAN3 may be a new therapeutic target for PaCa.

POLArIS, a versatile probe for molecular orientation, revealed actin filaments associated with microtubule asters in early embryos.

Biomolecular assemblies govern the physiology of cells. Their function often depends on the changes in molecular arrangements of constituents, both in the positions and orientations. While recent advancements of fluorescence microscopy including super-resolution microscopy have enabled us to determine the positions of fluorophores with unprecedented accuracy, monitoring the orientation of fluorescently labeled molecules within living cells in real time is challenging. Fluorescence polarization microscopy (FPM) reports the orientation of emission dipoles and is therefore a promising solution. For imaging with FPM, target proteins need labeling with fluorescent probes in a sterically constrained manner, but because of difficulties in the rational three-dimensional design of protein connection, a universal method for constrained tagging with fluorophore was not available. Here, we report POLArIS, a genetically encoded and versatile probe for molecular orientation imaging. Instead of using a direct tagging approach, we used a recombinant binder connected to a fluorescent protein in a sterically constrained manner that can target specific biomolecules of interest by combining with phage display screening. As an initial test case, we developed POLArISact, which specifically binds to F-actin in living cells. We confirmed that the orientation of F-actin can be monitored by observing cells expressing POLArISact with FPM. In living starfish early embryos expressing POLArISact, we found actin filaments radially extending from centrosomes in association with microtubule asters during mitosis. By taking advantage of the genetically encoded nature, POLArIS can be used in a variety of living specimens, including whole bodies of developing embryos and animals, and also be expressed in a cell type/tissue specific manner.

[A Case Report of Hepatic Angiosarcoma Developed against the Background of Hepatic Hemochromatosis].

A 35-year-old man who had fever and stomachache was referred to our hospital. He underwent surgery and chemoradiotherapy for neuroblastoma as a child and subsequently developed leukemia. Frequent blood transfusions and bone marrow transplants were performed due to anemia. Abdominal contrast CT scan and contrast MRI showed tumorous lesions with a diameter of 60×42 mm in liver S6, and a tendency to increase in a short term. There was also hemochromatosis in the liver. We considered it a malignant tumor and performed a right lobectomy. Pathological examination diagnosed the tumor hepatic angiosarcoma. The postoperative course was fine and he was discharged without complications. But multiple liver metastases appeared 6 months after surgery. We performed chemotherapy but he passed away 10 months after surgery. Hepatic angiosarcoma is a rare disease among liver malignancies and has a very poor prognosis. As for the cause of hepatic angiosarcoma, many of them are unknown, but chronic exposures such as vinyl monomers have been reported in some cases. Hemochromatosis has been reported as a background factor for malignant tumors such as hepatocellular carcinoma. In this case it is possible that it contributed to the development of hepatic angiosarcoma.

[A Case of Surgical Resection of Advanced Gallbladder Cancer with Adult Annular Pancreas].

An-81-year-old man presented to another doctor complaining of epigastric pain. He was referred to us after the laboratory data revealed a high serum CEA and abdominal ultrasonography showed the space occupying lesion in the left liver. Abdominal CT revealed advanced gallbladder cancer infiltrating the liver and colon and found annular pancreas surrounding the descending portion of duodenum. We chose partial hepatectomy(S4a+S5), extrahepatic bile duct resection with hepaticojejunostomy and partial colectomy. Pathological diagnosis of the tumor was pT3N1M0, gallbladder cancer. The patient was discharged on the 21 days after operation. The frequency of malignant tumors in adult annular pancreas are not revealed. But some cases present with adult annular pancreas complicating the biliary tract tumor. We experienced a case of advanced gallbladder cancer with adult annular pancreas and report our case and review the pertinent literature.

[An Intraductal Papillary Mucinous Neoplasm of the Pancreas with Metachronous Quadruple Cancers].

The patient described herein was diagnosed with left breast, endometrial, and early gastric cancers at 49, 53, and 57 years of age, respectively. Magnetic resonance cholangiopancreatography performed when she was undergoing treatment for cholecystitis at 50 years of age showed local pancreatic duct dilatation in the pancreatic head. She was followed in the Department of Gastroenterology at our hospital for an intraductal papillary mucinous neoplasm(IPMN). An abdominal computed tomography scan obtained at 59 years of age revealed dilation of the main pancreatic duct in the pancreas body and tail, therefore an endoscopic ultrasound-guided fine needle aspiration was performed. She was diagnosed with pancreatic cancer and underwent a laparoscopic distal pancreatectomy. The postoperative course was uneventful; however, the pancreatic cancer recurred and she died approximately 14 months postoperatively. Reports of multiple cancers associated with IPMNs are rare, yet we managed a patient with a pancreatic head IPMN complicated by metachronous quadruple carcinomas( breast, endometrial, gastric, and pancreatic cancers).

Development of nanobody-based POLArIS orientation probes enabled multi-color/multi-target orientation imaging in living cells.

Fluorescence polarization microscopy (FPM) can visualize the dipole orientation of fluorescent molecules and has been used for analyzing architectural dynamics of biomolecules including cytoskeletal proteins. To monitor the orientation of target molecules by FPM, target molecules need to be labeled with fluorophores in a sterically constrained manner, so that the fluorophores do not freely rotate. Recently, a versatile probe for such labeling using fluorescent proteins, POLArIS (Probe for Orientation and Localization Assessment, recognizing specific Intracellular Structures of interest), was reported. POLArIS is a fusion protein consisting of a non-immunoglobulin-based recombinant binder Affimer and a green fluorescent protein (GFP), where the Affimer and GFP are rigidly connected to each other. POLArIS probe for molecules of interest can be developed through phage display screening of Affimer. This screening is followed by the rigid connection of fluorescent proteins to the selected Affimers. The Affimer-based POLArIS, however, cannot be used with animal immune libraries for selecting specific binder clones. In addition, multi-color FPM by POLArIS was not available due to the lack of color variations of POLArIS. In this study, we have developed new versions of POLArIS with nanobodies, which are compatible with animal immune libraries, and expanded color variations of POLArIS with cyan/green/yellow/red fluorescent proteins, enabling multi-color orientation imaging for multiple targets. Using nanobody-based POLArIS orientation probes, we performed two-color FPM of F-actin and vimentin in living cells. Furthermore, we made nanobody-based POLArIS probes that have different dipole orientations for adjusting the orientation of fluorescence polarization with respect to the target molecules. These nanobody-based POLArIS with options of colors and dipole orientations will enhance the performance of this probe for broader applications of fluorescence polarization imaging in living cells, tissues, and whole organisms.

A hybrid approach for chronic pancreatitis: combination of laparoscopic assisted distal pancreatectomy and open Frey procedure.

BACKGROUND: The treatment of chronic pancreatitis requires a surgical approach in patients who are refractory to medical therapy. During surgical treatment, ductal decompression is required, but a pancreatectomy is necessary for some patients, such as those with severe stenosis of the pancreatic duct. Indeed, suboptimal procedures lead to recurrent pancreatitis. We used a laparoscopic hybrid approach for patients with severe stenosis of the pancreatic duct. In this report, we present the feasibility and outcomes of our approach. METHODS: We selected a laparoscopic approach for the distal pancreatectomy, which is relatively safe and the effect of reducing the length of the wound is substantial. We selected an open approach for the Frey procedure because complete ductal compression has a high risk for injury to the vessels posterior to the pancreas. We recorded the operative outcomes, postoperative complications, and recurrence of pancreatitis. RESULTS: We performed the laparoscopic hybrid approach on 3patients between January and December 2018. There were no major intraoperative complications (Clavien-Dindo classification IIIa or more) and the postoperative course was uneventful in all patients. There were no recurrences of pancreatitis and no postoperative pain in all patients in > 2 years of follow-up. CONCLUSION: Our hybrid method with a focus on complete ductal compression with safety and minimal invasiveness might be the optimal approach for the surgical treatment of chronic pancreatitis that requires a pancreatectomy with the Frey procedure.

[A Case of Solitary Liver Metastasis from Renal Cell Carcinoma That Was Difficult to Distinguish from Hepatocellular Carcinoma and Underwent Laparoscopic Resection].

We experienced a case of solitary liver tumor that developed after renal cancer surgery. Before the surgery, the tumor was suspected to be hepatocellular carcinoma and was subsequently diagnosed as renal cancer liver metastasis. An 81-year-old man underwent retroperitoneal laparoscopic nephrectomy for left renal cancer in January 2017. After that, the cancer had not recurred, but a follow-up CT examination 1 year after the operation revealed a 42 mm-sized tumor in the liver S6. Liver biopsy was performed for diagnosis, but in histopathological findings, the diagnosis was difficult to make. Eventually, the preoperative final diagnosis was hepatocellular carcinoma. Laparoscopic partial hepatectomy was performed in June 2018, and in the histopathological findings of the resected specimen, the final diagnosis was the liver metastasis from renal cancer. Generally, the prognosis of renal cancer with liver metastasis is poor, but if complete resection is possible, it is recommended in the Clinical Practical Guideline for Renal Cancer. In recent years, the number of minimally invasive laparoscopic surgeries for hepatectomy has increased, and its safety has also improved. Therefore, resection is diagnostic treatment for cases where, like this case, preoperative diagnosis for solitary liver tumor is difficult. Laparoscopic hepatectomy could be one of the effective treatment strategies.

Epithelial cyst arising in an intrapancreatic accessory spleen: a case report of robotic surgery and review of minimally invasive treatment.

BACKGROUND: An epithelial cyst in an intrapancreatic accessory spleen (ECIPAS) is rare. We report a case of ECIPAS that was treated with robot-assisted distal pancreatectomy with splenectomy. CASE PRESENTATION: The case was a 59-year-old woman who was referred to our hospital after a pancreatic tail tumor was found on computed tomography prior to surgery for small bowel obstruction at another hospital. A cystic lesion in the pancreatic tail was discovered and evaluated by magnetic resonance imaging and endoscopic ultrasonography. Based on clinical and radiological features, mucinous cystic neoplasm was included in the differential diagnosis. The patient underwent robot-assisted distal pancreatectomy with splenectomy. The postoperative course was uneventful. Pathological evaluation revealed a 20-mm ECIPAS in the pancreatic tail. CONCLUSIONS: If a pancreatic tail tumor is present, ECIPAS should be included in the differential diagnosis. However, preoperative diagnosis is difficult, and a definitive diagnosis is often not obtained until after surgery. Surgery should be minimally invasive. Laparoscopic distal pancreatectomy has become a standard surgical procedure because it is minimally invasive. Robot-assisted surgery is not only minimally invasive, but also advantageous, because it has a stereoscopic magnifying effect and allows the forceps to move smoothly. Robot-assisted distal pancreatectomy may be a good option, when performing surgery for a pancreatic tail tumor.

[A Case Report of Lymph Node Metastasis of Hepatocellular Carcinoma Resected by Laparoscopic Surgery].

The case presented is a 72-year-old male with no history of hepatitis B or C. Dynamic CT revealed a 2 cm mass in the liver (S8), with arterial phase hyperenhancement and delayed phase washout. The patient underwent an open S8 subsegmentectomy. The mass was pathologically diagnosed as well-to-moderately differentiated hepatocellular carcinoma(T2N0M0, Stage Ⅱ). At 2 years 10 months postoperatively, MRI showed a 4 cm mass in contact with the pancreatic head, inferior vena cava, and duodenum. The mass had moderate FDG uptake on PET scan, and early phase hyperenhancement and delayed phase washout on dynamic CT. We performed laparoscopic mass resection, suspecting lymph node metastasis of the hepatocellular carcinoma, which was confirmed by the pathological diagnosis. The patient has survived for 1 year without recurrence. Lymph node metastasis of hepatocellular carcinoma is rare. It is unclear whether surgical resection is feasible in such cases. Here, we report a case of lymph node metastasis of hepatocellular carcinoma resected by laparoscopic surgery.

[A Case of Gallbladder Cancer with Para-Aortic Lymph Node Metastasis Successfully Treated by Gemcitabine plus Cisplatin Combination Chemotherapy and Conversion Surgery].

The case is a 59-year-old woman. A medical examination revealed a high CA19-9, she visited a nearby hospital. Abdominal echo showed thickening of the gallbladder wall, and she was referred to our hospital for further examination. EUS-FNA was performed and a biopsy of #12 lymph node revealed undifferentiated cancer, which was diagnosed as gallbladder cancer. FDG-PET showed accumulation of FDG in the gallbladder lumen and swollen lymph nodes around the aorta. Therefore, the cancer was considered unresectable and chemotherapy was performed. FDG-PET was re-examined after 4 courses of gemcitabine plus cisplatin combination chemotherapy. As a result, the lymph node swelling contracted, the accumulation of FDG disappeared, and surgery was scheduled. Extended cholecystectomy and extrahepatic bile duct resection were performed. She was discharged 22 days after the surgery without complications. Histopathological examination showed fibrotic tissue at the gallbladder and lymph nodes, but no residual tumor cells. There are no recurrences 11 months after surgery. Although the prognosis of gallbladder cancer with para-aortic lymph node metastasis is generally poor, it is suggested that conversion surgery with multimodality treatment including preoperative chemotherapy may be a useful therapeutic strategy.

[A Case of Unresectable Hilar Cholangiocarcinoma Resected Curatively Through Effective Response to Neoadjuvant Chemotherapy].

A 60's man came to our hospital for jaundice. Contrast-enhanced CT showed irregular thickening of the hilar bile duct, and the lymph nodes(LN)were swollen from the hilar to the abdominal aorta. These LNs showed similar findings in endoscopic ultrasonography(EUS), and fine needle aspiration cytology(FNA)was performed on the enlarged No.13LN to diagnose LN metastasis of hilar cholangiocarcinoma. Since the peri-aortic LN was also markedly enlarged, it was considered to be metastasis, and was diagnosed as unresectable hilar cholangiocarcinoma with distant LN metastasis. When gemcitabine/cisplatin therapy(GC therapy)was started, tumor markers normalized and LN decreased in 4 months. We performed GC therapy for a total of 12 cycles and did not re-exacerbate. Cholangioscopy revealed that bile duct stenosis at the hilar portion had improved. We have determined that curative resection is possible and performed surgery. We confirmed that No.16b1LN was negative by pathological diagnosis during surgery and performed left hepatic caudate lobectomy, extrahepatic cholangectomy, and biliary reconstruction. Diagnosis was pT2aN1(n8a)M0, fStage ⅢB, and pR0. After surgery, adjuvant chemotherapy with S-1 was continued.

[A Case with Long Survival after Total Remnant Pancreatectomy for Recurrence of Pancreatic Body Cancer].

A 56-year-old man underwent distal pancreatectomy due to pancreatic body carcinoma in 2009, at the age of 46. There had been no sign of metastasis and recurrence until levels of tumor markers began to increase in January 2014. PET scan, CT scan, and other examinations showed a possible carcinoma in the pancreas head. The patient underwent total remnant pancreatectomy. The tumor was located in the uncinate process of the pancreas with infiltration of the portal vein. The pathological diagnosis of the tumor was moderately differentiated adenocarcinoma. The ductal lumen structure was relatively maintained and the cytoplasm was comparatively clear. Since its pathological findings were similar to those observed in 2009, the tumor appeared to be a recurrence of the tumor resected at that time. The patient had received postoperative chemotherapy and remains alive in 2019 without recurrence. While there is evidence that surgical resection for the recurrence of other cancers such as colon cancer may improve patient survival, it remains unclear if surgical resection of recurrence in the remnant pancreas after pancreatectomy of pancreatic cancer is feasible. We report a case with long survival after surgical resection of a pancreatic carcinoma recurrence in the remnant pancreas.

[A Case of Conversion Surgery for an Initially Locally Advanced Unresectable Pancreatic Cancer after S-1 Chemotherapy].

We report a case of conversion surgery for a locally advanced unresectable(UR-LA)pancreatic cancer that was radically resected after S-1 therapy. A 65-year-old man visited a referral physician because of fatigue and liver dysfunction. A CT scan revealed a mass in the pancreatic uncinate process that was suspected to be superior mesenteric artery(SMA)infiltration and was diagnosed as UR-LA pancreatic cancer. GEM nab-PTX therapy was initiated but was discontinued after 2 courses because of adverse events. The treatment was switched to S-1 monochemotherapy. After that, the tumor did not progress for around 1.5 years, and the patient was referred to our hospital for surgical treatment. As the contact between the tumor and the SMA was considered to be less than half-round, we made a diagnosis of borderline resectable(BR-A)pancreatic cancer. Subsequently, we performed a pancreaticoduodenectomy with partial resection of the portal vein and achieved R0 resection. The patient received adjuvant chemotherapy with S-1 and showed no signs of recurrence for 10 months after surgery.

Xanthohumol inhibits angiogenesis by suppressing nuclear factor-κB activation in pancreatic cancer.

Xantohumol, a prenylated chalcone from hops (Humulus lupulus L.), has been shown to inhibit proliferation in some cancers. However, little is known regarding the effects of xanthohumol in pancreatic cancer. We have previously reported that activation of the transcription factor nuclear factor-κB (NF-κB) plays a key role in angiogenesis in pancreatic cancer. In this study, we investigated whether xanthohumol inhibited angiogenesis by blocking NF-κB activation in pancreatic cancer in vitro and in vivo. We initially confirmed that xanthohumol significantly inhibited proliferation and NF-κB activation in pancreatic cancer cell lines. Next, we demonstrated that xanthohumol significantly suppressed the expression of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8) at both the mRNA and protein levels in pancreatic cancer cell lines. We also found that coculture with BxPC-3 cells significantly enhanced tube formation in human umbilical vein endothelial cells, and treatment with xanthohumol significantly blocked this effect. In vivo, the volume of BxPC-3 subcutaneous xenograft tumors was significantly reduced in mice treated with weekly intraperitoneal injections of xanthohumol. Immunohistochemistry revealed that xanthohumol inhibited Ki-67 expression, CD31-positive microvessel density, NF-κB p65 expression, and VEGF and IL-8 levels. Taken together, these results showed, for the first time, that xanthohumol inhibited angiogenesis by suppressing NF-κB activity in pancreatic cancer. Accordingly, xanthohumol may represent a novel therapeutic agent for the management of pancreatic cancer.

Small RNA Esr41 inversely regulates expression of LEE and flagellar genes in enterohaemorrhagic Escherichia coli.

Enterohaemorrhagic Escherichia coli (EHEC) is a life-threatening human pathogen worldwide. The locus of enterocyte effacement (LEE) in EHEC encodes a type three secretion system and effector proteins, all of which are essential for bacterial adherence to host cells. When LEE expression is activated, flagellar gene expression is down-regulated because bacterial flagella induce the immune responses of host cells at the infection stage. Therefore, this inverse regulation is also important for EHEC infection. We report here that a small regulatory RNA (sRNA), Esr41, mediates LEE repression and flagellar gene activation. Multiple copies of esr41 abolished LEE expression by down-regulating the expression of ler and pch, which encode positive regulators of LEE. This regulation led to reduced EHEC adhesion to host cells. Translational gene-reporter fusion experiments revealed that Esr41 regulates ler expression at a post-transcriptional level, and pch transcription, probably via an unknown target of Esr41. Esr41-mediated ler and pch repression was not observed in cells lacking hfq, which encodes an RNA-binding protein essential for most sRNA functions, indicating that Esr41 acts in an Hfq-dependent manner. We previously reported an increase in cell motility induced by Esr41. This motility enhancement was also observed in EHEC lacking ler, showing that Esr41-mediated enhancement of cell motility is in a ler-independent manner. In addition, Esr41 activated the expression of flagellar Class 3 genes by indirectly inducing the transcription of fliA, which encodes the sigma factor for flagellar synthesis. These results suggest that Esr41 plays important roles in the inverse regulation of LEE and flagellar gene expression.

Expanded palette of Nano-lanterns for real-time multicolor luminescence imaging.

Fluorescence live imaging has become an essential methodology in modern cell biology. However, fluorescence requires excitation light, which can sometimes cause potential problems, such as autofluorescence, phototoxicity, and photobleaching. Furthermore, combined with recent optogenetic tools, the light illumination can trigger their unintended activation. Because luminescence imaging does not require excitation light, it is a good candidate as an alternative imaging modality to circumvent these problems. The application of luminescence imaging, however, has been limited by the two drawbacks of existing luminescent protein probes, such as luciferases: namely, low brightness and poor color variants. Here, we report the development of bright cyan and orange luminescent proteins by extending our previous development of the bright yellowish-green luminescent protein Nano-lantern. The color change and the enhancement of brightness were both achieved by bioluminescence resonance energy transfer (BRET) from enhanced Renilla luciferase to a fluorescent protein. The brightness of these cyan and orange Nano-lanterns was ∼20 times brighter than wild-type Renilla luciferase, which allowed us to perform multicolor live imaging of intracellular submicron structures. The rapid dynamics of endosomes and peroxisomes were visualized at around 1-s temporal resolution, and the slow dynamics of focal adhesions were continuously imaged for longer than a few hours without photobleaching or photodamage. In addition, we extended the application of these multicolor Nano-lanterns to simultaneous monitoring of multiple gene expression or Ca(2+) dynamics in different cellular compartments in a single cell.

[A Methotrexate-Associated Malignant Lymphoma with Laparoscopic Resection of the Pericardium].

We report a case of a malignant lymphoma that was treated with laparoscopic resection of the pericardium. A 43-year-old woman was diagnosed with asymptomatic extrahepatic nodule by medical examination. CT, MRI, and PET-CT examination indicated a solitary fibrous tumor(SFT). Therefore, we performed laparoscopic resection for definitive diagnosis and treatment. The tumor was located in the upper abdominal wall and adhered to the liver; hence, we additionally performed partial resection of the liver. Thereafter, we dissected the tumor from the abdominal wall alongwith a part of the diaphragm. Because intraoperative pathological examination revealed more malignancy than was preoperatively expected, we also resected a part of the pericardium. The laparoscopic approach to the pericardium can be performed safely because of its magnification effect, which is an advantage of laparoscopic surgery.

Enhancement of the CXCL12/CXCR4 axis due to acquisition of gemcitabine resistance in pancreatic cancer: effect of CXCR4 antagonists.

BACKGROUND: The CXCL12-CXCR4 signaling axis in malignant tumor biology has increased in importance, and these peptides are implicated in tumor growth, invasion and metastasis. The aim of our study was to examine the important role of the axis in pancreatic cancer (PaCa) cells' relationship with stromal cells in gemcitabine-resistant (GEM-R) tumors and to confirm the effectiveness of CXCR4 antagonists for the treatment of GEM-R PaCa cells. METHODS: We established two GEM-R PaCa cell lines using MIA PaCa-2 and AsPC-1 cells. The expression of CXCR4 mRNA in PaCa cells and the expression of CXCL12 mRNA in fibroblasts were examined by reverse transcription polymerase chain reaction (RT-PCR). The expression of CXCR4 protein in PaCa cells was examined by immunosorbent assay (ELISA) and immunocytochemistry. Using Matrigel invasion assays and animal studies, we then examined the effects of two CXCR4 antagonists, AMD11070 and KRH3955, on the invasiveness and tumorigenicity of GEM-R PaCa cells stimulated by CXCL12. RESULTS: We found that the expression of CXCR4 in GEM-R PaCa cells was significantly enhanced by GEM but not in normal GEM-sensitive (GEM-S) PaCa cells. In RT-PCR and ELISA assays, the production and secretion of CXCL12 from fibroblasts was significantly enhanced by co-culturing with GEM-R PaCa cells treated with GEM. In Matrigel invasion assays, the invasiveness of GEM-R PaCa cells treated with GEM was significantly activated by fibroblast-derived CXCL12 and was significantly inhibited by CXCR4 antagonists, AMD11070 and KRH3955. In vivo, the tumorigenicity of GEM-R PaCa cells was activated by GEM, and it was significantly inhibited by the addition with CXCR4 antagonists. CONCLUSIONS: Our findings demonstrate that the CXCL12-CXCR4 signaling axis plays an important role in PaCa cells' resistance to GEM. CXCR4 expression was significantly enhanced by the exposure to GEM in GEM-R PaCa cells but not in GEM-S PaCa cells. Furthermore, CXCR4 antagonists can inhibit the growth and invasion of GEM-R PaCa cells. These agents may be useful as second-line chemotherapy for GEM-R PaCa in the future.