Technical Strategy for Pancreatic Body Cancers: A Raison d'etre of Distal Pancreatectomy with Portal Resection.

BACKGROUND: Advancements in multiagent chemotherapy have expanded the surgical indications for pancreatic cancer. Although pancreaticoduodenectomy (PD) with portal vein resection (PVR) has become widely adopted, distal pancreatectomy (DP) with PVR remains rarely performed because of its technical complexity. This study was designed to assess the feasibility of DP-PVR compared with PD-PVR for pancreatic body cancers, with a focus on PV complications and providing optimal reconstruction techniques when DP-PVR is necessary. METHODS: A retrospective review was conducted on consecutive pancreatic body cancer patients who underwent pancreatectomy with PVR between 2005 and 2020. An algorithm based on the anatomical relationship between the arteries and PV was used for optimal surgical selection. RESULTS: Among 119 patients, 32 underwent DP-PVR and 87 underwent PD-PVR. Various reconstruction techniques were employed in DP-PVR cases, including patch reconstruction, graft interposition, and wedge resection. The majority of PD-PVR cases involved end-to-end anastomosis. The length of PVR was shorter in DP-PVR (25 vs. 40 mm; p < 0.001). Although Clavien-Dindo ≥3a was higher in DP-PVR (p = 0.002), inpatient mortality and R0 status were similar. Complete PV occlusion occurred more frequently in DP-PVR than in PD-PVR (21.9% vs. 1.1%; p < 0.001). A cutoff value of 30 mm for PVR length was determined to be predictive of nonrecurrence-related PV occlusion after DP-PVR. The two groups did not differ significantly in recurrence or overall survival. CONCLUSIONS: DP-PVR had higher occlusion and postoperative complication rates than PD-PVR. These findings support the proposed algorithm and emphasize the importance of meticulous surgical manipulation when DP-PVR is deemed necessary.

Identification of a novel target of SETD1A histone methyltransferase and the clinical significance in pancreatic cancer.

Although histone H3K4 methyltransferase SETD1A is overexpressed in various cancer types, the molecular mechanism underlying its overexpression and its target genes in pancreatic ductal adenocarcinoma (PDAC) remain unclarified. We conducted immunohistochemical staining for SETD1A in 105 human PDAC specimens to assess the relationship between SETD1A overexpression and clinicopathological features. The function and target genes of SETD1A were investigated using human pancreatic cancer cell lines. SETD1A expression was upregulated in 51.4% of patients with PDAC and was an independent prognostic factor associated with shorter disease-free survival after resection (p < 0.05). Knockdown and overexpression of SETD1A showed that SETD1A plays a crucial role in increasing the proliferation and motility of PDAC cells. SETD1A overexpression increased tumorigenicity. RNA sequencing of SETD1A-knockdown cells revealed downregulation of RUVBL1, an oncogenic protein ATP-dependent DNA helicase gene. ChIP analysis revealed that SETD1A binds to the RUVBL1 promoter region, resulting in increased H3K4me3 levels. Knockdown of RUVBL1 showed inhibition of cell proliferation, migration, and invasion of PDAC cells, which are similar biological effects to SETD1A knockdown. High expression of both SETD1A and RUVBL1 was an independent prognostic factor not only for disease-free survival but also for overall survival (p < 0.05). In conclusion, we identified RUVBL1 as a novel downstream target gene of the SETD1A-H3K4me3 pathway. Co-expression of SETD1A and RUVBL1 is an important factor for predicting the prognosis of patients with PDAC.

A liquid biopsy signature for predicting early recurrence in patients with gastric cancer.

BACKGROUND: Gastric cancer (GC) patients who experience recurrence within the first year following surgery (early recurrence [ER]) exhibit worse prognosis. Herein, we established a microRNA-based liquid biopsy assay to predict ER in GC patients. METHODS: A comprehensive biomarker discovery was performed by analysing miRNA expression profiling in 271 primary GC tumours. Thereafter, the expression of these biomarkers was validated in 290 GC cases, which included 218 tissues and 72 pre-treatment sera, from two independent institutions. RESULTS: A panel of 8 miRNAs was identified during the initial biomarker discovery, and this panel could robustly predict ER in a tissue-based clinical cohort (area under the curve [AUC]: 0.81). Furthermore, a model combining the miRNA panel, microsatellite instability (MSI) status and tumour size exhibited superior predictive performance (AUC: 0.86), and was defined as a Prediction of Early Recurrence in GC (PERGC) signature, which was successfully validated in another independent cohort (AUC: 0.82). Finally, the PERGC signature was translated into a liquid biopsy assay (AUC: 0.81), and a multivariate regression analysis revealed this signature to be an independent predictor for ER (odds ratio: 11.20). CONCLUSION: We successfully established a miRNA-based liquid biopsy signature that robustly predicts the risk of ER in GC patients.

Surgical anatomy of the dorsal pancreatic artery: Considering embryonic development.

OBJECTIVES: The dorsal pancreatic artery (DPA) is a pancreatic branch with various anatomical variations. Previous studies mostly focused on the origin of the DPA, and its pathways and branching patterns have rarely been examined. The purpose of this study was to investigate the branching patterns and pathways of the DPA. METHODS: This study included 110 patients who underwent computed tomography scans. We examined the pathways and branching patterns of the DPA. RESULTS: The DPA was identified in 101 patients (92%), and originated from the splenic artery in 30 patients (31%), the common hepatic artery in 17 patients (17%), the celiac trunk in 10 patients (10%), the superior mesenteric artery in 27 patients (27%), the replaced right hepatic artery in 7 patients (7%), the inferior pancreaticoduodenal artery in 5 patients (5%), and other arteries in 3 patients (3%). Four distinct types of branches were identified as follows: the superior branch (32%), the inferior branch (86%), the right branch (80%), and the accessory middle colic artery (12%). Additionally, the arcs of Buhler and Riolan were observed in two patients each and their anastomotic vessels followed almost the same pathway as the DPA. CONCLUSION: A number of variations of the DPA were observed with regard to its origin and branching pattern; however, the DPA and its branches always ran along the same pathway, as summarized in Fig. 4. The anatomical information gained from this study may contribute to performing safe pancreatic resections.

GABAergic and glycinergic systems regulate ON-OFF electroretinogram by cooperatively modulating cone pathways in the amphibian retina.

The network mechanisms underlying how inhibitory circuits regulate ON- and OFF-responses (the b- and d-waves) in the electroretinogram (ERG) remain unclear. The purpose of this study was to investigate the contribution of inhibitory circuits to the emergence of the b- and d-waves in the full-field ERG in the newt retina. To this end, we investigated the effects of several synaptic transmission blockers on the amplitudes of the b- and d-waves in the ERG obtained from newt eyecup preparations. Our results demonstrated that (a) L-APB blocked the b-wave, indicating that the b-wave arises from the activity of ON-bipolar cells (BCs) expressing type six metabotropic glutamate receptors; (b) the combined administration of UBP310/GYKI 53655 blocked the d-wave, indicating that the d-wave arises from the activity of OFF-BCs expressing kainate-/AMPA-receptors; (c) SR 95531 augmented both the b- and the d-wave, indicating that GABAergic lateral inhibitory circuits inhibit both ON- and OFF-BC pathways; (d) the administration of strychnine in the presence of SR 95531 attenuated the d-wave, and this attenuation was prevented by blocking ON-pathways with L-APB, which indicated that the glycinergic inhibition of OFF-BC pathway is downstream of the GABAergic inhibition of the ON-system; and (e) the glycinergic inhibition from the ON- to the OFF-system widens the response range of OFF-BC pathways, specifically in the absence of GABAergic lateral inhibition. Based on these results, we proposed a circuitry mechanism for the regulation of the d-wave and offered a tentative explanation of the circuitry mechanisms underlying ERG formation.

Quantification of multicellular colonization in tumor metastasis using exome-sequencing data.

Metastasis is a major cause of cancer-related mortality, and it is essential to understand how metastasis occurs in order to overcome it. One relevant question is the origin of a metastatic tumor cell population. Although the hypothesis of a single-cell origin for metastasis from a primary tumor has long been prevalent, several recent studies using mouse models have supported a multicellular origin of metastasis. Human bulk whole-exome sequencing (WES) studies also have demonstrated a multiple "clonal" origin of metastasis, with different mutational compositions. Specifically, there has not yet been strong research to determine how many founder cells colonize a metastatic tumor. To address this question, under the metastatic model of "single bottleneck followed by rapid growth," we developed a method to quantify the "founder cell population size" in a metastasis using paired WES data from primary and metachronous metastatic tumors. Simulation studies demonstrated the proposed method gives unbiased results with sufficient accuracy in the range of realistic settings. Applying the proposed method to real WES data from four colorectal cancer patients, all samples supported a multicellular origin of metastasis and the founder size was quantified, ranging from 3 to 17 cells. Such a wide-range of founder sizes estimated by the proposed method suggests that there are large variations in genetic similarity between primary and metastatic tumors in the same subjects, which may explain the observed (dis)similarity of drug responses between tumors.

TEAD transcription factors are required for normal primary myoblast differentiation in vitro and muscle regeneration in vivo.

The TEAD family of transcription factors (TEAD1-4) bind the MCAT element in the regulatory elements of both growth promoting and myogenic differentiation genes. Defining TEAD transcription factor function in myogenesis has proved elusive due to overlapping expression of family members and their functional redundancy. We show that silencing of either Tead1, Tead2 or Tead4 did not effect primary myoblast (PM) differentiation, but that their simultaneous knockdown strongly impaired differentiation. In contrast, Tead1 or Tead4 silencing impaired C2C12 differentiation showing their different contributions in PMs and C2C12 cells. Chromatin immunoprecipitation identified enhancers associated with myogenic genes bound by combinations of Tead4, Myod1 or Myog. Tead4 regulated distinct gene sets in C2C12 cells and PMs involving both activation of the myogenic program and repression of growth and signaling pathways. ChIP-seq from mature mouse muscle fibres in vivo identified a set of highly transcribed muscle cell-identity genes and sites bound by Tead1 and Tead4. Although inactivation of Tead4 in mature muscle fibres caused no obvious phenotype under normal conditions, notexin-induced muscle regeneration was delayed in Tead4 mutants suggesting an important role in myogenic differentiation in vivo. By combining knockdown in cell models in vitro with Tead4 inactivation in muscle in vivo, we provide the first comprehensive description of the specific and redundant roles of Tead factors in myogenic differentiation.

Loss of KDM6A characterizes a poor prognostic subtype of human pancreatic cancer and potentiates HDAC inhibitor lethality.

Although genomic analysis have recently discovered the malignant subtype of human pancreatic ductal adenocarcinoma (PDAC) characterized by frequent mutations of histone demethylase KDM6A, the biological and molecular roles still remain obscure. We herein elucidated the clinical and biological impacts of KDM6A deficiency on human PDAC and identified the therapeutic potential by pathological and molecular evaluation. Immunohistochemical analysis suggested that loss of KDM6A in cancerous tissues was an independent prognostic factor for both recurrence-free and overall survival in the 103 tumor specimens surgically resected from patients with PDAC. We established KDM6A knocked out cells by using the CRISPR/Cas9 system and KDM6A-expressed cells by doxycycline-inducible system from each two human PDAC cell lines, respectively. KDM6A knockout enhanced aggressive traits of human PDAC cell lines, whereas KDM6A overexpression suppressed them. Microarray analysis revealed reduced expression of 22 genes including five well-known tumor suppressors, such as CDKN1A, and ChIP-PCR analysis displayed depleted enrichment of histone H3 lysine 27 acetylation (H3K27ac) at the promoter regions of the five candidates. The epigenetic alterations were induced by the impaired recruitment of histone acetyltransferase p300, which cooperatively interacted with KDM6A. Consistent with these results, the KDM6A knockout cells demonstrated higher vulnerability to histone deacetylase (HDAC) inhibitors through the reactivation of CDKN1A in vitro and in vivo than the KDM6A wild-type. In conclusion, KDM6A exhibited essential roles in human PDAC as a tumor suppressor and KDM6A deficiency could be a promising biomarker for unfavorable outcome in PDAC patients and a potential surrogate marker for response to HDAC inhibitors.

The TRPM1 Channel Is Required for Development of the Rod ON Bipolar Cell-AII Amacrine Cell Pathway in the Retinal Circuit.

Neurotransmission plays an essential role in neural circuit formation in the central nervous system (CNS). Although neurotransmission has been recently clarified as a key modulator of retinal circuit development, the roles of individual synaptic transmissions are not yet fully understood. In the current study, we investigated the role of neurotransmission from photoreceptor cells to ON bipolar cells in development using mutant mouse lines of both sexes in which this transmission is abrogated. We found that deletion of the ON bipolar cation channel TRPM1 results in the abnormal contraction of rod bipolar terminals and a decreased number of their synaptic connections with amacrine cells. In contrast, these histological alterations were not caused by a disruption of total glutamate transmission due to loss of the ON bipolar glutamate receptor mGluR6 or the photoreceptor glutamate transporter VGluT1. In addition, TRPM1 deficiency led to the reduction of total dendritic length, branch numbers, and cell body size in AII amacrine cells. Activated Goα, known to close the TRPM1 channel, interacted with TRPM1 and induced the contraction of rod bipolar terminals. Furthermore, overexpression of Channelrhodopsin-2 partially rescued rod bipolar cell development in the TRPM1-/- retina, whereas the rescue effect by a constitutively closed form of TRPM1 was lower than that by the native form. Our results suggest that TRPM1 channel opening is essential for rod bipolar pathway establishment in development.SIGNIFICANCE STATEMENT Neurotransmission has been recognized recently as a key modulator of retinal circuit development in the CNS. However, the roles of individual synaptic transmissions are not yet fully understood. In the current study, we focused on neurotransmission between rod photoreceptor cells and rod bipolar cells in the retina. We used genetically modified mouse models which abrogate each step of neurotransmission: presynaptic glutamate release, postsynaptic glutamate reception, or transduction channel function. We found that the TRPM1 transduction channel is required for the development of rod bipolar cells and their synaptic formation with subsequent neurons, independently of glutamate transmission. This study advances our understanding of neurotransmission-mediated retinal circuit refinement.

Risk of hospitalization associated with anticholinergic medication for patients with dementia.

BACKGROUND: With the ageing of the general population, demand has grown for measures to prevent hospitalization for dementia, which can exacerbate problems associated with activities of daily living in elderly individuals. Anticholinergic medication has been shown to cause falls, delirium, and cognitive impairment in aged patients. However, the risk of hospitalization associated with the administration of anticholinergics is unclear. METHODS: We analyzed the records of 61 outpatients (26 men, 35 women; mean age: 78 ± 7 years; mean follow-up period: 420 days) diagnosed with dementia (Alzheimer's disease: n = 45; dementia with Lewy bodies: n = 3; undifferentiated n = 13) and prescribed anti-dementia drugs between May 2013 and December 2014. Medication history was noted, and the patients were divided into two groups according to the Anticholinergic Risk Scale: with risk (n = 13) and without risk (n = 48). Outcome was judged based on an end-point of hospitalization or death. Kaplan-Meier survival and Cox proportional hazard analyses were performed. RESULTS: Eight patients with anticholinergic risk and 12 without anticholinergic risk reached the end-point (P < 0.005). Analysis with a proportional hazard model showed that anticholinergic medication administration was related to a higher risk for reaching the end-point (crude hazard ratio: 3.62, 95% confidence interval: 1.45-9.04, P < 0.01; adjusted hazard ratio: 4.54, 95% confidence interval: 1.03-20.0, P < 0.05). In contrast, Mini-Mental State Examination score, Charlson Comorbidity Index, and the number of drugs were not major risk factors for hospitalization in patients with dementia. CONCLUSION: The Anticholinergic Risk Scale findings were shown to be a strong predictor of hospitalization for patients with dementia. We should evaluate the anticholinergic burden before initiating anti-dementia therapy.

Questionnaire survey of Japanese board-certified expert hepatobiliary and pancreatic surgeons and instructors on the surgical indications for hepatocellular carcinoma.

BACKGROUND: Recent advancements in systemic therapy for hepatocellular carcinoma (HCC) necessitate the establishment of resectability criteria for advanced HCC. METHODS: A questionnaire survey sought to clarify the perspectives of Japanese expert hepatobiliary surgeons regarding surgical indications for HCC. Thirty-one questions were used to determine when surgery is strongly recommended (resectable: R) or not recommended (unresectable: UR). RESULTS: A total of 351 responses were obtained. While 64.7% of the respondents considered solitary tumors as being R, irrespective of size, opinions diverged on the upper limit of the number of tumors/tumor size for R: (1) up to three nodules with no size limit (27.9%), (2) up to three nodules ≤5 cm in diameter each (21.4%) and (3) up to three nodules ≤3 cm in diameter each (19.4%). Vp1, Vp2, Vp3, and Vp4 were considered as being R by 90.9%, 70.7%, 39.0%, and 8.0% of respondents, respectively. Half of the respondents indicated they would consider resection even for cases with extrahepatic spread under limited conditions. CONCLUSIONS: The current views of Japanese expert surgeons on the resectability criteria for HCC were clarified for the first time. The findings could serve as a basis for preparing expert consensus statements on the resectability criteria for HCC.

[A case of scirrhous stomach cancer with follicular lymphoma of the duodenum].

The patient was a 73-year-old woman with hematemesis, who was brought to our hospital by an ambulance. Emergency upper gastrointestinal endoscopy was performed, and a thickened wall and multiple ulcers were noted in the middle- lower region of the stomach body. The biopsy revealed gastric cancer (por), and the macroscopic depth of invasion was up to the subserosal layer. Multiple white granular protruding lesions were observed in the duodenal bulb and were diagnosed as follicular lymphoma by biopsy. As follicular lymphoma generally takes a long time to progress in many cases, the vital prognosis would be determined by the gastric cancer. Thus, total gastrectomy was performed for gastric cancer. For reconstruction, the double-tract method was used. Duodenal follicular lymphoma was continuously monitored by upper gastrointestinal endoscopy. Here, we describe the case of a patient with a complication of follicular lymphoma arising from duodenal and gastric cancer, which is very rare, and report this case along with a literature review.

[A case of intussusception caused by low-grade appendiceal mucinous neoplasm with high serum levels of carcinoembryonic antigen resected by laparoscopy-assisted colectomy].

The patient was a 43-year-old woman who visited our hospital with a primary complaint of intermittent abdominal pain. Upper gastrointestinal endoscopy revealed mild gastritis. The patient was treated with oral drugs, and the course was followed. Subsequently, the abdominal pain aggravated, and computed tomography (CT) was performed, in which right colic intussusception with a 4 cm cystic mass in the advanced portion was noted. Reduction by enema was attempted on the same day; however, a residual tumorous lesion was present in the ileocecal region. The patient was diagnosed with a cecal submucosal tumor with intussusception, and therefore, laparoscopic surgery was performed. Intussusception of the entire appendix in the ascending colon was noted, for which laparoscopic ileocecal resection was performed. In the excised specimen, a cystic lesion comprising the appendix filled with mucus was present. The postoperative recovery was favorable, and the patient was discharged on the seventh postoperative day. The lesion was histopathologically diagnosed as low-grade appendiceal mucinous neoplasm.

[A case of locally advanced colorectal cancer with abscess responding to 5-fluorouracil, leucovorin, and oxaliplatin plus bevacizumab].

We encountered a case of colorectal cancer with pelvic abscess treated with radical surgery following colostomy and chemotherapy. The patient was a man in his 60s with advanced rectal cancer. The tumor had expanded locally and formed an abscess. We evaluated the primary lesion as unresectable, and performed chemotherapy with 5-fluorouracil, Leucovorin, and oxaliplatin( mFOLFOX) plus bevacizumab after colostomy. After 13 courses of chemotherapy, the tumor shrank remarkably. We performed a low anterior resection followed by adjuvant chemotherapy with capecitabine. The patient has had no recurrence for 18 months after surgery.

Epitranscriptome Mapping of N6-Methyladenosine Using m6A Immunoprecipitation with High Throughput Sequencing in Skeletal Muscle Stem Cells.

N6-Methyladenosine (m6A), one of the most abundant chemical modifications in mRNA (epitranscriptome), contributes to the regulation of biological processes by iterating gene expression post-transcriptionally. A number of publications on m6A modification have escalated in the recent past, due to the advancements in profiling m6A along the transcriptome using different approaches. The vast majority of studies primarily focused on m6A modification on cell lines but not primary cells. We present in this chapter a protocol for m6A immunoprecipitation with high throughput sequencing (MeRIP-Seq) that profiles m6A on mRNA with merely 100 µg total RNA worth of muscle stem cells as starting material. With this MeRIP-Seq, we observed epitranscriptome landscape in muscle stem cells.

Vasculitis, CA19-9, and Perineural Invasion Differentially Predict Response and Surgical Outcome in Pancreatic Ductal Adenocarcinoma.

PURPOSE: Curative intent treatment of pancreatic adenocarcinoma (PDAC) relies on surgical resection. Modern treatment protocols focus on optimizing neoadjuvant therapy to increase resectability and improve oncologic outcomes. To elucidate differences in outcomes, we investigated the relationship between neoadjuvant chemotherapy (NAC), either with or without stereotactic body radiation therapy (SBRT), and vascular inflammation, surgical outcomes, and the resultant transcriptomic changes. METHODS AND MATERIALS: Clinical data were collected from patients with borderline resectable PDAC (clinical T3-T4N0-1) who underwent NAC or NAC-SBRT followed by curative intent resection between 2014 and 2019. Vascular structures on surgical specimens were histologically evaluated for vasculitis. RNA sequencing was used to evaluate differential gene expression and to generate enrichment maps. Multivariate analysis was used to analyze the relationship between patient characteristics and oncological outcome. RESULTS: In total, 46 patients met inclusion criteria (n = 12 NAC, n = 34 NAC-SBRT) with a median follow-up of 20.1 months. All patients underwent curative resection, with 91.3% achieving R0. There was no significant difference in patterns of failure, overall survival, or progression-free survival between NAC and NAC-SBRT groups. Patients with vasculitis had a lower median overall survival compared with those without (14.5 vs 28.3 months; hazard ratio, 12.96; 95% confidence interval, 3.55-47.28; P < .001). There was no significant correlation between inflammation and surgical complications or pathologic response. Neoadjuvant therapy did not have a significant effect on development of vasculitis (odds radio, 1.64 for NAC-SBRT; 95% confidence interval, 0.40-8.43; P = .52). Predictors of poor survival included perineural invasion and high baseline carbohydrate antigen 19-9 (CA19-9) (>191 U/mL). Patients with robust CA19-9 (>20% decrease) responses to neoadjuvant therapy had enrichment in immune response, chemotaxis, and cytotoxic T-cell and natural killer-cell proliferation. CONCLUSIONS: Vasculitis predicts for poor survival outcomes in patients with PDAC; NAC-SBRT did not increase the rate of vasculitis compared with NAC. Perineural invasion and CA19-9 remain strong prognosticators. Understanding and optimizing immune interactions remain a crucial hurdle in achieving response in pancreatic cancer.

Loss of SFXN1 mitigates lipotoxicity and predicts poor outcome in non-viral hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) imposes a huge global burden, arising from various etiological factors such as hepatitis virus infection and metabolic syndrome. While prophylactic vaccination and antiviral treatment have decreased the incidence of viral HCC, the growing prevalence of metabolic syndrome has led to an increase in non-viral HCC. To identify genes downregulated and specifically associated with unfavorable outcome in non-viral HCC cases, screening analysis was conducted using publically available transcriptome data. Among top 500 genes meeting the criteria, which were involved in lipid metabolism and mitochondrial function, a serine transporter located on inner mitochondrial membrane SFXN1 was highlighted. SFXN1 protein expression was significantly reduced in 33 of 105 HCC tissue samples, and correlated to recurrence-free and overall survival only in non-viral HCC. Human HCC cells with SFXN1 knockout (KO) displayed higher cell viability, lower fat intake and diminished reactive oxygen species (ROS) production in response to palmitate administration. In a subcutaneous transplantation mouse model, high-fat diet feeding attenuated tumorigenic potential in the control cells, but not in the SFXN1-KO cells. In summary, loss of SFXN1 expression suppresses lipid accumulation and ROS generation, preventing toxic effects from fat overload in non-viral HCC, and predicts clinical outcome of non-viral HCC patients.

MGMT is frequently inactivated in pancreatic NET-G2 and is associated with the therapeutic activity of STZ-based regimens.

O6-methylguanine-DNA methyltransferase (MGMT) has been linked with alkylating agent resistance and tumor growth suppression. However, its role remains undetermined in pancreatic neuroendocrine tumors (Pan-NET). The MGMT expression was examined by immunohistochemistry in 142 patients to evaluate MGMT immunoreactivity and clinicopathological factors. We analyzed the relationship between MGMT expression and treatment efficacy in 19 patients who received STZ-based regimens. In 142 Pan-NET, 97 cases (68.3%) were judged as MGMT-positive and 45 cases (31.6%) as negative. MGMT negativity was significantly more common in NET-G2 (62.5%) than in NET-G1 (11.2%, p < 0.001). MGMT-negative cases were associated significantly with larger tumor size (p < 0.01), higher Ki-67 index (p < 0.01), higher mitotic index (p < 0.05), and more frequent liver metastasis (p < 0.05). Of the 19 cases treated with STZ, 6 cases were determined as SD and 4 cases as PD in MGMT-positive patients (N = 10), while 5 cases were determined as PR and 4 cases as SD in MGMT-negative patients (N = 9). Progression-free survival in MGMT-negative cases was significantly better than in MGMT-positive cases (p < 0.05). MGMT expression was lower in NET-G2 than in NET-G1, and STZ-based regimens improved the therapeutic outcomes of MGMT-negative Pan-NET. These findings indicate that NET-G2 may represent a better therapeutic target for STZ treatment.

RRM1 is mediated by histone acetylation through gemcitabine resistance and contributes to invasiveness and ECM remodeling in pancreatic cancer.

The invasiveness of pancreatic cancer and its resistance to anticancer drugs define its malignant potential, and are considered to affect the peritumoral microenvironment. Cancer cells with resistance to gemcitabine exposed to external signals induced by anticancer drugs may enhance their malignant transformation. Ribonucleotide reductase large subunit M1 (RRM1), an enzyme in the DNA synthesis pathway, is upregulated during gemcitabine resistance, and its expression is associated with worse prognosis for pancreatic cancer. However, the biological function of RRM1 is unclear. In the present study, it was demonstrated that histone acetylation is involved in the regulatory mechanism related to the acquisition of gemcitabine resistance and subsequent RRM1 upregulation. The current in vitro study indicated that RRM1 expression is critical for the migratory and invasive potential of pancreatic cancer cells. Furthermore, a comprehensive RNA sequencing analysis showed that activated RRM1 induced marked changes in the expression levels of extracellular matrix­related genes, including N­cadherin, tenascin­C and COL11A. RRM1 activation also promoted extracellular matrix remodeling and mesenchymal features, which enhanced the migratory invasiveness and malignant potential of pancreatic cancer cells. The present results demonstrated that RRM1 has a critical role in the biological gene program that regulates the extracellular matrix, which promotes the aggressive malignant phenotype of pancreatic cancer.