Intratumoural expression of deoxycytidylate deaminase or ribonuceotide reductase subunit M1 expression are not related to survival in patients with resected pancreatic cancer given adjuvant chemotherapy

Prognostic value of RRM1 and its effect on chemoresistance in pancreatic cancer

PURPOSE

Pancreatic cancer (PC) remains a lethal disease, and gemcitabine resistance is prevalent. However, the biomarkers suggestive of gemcitabine resistance remain unclear.

METHODS

Bioinformatic tools identified ribonucleotide reductase catalytic subunit M1 (RRM1) in gemcitabine-related datasets. A cox regression model revealed the predictive value of RRM1 with clinical features. An external clinical cohort confirmed the prognostic value of RRM1. RRM1 expression was validated in gemcitabine-resistant cells in vitro and in orthotopic PC model. CCK8, flow cytometry, transwell migration, and invasion assays were used to explore the effect of RRM1 on gemcitabine-resistant cells. The CIBERSORT algorithm investigated the impact of RRM1 on immune infiltration.

RESULTS

The constructed nomogram based on RRM1 effectively predicted prognosis and was further validated. Moreover, patients with higher RRM1 had shorter overall survival. RRM1 expression was significantly higher in PC tissue and gemcitabine-resistant cells in vitro and in vivo. RRM1 knockdown reversed gemcitabine resistance, inhibited migration and invasion. The infiltration levels of CD4 + T cells, CD8 + T cells, neutrophils, and plasma cells correlated markedly with RRM1 expression, and communication between tumor and immune cells probably depends on NF-κB/mTOR signaling.

CONCLUSION

RRM1 may be a potential marker for prognosis and a target marker for gemcitabine resistance in PC.

Adult T-cell leukemia-lymphoma acquires resistance to DNA demethylating agents through dysregulation of enzymes involved in pyrimidine metabolism

Adult T-cell leukemia-lymphoma (ATL) is an aggressive neoplasm derived from T-cells transformed by human T-cell lymphotropic virus-1 (HTLV-1). Recently, we reported that regional DNA hypermethylation in HTLV-1-infected T-cells reflects the disease status of ATL and the anti-ATL effects of DNA demethylating agents, including azacitidine (AZA), decitabine (DAC) and a new DAC prodrug, OR-2100 (OR21), which we developed. Here, to better understand the mechanisms underlying drug resistance, we generated AZA-, DAC- and OR21-resistant (AZA-R, DAC-R and OR21-R, respectively) cells from the ATL cell line TL-Om1 and the HTLV-1-infected cell line MT-2 via long-term drug exposure. The efficacy of OR21 was almost the same as that of DAC, indicating that the pharmacodynamics of OR21 were due to release of DAC from OR21. Resistant cells did not show cellular responses observed in parental cells induced by treatment with drugs, including growth suppression, depletion of DNA methyltransferase DNMT1 and DNA hypomethylation. We also found that reduced expression of deoxycytidine kinase (DCK) correlated with lower susceptibility to DAC/OR21 and that reduced expression of uridine cytidine kinase2 (UCK2) correlated with reduced susceptibility to AZA. DCK and UCK2 catalyze phosphorylation of DAC and AZA, respectively; reconstitution of expression reversed the resistant phenotypes. A large homozygous deletion in DCK and a homozygous splice donor site mutation in UCK2 were identified in DAC-R TL-Om1 and AZA-R TL-Om1, respectively. Both genomic mutations might lead to loss of protein expression. Thus, inactivation of UCK2 and DCK might be a putative cause of phenotypes that are resistant to AZA and DAC/OR21, respectively.

Therapeutic resistance in pancreatic ductal adenocarcinoma: Current challenges and future opportunities

Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer-related deaths in the United States. Although chemotherapeutic regimens such as gemcitabine+ nab-paclitaxel and FOLFIRINOX (FOLinic acid, 5-Fluroruracil, IRINotecan, and Oxaliplatin) significantly improve patient survival, the prevalence of therapy resistance remains a major roadblock in the success of these agents. This review discusses the molecular mechanisms that play a crucial role in PDAC therapy resistance and how a better understanding of these mechanisms has shaped clinical trials for pancreatic cancer chemotherapy. Specifically, we have discussed the metabolic alterations and DNA repair mechanisms observed in PDAC and current approaches in targeting these mechanisms. Our discussion also includes the lessons learned following the failure of immunotherapy in PDAC and current approaches underway to improve tumor's immunological response.

Chemotherapy for pancreatic cancer

Chemotherapy is an important part of multimodality pancreatic cancer treatment. After curative resection, adjuvant chemotherapy can significantly improve disease free survival and overall survival. The current standard of care is six months adjuvant chemotherapy with modified folinic acid, 5-fluorouracil, irinotecan and oxaliplatin (mFOLFIRINOX) in patients fit enough for this protocol, otherwise six months of gemcitabine and capecitabine based on the European Study Group for Pancreatic Cancer (ESPAC)-4 study. In patients with metastatic disease, combination chemotherapy according to the FOLFIRINOX protocol or with gemcitabine plus nab-paclitaxel is an important improvement to gemcitabine monotherapy that was the standard for many years. Patients not fit for combination chemotherapy however may still benefit from gemcitabine. Patients with good performance status may benefit from second-line chemotherapy. Chemoradiation has long been used in locally advanced pancreatic cancer but is now tempered following the LAP07 study. This trial showed no difference in overall survival in those patients with stable disease after four months of gemcitabine (with or without erlotinib) randomized to either continuation of gemcitabine therapy or chemoradiation (54Gy with capecitabine). As an alternative to radiation, other forms local therapies including radiofrequency ablation, irreversible electroporation, high-intensity focused ultrasound, microwave ablation and local anti-KRAS therapy (using siG12D-LODER) are currently under investigation. Given the systemic nature of pancreas cancer from an early stage, the success of any local approach other than complete surgical resection (with adjuvant systemic therapy) is likely to be very limited. In patients with locally advanced, irresectable cancer, chemotherapy may offer the chance for secondary resection with a survival similar to patients with primary resectable disease. Downstaging regimens need to be evaluated in prospective randomized trials in order to make firm recommendations. Selection of patient groups for specific therapy including cytotoxics is becoming a reality using assays based on drug cellular transport and metabolism, and molecular signatures. Going forward, high throughput screening of different chemotherapy agents using molecular signatures based on patients' derived organoids holds considerable promise.

Cytosolic 5'-nucleotidase 1A is overexpressed in pancreatic cancer and mediates gemcitabine resistance by reducing intracellular gemcitabine metabolites

BACKGROUND

Cytosolic 5'-nucleotidase 1A (NT5C1A) dephosphorylates non-cyclic nucleoside monophosphates to produce nucleosides and inorganic phosphates. Here, we investigate NT5C1A expression in pancreatic ductal adenocarcinoma (PDAC) and its impact on gemcitabine metabolism and therapeutic efficacy.

METHODS

NT5C1A expression was determined by semiquantitative immunohistochemistry using tissue microarrays. Gemcitabine metabolites and response were assessed in several human and murine PDAC cell lines using crystal violet assays, Western blot, viability assays, and liquid chromatography tandem mass-spectrometry (LC-MS/MS).

FINDINGS

NT5C1A was strongly expressed in tumor cells of a large subgroup of resected PDAC patients in two independent patient cohorts (44-56% score 2 and 8-26% score 3, n = 414). In contrast, NT5C1A was expressed at very low levels in the tumor stroma, and neither stromal nor tumoral expression was a prognostic marker for postoperative survival. In vitro, NT5C1A overexpression increased gemcitabine resistance by reducing apoptosis levels and significantly decreased intracellular amounts of cytotoxic dFdCTP in +NT5C1A tumor cells. Co-culture experiments with conditioned media from +NT5C1A PSCs improved gemcitabine efficacy in tumor cells. In vivo, therapeutic efficacy of gemcitabine was significantly decreased and serum levels of the inactive gemcitabine metabolite dFdU significantly increased in mice bearing NT5C1A overexpressing tumors.

INTERPRETATION

NT5C1A is robustly expressed in tumor cells of resected PDAC patients. Moreover, NT5C1A mediates gemcitabine resistance by decreasing the amount of intracellular dFdCTP, leading to reduced tumor cell apoptosis and larger pancreatic tumors in mice. Further studies should clarify the role of NT5C1A as novel predictor for gemcitabine treatment response in patients with PDAC.

Biomarkers and pathways of chemoresistance and chemosensitivity for personalized treatment of pancreatic adenocarcinoma

Pancreatic carcinoma is usually diagnosed late when treatment options are limited and is considered a chemo-resistant malignancy. However, early stage, good performance status and specific patient subgroup are thought to have a more favorable prognosis. Search for novel molecular biomarkers, which could predict treatment resistance, represents a major opportunity, but also a challenge in further research. This review summarizes most aspects of individualized therapy of pancreatic cancer including promising biomarkers, BRCA-deficient pancreatic cancer and its etiology. It may be estimated that nearly a third of metastatic pancreatic ductal adenocarcinoma patients could benefit from treatment other than gold standard chemotherapy. Thus, other aspects of an individualized approach concerning the main factors for the choice of the best therapy for individual pancreatic cancer patient (surgery and chemotherapy), as well as the future directions (target therapy and immunotherapy), are also addressed.

[Personalized cancer medicine : Biomarkers for molecular therapy stratification in pancreatic carcinoma]

Ductal adenocarcinoma of the pancreas has a very poor prognosis and a rising incidence. Even after curative intent resection, which is possible in a minority of patients, most patients relapse, whereas the majority is diagnosed with inoperable or metastatic disease. That's why palliative systemic chemotherapy is the current therapeutic mainstay. Biomarker-based tumor characterization could identify potential therapy targets and enable a personalized cancer medicine. Although potentially targetable alterations occur at very low frequencies, the possible impact on patient outcome can be significant. This article summarizes some of the contributions to these aspects and gives an outlook on their clinical meaning.

Nucleobase and Nucleoside Analogues: Resistance and Re-Sensitisation at the Level of Pharmacokinetics, Pharmacodynamics and Metabolism

Antimetabolites, in particular nucleobase and nucleoside analogues, are cytotoxic drugs that, starting from the small field of paediatric oncology, in combination with other chemotherapeutics, have revolutionised clinical oncology and transformed cancer into a curable disease. However, even though combination chemotherapy, together with radiation, surgery and immunotherapy, can nowadays cure almost all types of cancer, we still fail to achieve this for a substantial proportion of patients. The understanding of differences in metabolism, pharmacokinetics, pharmacodynamics, and tumour biology between patients that can be cured and patients that cannot, builds the scientific basis for rational therapy improvements. Here, we summarise current knowledge of how tumour-specific and patient-specific factors can dictate resistance to nucleobase/nucleoside analogues, and which strategies of re-sensitisation exist. We revisit well-established hurdles to treatment efficacy, like the blood-brain barrier and reduced deoxycytidine kinase activity, but will also discuss the role of novel resistance factors, such as SAMHD1. A comprehensive appreciation of the complex mechanisms that underpin the failure of chemotherapy will hopefully inform future strategies of personalised medicine.