Determinants of resistance to 2',2'-difluorodeoxycytidine (gemcitabine)

Role of octamer transcription factor 4 in proliferation, migration, drug sensitivity, and stemness maintenance of pancreatic cancer cells

BACKGROUND

Pancreatic cancer (PC) is one of the most aggressive malignancies characterized by rapid progression and poor prognosis. The involvement of cancer stem cells (CSCs) and Octamer transcription factor 4 (OCT4) in PC pathobiology is being increasingly recognized.

AIM

To investigate the role of OCT4 in pancreatic CSCs and its effect on PC cell proliferation, migration, drug sensitivity, and stemness maintenance.

METHODS

We analyzed OCT4 and CD133 expression in PC tissues and cell lines. BxPC-3 cells were used to assess the effects of OCT4 modulation on cellular behavior. Proliferation, migration, and stemness of BxPC-3 cells were evaluated, and the PI3K/AKT/mTOR pathway was examined to gain mechanistic insights.

RESULTS

OCT4 and CD133 were significantly overexpressed in PC tissues. OCT4 modulation altered BxPC-3 cell proliferation, invasion, and stemness, with OCT4 overexpression (OV-OCT4) enhancing these properties and OCT4 interference decreasing them. OV-OCT4 activated the PI3K/AKT/mTOR pathway, which correlated with an increase in PC stem cells (PCSC).

CONCLUSION

OCT4 plays a crucial role in PCSCs by influencing the aggressiveness and drug resistance of PC cells, thus presenting itself as a potential therapeutic target.

Raman imaging for monitoring deuterated squalene-gemcitabine nanomedicines in single living breast cancer cells

We have investigated the impact of gemcitabine (Gem) and deuterated gemcitabine-squalene (GemSQ-d6) nanoparticles (NPs) on MCF7 and MDA-MB-231 breast cancer cell lines by Raman spectroscopy. Quantification of LDL expression levels in both cell lines revealed a four-fold increase in MDA-MB-231 cells compared to MCF7 cells. In in vitro antitumor assessments, Gem displayed 13.5 times more effectiveness than GemSQ NPs against MCF7 cells, whereas GemSQ NPs induced a 14-fold increase in cytotoxicity compared to Gem for MDA-MB-231 cells. Oil Red O staining revealed that the treatment with GemSQ-d6 NPs induced a higher accumulation of lipid droplets at the periphery of the nucleus in MDA-MB-231 cells compared to MCF7 cells. Raman spectroscopy was employed to assess the impact of these drugs (50 µM, 24 hrs) on these breast cancer cell lines. By using the silent region (2000-2400 cm-1), we demonstrated that the accumulation of the GemSQ-d6 bioconjugate was higher in the cytoplasm of MDA-MB-231 cells than in MCF7 cells. This difference in drug accumulation is likely correlated with their expression levels of low-density lipoprotein receptors (LDLR). However, no information was obtained on Gem in this spectral region. We identified Raman features of squalene (SQ) in 700-1800 cm-1 fingerprint region that allowed us to observe almost the same distribution of GemSQ as that observed in the silent region for both cell lines treated with GemSQ-d6 or SQ-d6. Subsequently, the effects of Gem and GemSQ-d6 on cellular components such as proteins, nucleic acids, and cytochrome C were monitored within the fingerprint spectral region. Our results revealed distinct features in the subcellular accumulation of these biomolecules in response to Gem and GemSQ treatments.

Different Cytotoxic Effects of Cisplatin on Pancreatic Ductal Adenocarcinoma Cell Lines

This study examined the response to cisplatin in BxPC-3, Mia-Paca-2, PANC-1, and YAPC pancreatic cancer lines with different genotypic and phenotypic characteristics, and the mechanisms associated with their resistance. BxPC-3 and MIA-PaCa-2 cell lines were the most sensitive to cisplatin, while YAPC and PANC-1 were more resistant. Consistently, in cisplatin-treated BxPC-3 cells, the cleavage patterns of pro-caspase-9, -7, -3, and PARP-1 demonstrated that they were more sensitive than YAPC cells. The autophagic pathway, promoting cisplatin resistance, was active in BxPC-3 cells, as demonstrated by the time-dependent conversion of LC3-I to LC3-II, whereas it was not activated in YAPC cells. In cisplatin-treated BxPC-3 cells, Bcl-2 decreased, while Beclin-1, Atg-3, and Atg-5 increased along with JNK1/2 phosphorylation. Basal levels of phosphorylated ERK1/2 in each cell line were positively correlated with cisplatin IC50 values, and cisplatin caused the activation of ERK1/2 in BxPC-3 and YAPC cells. Furthermore, ERK1/2 pharmacological inactivation increased cisplatin lethality in both BxPC-3 and YAPC cells, suggesting that p-ERK1/2 may be related to cisplatin resistance of PDAC cells. Different mechanisms and strategies are generally required to acquire drug resistance. Here, we partially explain the other response to cisplatin of BxPC-3 and YAPC cell lines by relating it to the role of ERK pathway.

Atypical phosphatase DUSP11 inhibition promotes nc886 expression and potentiates gemcitabine-mediated cell death through NF-kB modulation

Pancreatic ductal adenocarcinoma (PDAC) represents one of the deadliest cancers among all solid tumors. First-line treatment relies on gemcitabine (Gem) and despite treatment improvements, refractoriness remains a universal challenge. Attempts to decipher how feedback-loops control signaling pathways towards drug resistance have gained attention in recent years, particularly focused on the role of phosphatases. In this study, a CRISPR/Cas9-based phenotypic screen was performed to identify members from the dual-specificity phosphatases (DUSP) family potentially acting on Gem response in PDAC cells. The approach revealed the atypical RNA phosphatase DUSP11 as a potential target, whose inhibition creates vulnerability of PDAC cells to Gem. DUSP11 genetic inhibition impaired cell survival and promoted apoptosis, synergistically enhancing Gem cytotoxicity. In silico transcriptome analysis of RNA-seq data from PDAC human samples identified NF-ĸB signaling pathway highly correlated with DUSP11 upregulation. Consistently, Gem-induced NF-ĸB phosphorylation was blocked upon DUSP11 inhibition in vitro. Mechanistically, we found that DUSP11 directly impacts nc886 expression and modulates PKR-NF-ĸB signaling cascade after Gem exposure in PDAC cells resulting in resistance to Gem-induced cell death. In conclusion, this study provides new insights on DUSP11 role in RNA biology and Gem response in PDAC cells.

Nucleo(s)tide metabolism as basis for drug development; the Anne Simmonds award lecture

Aberrant metabolism of purines and pyrimidines led to development of drugs for treatment of various diseases, such as inflammatory, neurological, cardiovascular, viral infections and cancer. Purine and Pyrimidine Symposia are characterized by close interactions, leading to extensive cross-fertilization on methodology and translating not only from bench-to-bedside, but also between various disciplines such as medicinal chemistry, pharmacology, oncology, virology, rheumatology, biochemistry, pediatrics, cardiology, surgery and immunology. This background was fundamental in our studies on how to optimize application of existing drugs (5-fluorouracil [5FU], thiopurines, antifolates such as methotrexate) but also to support development of novel drugs such as gemcitabine, novel antifolates, S-1, TAS-102 and fluorocyclopentenylcytosine. Knowledge of their metabolism helped to design rational combinations such as of gemcitabine with cisplatin, one of the most widely used drug combinations for various cancers. The combination of 5FU with uridine, led to the development of triacetyluridine registered for emergency treatment of patients with lethal 5FU toxicity. Mechanisms of action were studied by careful analysis of their metabolism, using classical enzyme assays with radioactive precursors and HPLC analysis. Drug metabolism moved from manually operated HPLC systems with UV-detection for peak identification and paper rolls for quantification, to computer-operated HPLC with automatic multi-wavelength and fluorometric peak detection and more recently to ultrasensitive, highly specific mass-spectrometry-based systems. Some aspects, however, never changed; careful analysis of the results and being prepared for the unexpected. The latter actually led to the most interesting results. Investigation of (nucleoside/nucleotide) metabolism remains an exciting field of research.

Exploring the Molecular Therapeutic Mechanisms of Gemcitabine through Quantitative Proteomics

Gemcitabine (GEM) is widely employed in the treatment of various cancers, including pancreatic cancer. Despite their clinical success, challenges related to GEM resistance and toxicity persist. Therefore, a deeper understanding of its intracellular mechanisms and potential targets is urgently needed. In this study, through mass spectrometry analysis in data-dependent acquisition mode, we carried out quantitative proteomics (three independent replications) and thermal proteome profiling (TPP, two independent replications) on MIA PaCa-2 cells to explore the effects of GEM. Our proteomic analysis revealed that GEM led to the upregulation of the cell cycle and DNA replication proteins. Notably, we observed the upregulation of S-phase kinase-associated protein 2 (SKP2), a cell cycle and chemoresistance regulator. Combining SKP2 inhibition with GEM showed synergistic effects, suggesting SKP2 as a potential target for enhancing the GEM sensitivity. Through TPP, we pinpointed four potential GEM binding targets implicated in tumor development, including in breast and liver cancers, underscoring GEM's broad-spectrum antitumor capabilities. These findings provide valuable insights into GEM's molecular mechanisms and offer potential targets for improving treatment efficacy.

Evaluation of the combination of gemcitabine, carboplatin, and lactate dehydrogenase A inhibitor on malignant mesothelioma

OBJECTIVES

Lactate dehydrogenase A (LDH-A) catalyzes the last step of glycolysis: supplying cells rapidly but inefficiently with ATP. Many tumors, including malignant mesothelioma (MM), have a high expression of LDH-A, which is associated with cancer aggressiveness. We aimed to determine whether the efficacy of the gemcitabine/carboplatin (Gem + Carbo) combination, widely used to treat this disease, could be increased by inhibition of LDH-A (by NHI-2). To this aim, we analyzed the growth inhibition of pleural and peritoneal MM by multiple combinations.

METHODS

The 72 h sulforhodamine B assay (SRB) was used to test the cytotoxicity of the combination of gemcitabine (in the range 0.1 - 400 nM) and carboplatin (0.01 - 40 µM) with a fixed concentration of NHI-2 (at IC25). We used pleural (H2452) and primary peritoneal (STO, MESO-II) MM cell lines, cultured at normoxic conditions.

RESULTS

NHI-2 did not increase the cytotoxicity of the combination of 100 nM gemcitabine and 10 µM carboplatin in peritoneal MM cell lines. The cell growth inhibition was 10% smaller after the triple combination than the Gem + Carbo treatment.

CONCLUSIONS

Inhibition of LDH-A did not increase the efficacy of gemcitabine and carboplatin in MM under normoxic conditions.

Targeting Intracranial Tumours with a Combination of RNA and Chemotherapy

Glioblastoma multiforme (GBM) is a fast-growing and aggressive brain tumour, which remains largely resistant to treatment; the prognosis for patients is poor, with a median survival time of about 12-18 months, post diagnosis. In an effort to bring more efficacious treatments to patients, we targeted the down regulation of ITCH, an E3 ligase that is overexpressed in a variety of cancers, and which inhibits P73, a tumour suppressor gene. 6-O-glycolchitosan (GC) was used to deliver siRNA ITCH (GC60-siRNA-ITCH) and gemcitabine via the nose to brain route in CD-1 nude mice which had previously been implanted intracranially with U87-MG-luc2 cells. Prior to this in vivo study, an in vitro study established the synergistic effect of siRNA-ITCH in combination with a chemotherapy drug-gemcitabine. A downregulation of ITCH, an upregulation of p73 and enhanced apoptosis were observed in vitro in U87-MG cells, using qPCR, Western blot analysis, confocal laser scanning microscopy, flow cytometry and cytotoxicity assays. When GC60-siRNA-ITCH was combined with gemcitabine, there was a resultant decrease in cell proliferation in vitro. In CD1 mice, the administration of siRNA-ITCH (7 doses of 0.081 mg/kg) alone did not significantly affect animal survival (increasing mean survival from 29 to 33 days when compared to untreated animals), whereas intranasal gemcitabine had a significant effect on survival (increasing survival from 29 to 45 days when compared to untreated animals, p < 0.01). The most significant effect was seen with combination therapy (GC60-siRNA-ITCH plus gemcitabine), where survival increased by 89%, increasing from 29 to 54 days (p < 0.01). Our data demonstrate that siRNA chemosensitises brain tumours to gemcitabine and that the nose-to-brain delivery route may be a viable route for the treatment of intracranial tumours.

Effects of nucleoside analogues, lipophilic prodrugs and elaidic acids on core signaling pathways in cancer cells

OBJECTIVES

Nucleoside analogs such as gemcitabine (GEM; dFdC) and cytarabine (Ara-C) require nucleoside transporters to enter cells, and deficiency in equilibrative nucleoside transporter 1 (ENT1) can lead to resistance to these drugs. To facilitate transport-independent uptake, prodrugs with a fatty acid chain attached to the 5'-position of the ribose group of gemcitabine or cytarabine were developed (CP-4126 and CP-4055, respectively). As antimetabolites can activate cellular survival pathways, we investigated whether the prodrugs or their side-chains had similar or decreased effects.

METHODS

Two cell lines A549 (non-small cell lung cancer) and WiDr (colon cancer cells) were exposed for 2-24hr to IC50 concentrations of GEM, Ara-C, CP-4126, CP4055 and elaidic acid (EA) concentrations corresponding to the CP-4126 and CP-4055 IC50. Cells were harvested and analyzed for proteins in cell survival pathways (p-AKT/AKT, p-ERK/ERK, p-P38/P38, GSK-3β/pGSK-3β) by using Western Blotting.

RESULTS

All drugs and their derivatives showed time- and cell-line-dependent effects. In A549 cells, GEM, CP-4126 and EA-4126 decreased the p-AKT/AKT ratio at 2 and 24 hr. For the p-ERK/ERK ratio, GEM, EA-4126, Ara-C, CP-4045 and EA-4055 exposure led to an increase after 6 hr in A549 cells. Interestingly, Ara-C, CP-4055 and EA-4055 decreased p-ERK/ERK ratio in WiDr cells after 4 hr. In A549 cells, the p-GSK-3β/GSK-3β ratio decreased after exposure to Ara-C and CP-4055 but in WiDr cells increased after 24 hr. In A549 cells treatment with Ara-C, CP-4055 and EA-4126 decreased the p-P38/P38 after 6 hr.

CONCLUSIONS

The findings suggest that both parent drugs, prodrugs, and the EA chain influence cell survival and signaling pathways.

Enhancing pancreatic ductal adenocarcinoma (PDAC) therapy with targeted carbon nano-onion (CNO)-mediated delivery of gemcitabine (GEM)-derived prodrugs

Nanotechnology's potential in revolutionising cancer treatments is evident in targeted drug delivery systems (DDSs) engineered to optimise therapeutic efficacy and minimise toxicity. This study examines a novel nanocarrier constructed with carbon nano-onions (CNOs), engineered and evaluated for its ability to selectively target cancer cells overexpressing the hyaluronic acid receptor; CD44. Our results highlighted that the CNO-based nanocarrier coupled with hyaluronic acid as the targeting agent demonstrated effective uptake by CD44+ PANC-1 and MIA PaCa-2 cells, while avoiding CD44- Capan-1 cells. The CNO-based nanocarrier also exhibited excellent biocompatibility in all tested pancreatic ductal adenocarcinoma (PDAC) cells, as well as healthy cells. Notably, the CNO-based nanocarrier was successfully loaded with chemotherapeutic 4-(N)-acyl- sidechain-containing prodrugs derived from gemcitabine (GEM). These prodrugs alone exhibited remarkable efficacy in killing PDAC cells which are known to be GEM resistant, and their efficacy was amplified when combined with the CNO-based nanocarrier, particularly in targeting GEM-resistant CD44+ PDAC cells. These findings demonstrate the potential of CNOs as promising scaffolds in advancing targeted DDSs, signifying the translational potential of carbon nanoparticles for cancer therapy.

Cytosolic 5'-Nucleotidase III and Nucleoside Triphosphate Diphosphohydrolase 1 Dephosphorylate the Pharmacologically Active Metabolites of Gemcitabine and Emtricitabine

Gemcitabine (dFdC) and emtricitabine (FTC) are first-line drugs that are used for the treatment of pancreatic cancer and human immunodeficiency virus, respectively. The above drugs must undergo sequential phosphorylation to become pharmacologically active. Interindividual variability associated with the responses of the above drugs has been reported. The molecular mechanisms underlying the observed variability are yet to be elucidated. Although this could be multifactorial, nucleotidases may be involved in the dephosphorylation of drug metabolites due to their structural similarity to endogenous nucleosides. With these in mind, we performed in vitro assays using recombinant nucleotidases to assess their enzymatic activities toward the metabolites of dFdC and FTC. From the above in vitro experiments, we noticed the dephosphorylation of dFdC-monophosphate in the presence of two 5'-nucleotidases (5'-NTs), cytosolic 5'-nucleotidase IA (NT5C1A) and cytosolic 5'-nucleotidase III (NT5C3), individually. Interestingly, FTC monophosphate was dephosphorylated only in the presence of NT5C3 enzyme. Additionally, nucleoside triphosphate diphosphohydrolase 1 (NTPDase 1) exhibited enzymatic activity toward both triphosphate metabolites of dFdC and FTC. Enzyme kinetic analysis further revealed Michaelis-Menten kinetics for both NT5C3-mediated dephosphorylation of monophosphate metabolites, as well as NTPDase 1-mediated dephosphorylation of triphosphate metabolites. Immunoblotting results confirmed the presence of NT5C3 and NTPDase 1 in both pancreatic and colorectal tissue that are target sites for dFdC and FTC treatment, respectively. Furthermore, sex-specific expression patterns of NT5C3 and NTPDase 1 were determined using mass spectrometry-based proteomics approach. Based on the above results, NT5C3 and NTPDase 1 may function in the control of the levels of dFdC and FTC metabolites. SIGNIFICANCE STATEMENT: Emtricitabine and gemcitabine are commonly used drugs for the treatment of human immunodeficiency virus and pancreatic cancer. To become pharmacologically active, both the above drugs must be phosphorylated. The variability in the responses of the above drugs can lead to poor clinical outcomes. Although the sources of drug metabolite concentration variability are multifactorial, it is vital to understand the role of nucleotidases in the tissue disposition of the above drug metabolites due to their structural similarities to endogenous nucleosides.

lncRNA CYTOR promotes lung adenocarcinoma gemcitabine resistance and epithelial-mesenchymal transition by sponging miR-125a-5p and upregulating ANLN and RRM2

Lung adenocarcinoma (LUAD) is one of the most aggressive types of lung cancer. The prognosis of LUAD patients remains poor, and the overall efficacy of gemcitabine-based chemotherapy is still unsatisfactory. Long noncoding RNAs (lncRNAs) play important roles in several cancer types by interacting with multiple proteins, RNA, and DNA. However, the relationship between lncRNA dysregulation and gemcitabine resistance in LUAD has not been fully elucidated. In this study, lncRNA CYTOR expression and its association with the prognosis of LUAD patients are assessed by quantitative RT-PCR and Kaplan-Meier survival analysis. In vitro and in vivo functional studies are conducted to evaluate the biological functions of CYTOR in LUAD. The underlying mechanism regarding the tumor-promoting effects of CYTOR is explored using RNA immunoprecipitation, biotin-labelled RNA pulldown, luciferase reporter assays, and western blot analysis. We identify that CYTOR is an oncogenic lncRNA and is apparently upregulated in LUAD by analysing TCGA-LUAD data. High CYTOR expression is a poor prognostic factor for LUAD. Functional studies reveal that CYTOR confers LUAD cells with stronger resistance to gemcitabine treatment and upregulates the expression levels of epithelial-mesenchymal transition (EMT)-related proteins. Mechanically, CYTOR acts as a competitive endogenous RNA (ceRNA) to absorb miR-125a-5p, weakens the antitumor function of miR-125a-5p, and ultimately upregulates ANLN and RRM2 expressions. Taken together, this study explains the mechanism of lncRNA in the gemcitabine resistance of LUAD and formulates a theoretical framework for the in depth study of LUAD.

Long non-coding RNAs and tyrosine kinase-mediated drug resistance in pancreatic cancer

Pancreatic cancer (PC) is one of the most malignant tumors with a dismal survival rate, this is primarily due to inevitable chemoresistance. Dysfunctional tyrosine kinases (TKs) and long non-coding RNAs (lncRNAs) affect the drug resistance and prognosis of PC. Here, we summarize the mechanisms by which TKs or lncRNAs mediate drug resistance and other malignant phenotypes. We also discuss that lncRNAs play oncogenic or tumor suppressor roles and different mechanisms including lncRNA-proteins/microRNAs to mediate drug resistance. Furthermore, we highlight that lncRNAs serve as upstream regulators of TKs mediating drug resistance. Finally, we display the clinical significance of TKs (AXL, EGFR, IGF1R, and MET), clinical trials, and lncRNAs (LINC00460, PVT1, HIF1A-AS1). In the future, TKs and lncRNAs may become diagnostic and prognostic biomarkers or drug targets to overcome the drug resistance of PC.

Exploring the therapeutic potential of focal adhesion kinase inhibition in overcoming chemoresistance in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is among the leading causes of cancer-related deaths worldwide. Focal adhesion kinase (FAK) is a nonreceptor tyrosine kinase often overexpressed in PDAC. FAK has been linked to cell migration, survival, proliferation, angiogenesis and adhesion. This review first highlights the chemoresistant nature of PDAC. Second, the role of FAK in PDAC cancer progression and resistance is carefully described. Additionally, it discusses recent developments of FAK inhibitors as valuable drugs in the treatment of PDAC, with a focus on diamine-substituted-2,4-pyrimidine-based compounds, which represent the most potent class of FAK inhibitors in clinical trials for the treatment of PDAC disease. To conclude, relevant computational studies performed on FAK inhibitors are reported to highlight the key structural features required for interaction with the protein, with the aim of optimizing this novel targeted therapy.

Glycogen synthase kinase 3β: the nexus of chemoresistance, invasive capacity, and cancer stemness in pancreatic cancer

The treatment of pancreatic cancer remains a significant clinical challenge due to the limited number of patients eligible for curative (R0) surgery, failures in the clinical development of targeted and immune therapies, and the pervasive acquisition of chemotherapeutic resistance. Refractory pancreatic cancer is typified by high invasiveness and resistance to therapy, with both attributes related to tumor cell stemness. These malignant characteristics mutually enhance each other, leading to rapid cancer progression. Over the past two decades, numerous studies have produced evidence of the pivotal role of glycogen synthase kinase (GSK)3β in the progression of over 25 different cancer types, including pancreatic cancer. In this review, we synthesize the current knowledge on the pathological roles of aberrant GSK3β in supporting tumor cell proliferation and invasion, as well as its contribution to gemcitabine resistance in pancreatic cancer. Importantly, we discuss the central role of GSK3β as a molecular hub that mechanistically connects chemoresistance, tumor cell invasion, and stemness in pancreatic cancer. We also discuss the involvement of GSK3β in the formation of desmoplastic tumor stroma and in promoting anti-cancer immune evasion, both of which constitute major obstacles to successful cancer treatment. Overall, GSK3β has characteristics of a promising therapeutic target to overcome chemoresistance in pancreatic cancer.

A new technique for the analysis of metabolic pathways of cytidine analogues and cytidine deaminase activities in cells

Deoxycytidine analogues (dCas) are widely used for the treatment of malignant diseases. They are commonly inactivated by cytidine deaminase (CDD), or by deoxycytidine monophosphate deaminase (dCMP deaminase). Additional metabolic pathways, such as phosphorylation, can substantially contribute to their (in)activation. Here, a new technique for the analysis of these pathways in cells is described. It is based on the use of 5-ethynyl 2'-deoxycytidine (EdC) and its conversion to 5-ethynyl 2'-deoxyuridine (EdU). Its use was tested for the estimation of the role of CDD and dCMP deaminase in five cancer and four non-cancer cell lines. The technique provides the possibility to address the aggregated impact of cytidine transporters, CDD, dCMP deaminase, and deoxycytidine kinase on EdC metabolism. Using this technique, we developed a quick and cheap method for the identification of cell lines exhibiting a lack of CDD activity. The data showed that in contrast to the cancer cells, all the non-cancer cells used in the study exhibited low, if any, CDD content and their cytidine deaminase activity can be exclusively attributed to dCMP deaminase. The technique also confirmed the importance of deoxycytidine kinase for dCas metabolism and indicated that dCMP deaminase can be fundamental in dCas deamination as well as CDD. Moreover, the described technique provides the possibility to perform the simultaneous testing of cytotoxicity and DNA replication activity.

Liposomal nanocarriers containing siRNA as small molecule-based drugs to overcome cancer drug resistance

This review discusses the application of nanoliposomes containing siRNA/drug to overcome multidrug resistance for all types of cancer treatments. As drug resistance-associated factors are overexpressed in many cancer cell types, pumping chemotherapy drugs out of the cytoplasm leads to an inadequate therapeutic response. The siRNA/drug-loaded nanoliposomes are a promising approach to treating multidrug-resistant cancer, as they can effectively transmit a small-molecule drug into the target cytoplasm, ensuring that the drug binds efficiently. Moreover, nanoliposome-based therapeutics with advances in nanotechnology can effectively deliver siRNA to cancer cells. Overall, nanoliposomes have the potential to effectively deliver siRNA and small-molecule drugs in a targeted manner and are thus a promising tool for the treatment of cancer and other diseases.

Polarization of Cancer-Associated Macrophages Maneuver Neoplastic Attributes of Pancreatic Ductal Adenocarcinoma

Mounting evidence links the phenomenon of enhanced recruitment of tumor-associated macrophages towards cancer bulks to neoplastic growth, invasion, metastasis, immune escape, matrix remodeling, and therapeutic resistance. In the context of cancer progression, naïve macrophages are polarized into M1 or M2 subtypes according to their differentiation status, gene signatures, and functional roles. While the former render proinflammatory and anticancer effects, the latter subpopulation elicits an opposite impact on pancreatic ductal adenocarcinoma. M2 macrophages have gained increasing attention as they are largely responsible for molding an immune-suppressive landscape. Through positive feedback circuits involving a paracrine manner, M2 macrophages can be amplified by and synergized with neighboring neoplastic cells, fibroblasts, endothelial cells, and non-cell autonomous constituents in the microenvironmental niche to promote an advanced disease state. This review delineates the molecular cues expanding M2 populations that subsequently convey notorious clinical outcomes. Future therapeutic regimens shall comprise protocols attempting to abolish environmental niches favoring M2 polarization; weaken cancer growth typically assisted by M2; promote the recruitment of tumoricidal CD8⁺ T lymphocytes and dendritic cells; and boost susceptibility towards gemcitabine as well as other chemotherapeutic agents.

Visualization research on ENT1/NIS dual-function gene therapy to reverse drug resistance mediated by MUC1 in GEM-resistant pancreatic cancer

PURPOSE

To use bifunctional target genes to increase the intracellular transport of gemcitabine (GEM) to reverse chemotherapy resistance and to simultaneously use reporter gene imaging to localize therapeutic genes. The therapeutic effect was evaluated by [¹⁸F]FLT PET/CT to visualize the effect of gene therapy.

METHODS

A viral gene vector containing the pancreatic cancer-targeting promoter MUC1 for specific transcription of equilibrative nucleoside transporter 1 (ENT1) and NIS (nuclide transport channel) was employed. [¹²⁵I]NaI uptake tests and [¹³¹I]NaI SPECT imaging were performed to verify the function of NIS and the target function of MUC1. The correlation between [¹⁸F]FLT uptake and GEM resistance were assessed, and the influence ENT1 and thymidine kinase 1 (TK1) expression on [¹⁸F]FLT micro-PET/CT was measured, which provides a theoretical basis for the use of [¹⁸F]FLT micro-PET/CT to evaluate the efficacy of gene therapy.

RESULTS

First, functions of gene therapy were confirmed: ENT1 reversed the drug resistance of GEM-resistant pancreatic cancer cells by increasing GEM intracellular transport; MUC1 drove NIS target gene expression in pancreatic cancer; and therapeutic genes could be localized using [¹³¹I]NaI SPECT reporter gene imaging. Second, the [¹⁸F]FLT uptake ratio was affected by drug resistance and GEM treatment. The mechanism underlying this effect was related to ENT1 and TK1. Increased expression of ENT1 inhibited the expression of TK1 after GEM chemotherapy to reduce the uptake of [¹⁸F]FLT. Finally, micro-PET/CT indicated that the SUV_max of [¹⁸F]FLT could predict survival time. SUV_max exhibited an increasing trend in resistant pancreatic cancer but a trend of inhibition after upregulation of ENT1, which was more significant after GEM treatment.

CONCLUSIONS

Bifunctional targeted genes can localize therapeutic genes through reporter gene imaging, reverse the drug resistance of GEM-resistant pancreatic cancer and be visually evaluated through [¹⁸F]FLT micro-PET/CT.

Comparative Proteomic Analysis Identifies Key Metabolic Regulators of Gemcitabine Resistance in Pancreatic Cancer

Pancreatic adenocarcinoma (PDAC) is highly refractory to treatment. Standard-of-care gemcitabine (Gem) provides only modest survival benefits, and development of Gem resistance (GemR) compromises its efficacy. Highly GemR clones of Gem-sensitive MIAPaCa-2 cells were developed to investigate the molecular mechanisms of GemR and implemented global quantitative differential proteomics analysis with a comprehensive, reproducible ion-current-based MS1 workflow to quantify ∼6000 proteins in all samples. In GemR clone MIA-GR8, cellular metabolism, proliferation, migration, and 'drug response' mechanisms were the predominant biological processes altered, consistent with cell phenotypic alterations in cell cycle and motility. S100 calcium binding protein A4 was the most downregulated protein, as were proteins associated with glycolytic and oxidative energy production. Both responses would reduce tumor proliferation. Upregulation of mesenchymal markers was prominent, and cellular invasiveness increased. Key enzymes in Gem metabolism pathways were altered such that intracellular utilization of Gem would decrease. Ribonucleoside-diphosphate reductase large subunit was the most elevated Gem metabolizing protein, supporting its critical role in GemR. Lower Ribonucleoside-diphosphate reductase large subunit expression is associated with better clinical outcomes in PDAC, and its downregulation paralleled reduced MIAPaCa-2 proliferation and migration and increased Gem sensitivity. Temporal protein-level Gem responses of MIAPaCa-2 versus GemR cell lines (intrinsically GemR PANC-1 and acquired GemR MIA-GR8) implicate adaptive changes in cellular response systems for cell proliferation and drug transport and metabolism, which reduce cytotoxic Gem metabolites, in DNA repair, and additional responses, as key contributors to the complexity of GemR in PDAC. These findings additionally suggest targetable therapeutic vulnerabilities for GemR PDAC patients.

Role of drug catabolism, modulation of oncogenic signaling and tumor microenvironment in microbe-mediated pancreatic cancer chemoresistance

Pancreatic ductal adenocarcinoma (PDAC) has one of the highest incidence/death ratios among all neoplasms due to its late diagnosis and dominant chemoresistance. Most PDAC patients present with an advanced disease characterized by a multifactorial, inherent and acquired resistance to current anticancer treatments. This remarkable chemoresistance has been ascribed to several PDAC features including the genetic landscape, metabolic alterations, and a heterogeneous tumor microenvironment that is characterized by dense fibrosis, and a cellular contexture including functionally distinct subclasses of cancer-associated fibroblasts, immune suppressive cells, but also a number of bacteria, shaping a specific tumor microbiome microenvironment. Thus, recent studies prompted the emergence of a new research avenue, by describing the role of the microbiome in gemcitabine resistance, while next-generation-sequencing analyses identified a specific microbiome in different tumors, including PDAC. Functionally, the contribution of these microbes to PDAC chemoresistance is only beginning to be explored. Here we provide an overview of the studies demonstrating that bacteria have the capacity to metabolically transform and hence inactivate anticancer drugs, as exemplified by the inhibition of the efficacy of 10 out of 30 chemotherapeutics by Escherichia coli. Moreover, a number of bacteria modulate specific oncogenic pathways, such as Fusobacterium nucleatum, affecting autophagy and apoptosis induction by 5-fluorouracil and oxaliplatin. We hypothesize that improved understanding of how chemoresistance is driven by bacteria could enhance the efficacy of current treatments, and discuss the potential of microbiome modulation and targeted therapeutic approaches as well as the need for more reliable models and biomarkers to translate the findings of preclinical/translational research to the clinical setting, and ultimately overcome PDAC chemoresistance, hence improving clinical outcome.

Genome-Wide CRISPR Screening Identifies DCK and CCNL1 as Genes That Contribute to Gemcitabine Resistance in Pancreatic Cancer

Simple Summary

Pancreatic cancer is one of the most lethal cancers. Although complete surgical resection is the only curative treatment for pancreatic cancer, a late diagnosis is common and makes surgical treatment infeasible. Therefore, most patients receive chemotherapy to reduce the tumor burden. Gemcitabine has been the main chemotherapy for pancreatic cancer for over a decade; however, chemoresistance has emerged as a significant challenge to the efficacy of chemotherapy. In this study, we applied genome-wide CRISPR/Cas9 loss-of-function screening with gemcitabine treatment to identify DCK and CCNL1 as genes that contribute to gemcitabine resistance in pancreatic cancer and explored the mechanism of CCNL1-related gemcitabine resistance.

Abstract

Pancreatic cancer is one of the most lethal cancers. Due to the difficulty of early diagnosis, most patients are diagnosed with metastasis or advanced-stage cancer, limiting the possibility of surgical treatment. Therefore, chemotherapy is applied to improve patient outcomes, and gemcitabine has been the primary chemotherapy drug for pancreatic cancer for over a decade. However, drug resistance poses a significant challenge to the efficacy of chemotherapy. The CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9) gene-editing system is a powerful tool, and researchers have developed CRISPR/Cas9 library screening as a means to identify the genes associated with specific phenotype changes. We performed genome-wide CRISPR/Cas9 knockout screening in the mouse pancreatic cancer cell line TB32047 with gemcitabine treatment and identified deoxycytidine kinase (DCK) and cyclin L1 (CCNL1) as the top hits. We knocked out DCK and CCNL1 in the TB32047 and PANC1 cell lines and confirmed that the loss of DCK or CCNL1 enhanced gemcitabine resistance in pancreatic cells. Many researchers have addressed the mechanism of DCK-related gemcitabine resistance; however, no study has focused on CCNL1 and gemcitabine resistance. Therefore, we explored the mechanism of CCNL1-related gemcitabine resistance and found that the loss of CCNL1 activates the ERK/AKT/STAT3 survival pathway, causing cell resistance to gemcitabine treatment.

E2F2 enhances the chemoresistance of pancreatic cancer to gemcitabine by regulating the cell cycle and upregulating the expression of RRM2

Both pro-oncogenic and anti-oncogenic effects of E2F2 have been revealed in different malignancies. However, the precise role of E2F2 in pancreatic cancer, in particular in relation to therapeutic intervention with gemcitabine, remains unclear. In this study, the effect of E2F2 on the proliferation and cell cycle modulation of pancreatic cancer cells, and whether E2F2 plays a role in the treatment of pancreatic cancer cells by gemcitabine, were investigated. The expression of E2F2 in pancreatic cancer was assessed by various methods including bioinformatics prediction, Western blotting, and real-time PCR. The effect of E2F2 on the proliferation and cell cycling of pancreatic cancer cells was analyzed by tissue culture and flow cytometry. In addition, the effect of E2F2 on the intervention of pancreatic cancer by gemcitabine was investigated using both in vitro and in vivo approaches. The expression of E2F2 was found to be significantly increased in pancreatic cancer tissues and cell lines. The pathogenic capacity of E2F2 lied in the fact that this transcription factor promoted the transformation of pancreatic cancer cell cycle from G1-phase to S-phase, thus enhancing the proliferation of pancreatic cancer cells. Furthermore, the expression of E2F2 was increased in pancreatic cancer cells in the presence of gemcitabine, and the augmented expression of E2F2 upregulated the gemcitabine resistance-related gene RRM2 and its downstream signaling molecule deoxycytidine kinase (DCK). The resistance of pancreatic cancer cells to gemcitabine was confirmed using both in vitro and in vivo models. In this study, E2F2 has been demonstrated for the first time to play a pro-oncogenic role in pancreatic cancer by promoting the transition of the cell cycle from G1-phase to S-phase and, therefore, enhancing the proliferation of pancreatic cancer cells. E2F2 has also been demonstrated to enhance the chemotherapy resistance of pancreatic cancer cells to gemcitabine by upregulating the expression of RRM2 and DCK that is downstream of RRM2.

Penetrating Micelle for Reversing Immunosuppression and Drug Resistance in Pancreatic Cancer Treatment

Pancreatic ductal adenocarcinoma (PDAC) is on of the most lethal malignant tumors with relatively poor prognosis, characterized with insufficient drug penetration, low immune response and obvious drug resistances. The therapeutic inefficiency is multifactorially related to its specific tumor microenvironment (TME), which is representatively featured as rich stroma and immunosuppression. In this work, a versatile drug delivery system is developed that can coencapsulate two prodrugs modified from gemcitabine (GEM) and a signal transducer and activator of transcription 3 (STAT3) inhibitor (HJC0152), and the gradient pH variation is further sensed in the TME of PDAC to achieve a higher penetration by reversing its surficial charges. The escorted prodrugs can release GEM intracellularly, and respond to the hypoxic condition to yield the parental STAT3 inhibitor HJC0152, respectively. By inhibiting STAT3, the tumor immunosuppression microenvironment can be re-educated through the reversion of M2-like tumor associated macrophages (M2-TAMs), recruitment of cytotoxic T lymphocytes and downregulation of regulatory T cells (Treg s). Furthermore, cytidine deaminase (CDA) and α-smooth muscle actin (α-SMA) expression can be downregulated, plus the lipid modification of GEM, the drug resistance of GEM can be greatly relieved. Based on the above design, a synergetic therapeutic efficacy in PDAC treatment can be achieved to provide more opportunity for clinical applications.

Targeting the complement system in pancreatic cancer drug resistance: a novel therapeutic approach

Pancreatic cancer is ranked as the fourth leading cause of cancer-related mortality and is predicted to become the second leading cause of cancer-related death by 2030. The cause of this high mortality rate is due to pancreatic ductal adenocarcinoma's rapid progression and metastasis, and development of drug resistance. Today, cancer immunotherapy is becoming a strong candidate to not only treat various cancers but also to combat against chemoresistance. Studies have suggested that complement system pathways play an important role in cancer progression and chemoresistance, especially in pancreatic cancer. A recent report also suggested that several signaling pathways play an important role in causing chemoresistance in pancreatic cancer, major ones including nuclear factor kappa B, signal transducer and activator of transcription 3, c-mesenchymal-epithelial transition factor, and phosphoinositide-3-kinase/protein kinase B. In addition, it has also been proven that the complement system has a very active role in establishing the tumor microenvironment, which would aid in promoting tumorigenesis, progression, metastasis, and recurrence. Interestingly, it has been shown that the downstream products of the complement system directly upregulate inflammatory mediators, which in turn activate these chemo-resistant pathways. Therefore, targeting complement pathways could be an innovative approach to combat against pancreatic cancer drugs resistance. In this review, we have discussed the role of complement system pathways in pancreatic cancer drug resistance and a special focus on the complement as a therapeutic target in pancreatic cancer.

Gemcitabine-Resistant Biomarkers in Bladder Cancer are Associated with Tumor-Immune Microenvironment

To identify key biomarkers in gemcitabine (GEM)-resistant bladder cancer (BCa) and investigate their associations with tumor-infiltrating immune cells in a tumor immune microenvironment, we performed the present study on the basis of large-scale sequencing data. Expression profiles from the Gene Expression Omnibus GSE77883 dataset and The Cancer Genome Atlas BLCA dataset were analyzed. Both BCa development and GEM-resistance were identified to be immune-related through evaluating tumor-infiltrating immune cells. Eighty-two DEGs were obtained to be related to GEM-resistance. Functional enrichment analysis demonstrated they were related to regulation of immune cells proliferation. Protein-protein interaction network selected six key genes (CAV1, COL6A2, FABP4, FBLN1, PCOLCE, and CSPG4). Immunohistochemistry confirmed the down-regulation of the six key genes in BCa. Survival analyses revealed the six key genes were significantly associated with BCa overall survival. Correlation analyses revealed the six key genes had high infiltration of most immune cells. Gene set enrichment analysis further detected the key genes might regulate GEM-resistance through immune response and drug metabolism of cytochrome P450. Next, microRNA-gene regulatory network identified three key microRNAs (hsa-miR-124-3p, hsa-miR-26b-5p, and hsa-miR-192-5p) involved in GEM-resistant BCa. Connectivity Map analysis identified histone deacetylase inhibitors might circumvent GEM-resistance. In conclusion, CAV1, COL6A2, FABP4, FBLN1, PCOLCE, and CSPG4 were identified to be critical biomarkers through regulating the immune cell infiltration in an immune microenvironment of GEM-resistance and could act as promising treatment targets for GEM-resistant muscle-invasive BCa.

Histone acetyltransferase 1 promotes gemcitabine resistance by regulating the PVT1/EZH2 complex in pancreatic cancer

The poor prognosis of pancreatic cancer is primarily due to the development of resistance to therapies, including gemcitabine. The long noncoding RNA PVT1 (lncRNA PVT1) has been shown to interact with enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2), promoting gemcitabine resistance in pancreatic cancer. In this study, we found histone acetyltransferase 1 (HAT1) enhanced the tolerance of pancreatic cancer cells to gemcitabine and HAT1-mediated resistance mechanisms were regulated by PVT1 and EZH2. Our results showed that the aberrant HAT1 expression promoted gemcitabine resistance, while silencing HAT1 restored gemcitabine sensitivity. Moreover, HAT1 depletion caused a notable increase of gemcitabine sensitivity in gemcitabine-resistant pancreatic cancer cell lines. Further research found that HAT1 increased PVT1 expression to induce gemcitabine resistance, which enhanced the binding of bromodomain containing 4 (BRD4) to the PVT1 promoter, thereby promoting PVT1 transcription. Besides, HAT1 prevented EZH2 degradation by interfering with ubiquitin protein ligase E3 component n-recognin 4 (UBR4) binding to the N-terminal domain of EZH2, thus maintaining EZH2 protein stability to elevate the level of EZH2 protein, which also promoted HAT1-mediated gemcitabine resistance. These results suggested that HAT1 induced gemcitabine resistance of pancreatic cancer cells through regulating PVT1/EZH2 complex. Given this, Chitosan (CS)-tripolyphosphate (TPP)-siHAT1 nanoparticles were developed to block HAT1 expression and improve the antitumor effect of gemcitabine. The results showed that CS-TPP-siHAT1 nanoparticles augmented the antitumor effects of gemcitabine in vitro and in vivo. In conclusion, HAT1-targeted therapy can improve observably gemcitabine sensitivity of pancreatic cancer cells. HAT1 is a promising therapeutic target for pancreatic cancer.

The Use of Heptamethine Cyanine Dyes as Drug-Conjugate Systems in the Treatment of Primary and Metastatic Brain Tumors

Effective cancer therapeutics for brain tumors must be able to cross the blood-brain barrier (BBB) to reach the tumor in adequate quantities and overcome the resistance conferred by the local tumor microenvironment. Clinically approved chemotherapeutic agents have been investigated for brain neoplasms, but despite their effectiveness in peripheral cancers, failed to show therapeutic success in brain tumors. This is largely due to their poor bioavailability and specificity towards brain tumors. A targeted delivery system might improve the efficacy of the candidate compounds by increasing the retention time in the tumor tissue, and minimizing the numerous side effects associated with the non-specific distribution of the chemotherapy agent. Heptamethine cyanine dyes (HMCDs) are a class of near-infrared fluorescence (NIRF) compounds that have recently emerged as promising agents for drug delivery. Initially explored for their use in imaging and monitoring neoplasms, their tumor-targeting properties have recently been investigated for their use as drug carrier systems. This review will explore the recent developments in the tumour-targeting properties of a specific group of NIRF cyanine dyes and the preclinical evidence for their potential as drug-delivery systems in the treatment of primary and metastatic brain tumors.

Colossolactone-G synergizes the anticancer properties of 5-fluorouracil and gemcitabine against colorectal cancer cells

Several terpenoids were isolated from Ganoderma colossum with potential chemotherapeutic properties against different solid tumor cells. Herein, we further assessed the potential chemomodulatory effects of colossolactone-G to gemcitabine (GCB) and 5-fluorouracil (5-FU) against colorectal cancer cells. Colossolactone-G induced moderate cell killing effects against both HT-29 and HCT-116 cells, with IC₅₀'s of 90.5 ± 1.7 µM and 22.3 ± 3.9 µM, respectively. Equitoxic combination demonstrated a synergistic effect between colossolactone-G and GCB, or 5-FU with combination indices ranging from 0.22 to 0.67. Both GCB and 5-FU induced moderate cell cycle arrest at G₀/G₁-phase and S-phase. Despite colossolactone-G's lack of influence on cell cycle distribution, it significantly potentiated GCB- and 5-FU-induced cell cycle arrest. Similarly, colossolactone-G treatment alone did not induce pronounced apoptosis in both cell lines. However, 5-FU and GCB induced significant apoptosis which was further potentiated via combination with colossolactone-G. Furthermore, colossolactone-G significantly increased autophagic cell death response in both HCT-116 and HT-29 cells and potentiated 5-FU- and GCB-induced autophagic cell death. The influence of colossolactone-G alone or in combination with GCB or 5-FU on the apoptosis and autophagy were confirmed by qPCR analysis for the expression of several key apoptosis and autophagy genes such as, TRAIL, TP53INP1, BNIP3, hp62, ATG5, ATG7, Lamp2A and the golden standard for autophagy (LC3-II). In conclusion, a synergistic effect in terms of anticancer properties was observed when colossolactone-G was combined with 5-FU and GCB, where it influenced both apoptosis and autophagic cell death mechanisms.

Synthesis, Antitumor and Antiviral In Vitro Activities of New Benzotriazole-Dicarboxamide Derivatives

Cancer and viral infections continue to threaten humankind causing death worldwide. Hence, the discovery of new anticancer and antiviral agents still represents a major scientific goal. Heterocycles designed to mimic the chemical structure of natural pyrimidines and purines have been designed over the years, exerting their activity acting as false substrates on several different targets. We reported a series of bis-benzotriazole-dicarboxamide derivatives which inhibit viral helicase of poliovirus, and hence we planned structure modifications to obtain different series of new dicarboxamides. Here, the synthesis and characterization of 56 new compounds: 31 bis-benzotriazole dicarboxamides and 25 mono-substituted acidic derivatives are reported. The synthesized compounds were tested for their antiviral and antitumor activity. Mostly, compounds 4a, 4c and 4d showed antiviral activity against tested Picornaviruses, Coxsackievirus B5 and Poliovirus-1. Likewise, four derivatives (3b, 3d, 4d, 9b) showed notable antiproliferative activity inhibiting cell growth in two distinct antitumor screenings. Compound 3b was selected as the antitumor lead compound for the wide range of activity and the potency proved. The lead compound was proved to induce apoptosis in SK-MES1 tumor cells, in a dose-dependent manner.

KNSTRN promotes tumorigenesis and gemcitabine resistance by activating AKT in bladder cancer

KNSTRN is a component of the mitotic spindle, which was rarely investigated in tumorigenesis. AKT plays an essential role in tumorigenesis by modulating the phosphorylation of various substrates. The activation of AKT is regulated by PTEN and PIP₃. Here, we prove KNSTRN is positively correlated with malignancy of bladder cancer and KNSTRN activates AKT phosphorylation at Thr308 and Ser473. More importantly, our study reveals that both KNSTRN and PTEN interact with PH domain of AKT at cell membrane. The amount of KNSTRN interacted with AKT is negatively related to PTEN. Furthermore, PIP₃ pull-down assay proves that KNSTRN promoted AKT movement to PIP₃. These data suggest KNSTRN may activate AKT phosphorylation by promoting AKT movement to PIP₃ and alleviating PTEN suppression. Based on the activation of AKT phosphorylation, our study demonstrates that KNSTRN promotes bladder cancer metastasis and gemcitabine resistance in vitro and in vivo. Meanwhile, the effect of KNSTRN on tumorigenesis and gemcitabine resistance could be restored by AKT specific inhibitor MK2206 or AKT overexpression. In conclusion, we identify an oncogene KNSTRN that promotes tumorigenesis and gemcitabine resistance by activating AKT phosphorylation and may serve as a therapeutic target in bladder cancer.

Opportunities and challenges of fatty acid conjugated therapeutics

Instability, poor cellular uptake and unfavorable pharmacokinetics and biodistribution of many therapeutic molecules require modification in their physicochemical properties. The conjugation of these APIs with fatty acids has demonstrated an enhancement in their lipophilicity and stability. The improvement in the formulations that resulted from the conjugation of a drug with a fatty acid includes increased half-life, enhanced cellular uptake and retention, targeted tumor delivery, reduced chemoresistance in cancer, and improved blood-brain-barrier (BBB) penetration. In this review, various therapeutic molecules, including small molecules, peptides and oligonucleotides, that have been conjugated with fatty acid have been thoroughly discussed along with various conjugation strategies. The application of nano-system based delivery is gaining a lot of attention due to its ability to provide controlled drug release, targeting and reducing the extent of side effects. This review also covers various nano-carriers that have been utilized for the delivery of fatty acid drug conjugates. The enhanced lipophilicity of the drug-fatty acid conjugate has shown to enhance the affinity of the drug towards these carriers, thereby increasing the entrapment efficiency and formulation performance.

Immune-Based Therapies and the Role of Microsatellite Instability in Pancreatic Cancer

Pancreatic cancer is one of the most aggressive malignancies with limited treatment options thus resulting in high morbidity and mortality. Among all cancers, with a five-year survival rates of only 2-9%, pancreatic cancer holds the worst prognostic outcome for patients. To improve the overall survival, an earlier diagnosis and stratification of cancer patients for personalized treatment options are urgent needs. A minority of pancreatic cancers belong to the spectrum of Lynch syndrome-associated cancers and are characterized by microsatellite instability (MSI). MSI is a consequence of defective mismatch repair protein functions and it has been well characterized in other gastrointestinal tumors such as colorectal and gastric cancer. In the latter, high levels of MSI are linked to a better prognosis and to an increased benefit to immune-based therapies. Therefore, the same therapies could offer an opportunity of treatment for pancreatic cancer patients with MSI. In this review, we summarize the current knowledge about immune-based therapies and MSI in pancreatic cancer.

Inhibiting RRM2 to enhance the anticancer activity of chemotherapy

RRM2, the small subunit of ribonucleotide reductase, is identified as a tumor promotor and therapeutic target. It is common to see the overexpression of RRM2 in chemo-resistant cancer cells and patients. RRM2 mediates the resistance of many chemotherapeutic drugs and could become the predictor for chemosensitivity and prognosis. Therefore, inhibition of RRM2 may be an effective means to enhance the anticancer activity of chemotherapy. This review tries to discuss the mechanisms of RRM2 overexpression and the role of RRM2 in resistance to chemotherapy. Additionally, we compile the studies on small interfering RNA targets RRM2, RRM2 inhibitors, kinase inhibitors, and other ways that could overcome the resistance of chemotherapy or exert synergistic anticancer activity with chemotherapy through the expression inhibition or the enzyme inactivation of RRM2.

Gel-Based Nanocarrier for Intravesical Chemotherapy Delivery: In Vitro and In Vivo Study

Intravesical administration of chemotherapeutic agents can enhance drug accumulation in tumors and reduce systemic side effects. Nanocarriers were developed for intravesical administration and exploit the permeation enhancement effect. In vitro permeation evaluation, the drug transdermal amount and accumulation amounts in the tissue of gemcitabine-loaded nanocarriers through biological membrane significantly increased about 14.8~33.0-fold and 1.5~14.1-fold respectively, when compared to a control group of 1% gemcitabine saline solution. In in vivo intravesical administration, the drug accumulation amount in bladder tissue of nanocarrier of 75.2 ± 5.4 μg was revealed as being comparably higher than that of the control group of 44.8 ± 6.4 μg. In confocal laser scanning microscopy imagery, the penetration depth of fluorescent dyes-rhodamine was increased from 80 μm up to 120 μm when a nanocarrier was used. This result implies that the nanocarrier is a promising drug delivery agent for intravesical administration.

Co-Delivery of Cisplatin and Gemcitabine via Viscous Nanoemulsion for Potential Synergistic Intravesical Chemotherapy

Combined chemotherapy is an effective and safe treatment for cancers. Co-administration of cisplatin and gemcitabine produces a synergistic effect for bladder cancer treatment, so viscous microemulsions were developed for co-delivery of cisplatin and gemcitabine to extend the retention time and improve the permeability of chemotherapeutic drugs into the urothelium by intravesical administration. Results showed that the deposition amounts of cisplatin and gemcitabine significantly increased in in vitro and in vivo study. The penetration depth in bladder tissue samples increased from 60 to 120 μm. The dual-loaded formulation also showed thermodynamic and chemical stability, demonstrating that these gel-based microemulsions are promising drug delivery carriers for chemotherapy agents by intravesical administration.

Gemcitabine resistance in triple-negative breast cancer cells can be reverted by Drosophila melanogaster deoxyribonucleoside kinase in the nucleus or cytosol

The development of drug resistance to chemotherapeutic agents has consistently presented a challenge in terms of the treatment of patients with triple-negative breast cancer (TNBC). In the present study, gemcitabine (dFdC)-resistant TNBC cells were established, and the effects of lentivirus-deoxyribonucleoside kinase (dNK) and a mutated form of dNK (lentivirus-dNKmut) on reversing the acquired drug resistance in dFdC-resistant TNBC cells were explored. Quantitative PCR and western blotting experiment results suggested that Drosophila melanogaster (Dm)-dNK was stably expressed in the lentivirus-infected MDA-MB-231 and MDA-MB-231R cells in the nucleus or cytosol, and autoradiography experiments revealed similar levels of enzymatic activity in the cells expressing dNK or dNKmut. In vitro cytotoxicity assay revealed that the IC₅₀ values of dFdC were decreased 30~50-fold in the dFdC-resistant MDA-MB-231 cells following lentiviral transfection with dNK or dNKmut, and this effect was associated with a significantly increased rate of apoptosis compared with the cells transfected with the negative control lentivirus. In conclusion, Dm-dNK in the nucleus or cytosol may be a potential candidate for reversing acquired dFdC resistance in TNBC cells, which may form the basis of novel strategies for the treatment of patients with drug-resistant TNBC.

Penetrable Nanoplatform for "Cold" Tumor Immune Microenvironment Reeducation

Lack of tumor-infiltration lymphocytes (TILs) and resistances by overexpressed immunosuppressive cells (principally, myeloid-derived suppressor cells (MDSCs)) in tumor milieu are two major challenges hindering the effectiveness of immunotherapy for "immune-cold" tumors. In addition, the natural physical barrier existing in solid cancer also limits deeper delivery of drugs. Here, a tumor-targeting and light-responsive-penetrable nanoplatform (Apt/PDGs^s@pMOF) is developed to elicit intratumoral infiltration of cytotoxic T cells (CTLs) and reeducate immunosuppressive microenvironment simultaneously. In particular, porphyrinic metal-organic framework (pMOF)-based photodynamic therapy (PDT) induces tumor immunogenic cell death (ICD) to promote CTLs intratumoral infiltration and hot "immune-cold" tumor. Upon being triggered by PDT, the nearly 10 nm adsorbed drug-loaded dendrimer de-shields from the nanoplatform and spreads into the deeper tumor, eliminating MDSCs and reversing immunosuppression, eventually reinforcing immune response. Meanwhile, the designed nanoplatform also has a systemic MDSC inhibition effect and moderate improvement of overall antitumor immune responses, resulting in effective suppression of distal tumors within less significant immune-related adverse effects (irAEs) induced.

Gambogic acid potentiates gemcitabine induced anticancer activity in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most frequent type of lung cancer accounting up to 80-85% of all lung cancer (LC) cases. Gemcitabine (Gem), a pyrimidine nucleoside antimetabolite, is widely used chemotherapy offering several months survival benefit in patients with NSCLC. The emergence of Gem resistance is a main clinical concern in cancer treatment and thus a continuous demand for development of new therapeutic strategies to improve its antitumor activity. Hence, we report an adjuvant therapeutic regimen based on natural compound, gambogic acid (GA) which has been shown to enhanced Gem induced inhibition of cancer cell growth, arrest cell cycle, and induce apoptosis by enhanced accumulation of Gem. The in vitro cell viability, clonogenicity, invasion, and migration assays demonstrated a significant higher therapeutic effect of Gem when it was combined with GA in A549 and H1299 cells. A better access of internalization of drug molecules achieved in rhodamine 123 assay when GA was used as adjuvant treatment. Further, GA and Gem combination significantly reduced tubular formation of HUVEC cells indicates lowering angiogenesis potential. Microarray and Western blot studies confirm that GA + Gem co-treatment strategy promotes cancer cell death by downregulating anti-apoptotic proteins, chemoresistance-associated proteins, and upregulation of apoptosis proteins. More importantly, a significant higher therapeutic benefit was noticed for GA and Gem combination in A549 xenograft mice model. Together, these results offer a rationale to evaluate the clinical translational possibility of GA as adjuvant therapy to overcome Gem resistance. This combination regimen can be a new therapeutic concept to eradicate this devastating disease.

Characterization of PHGDH expression in bladder cancer: potential targeting therapy with gemcitabine/cisplatin and the contribution of promoter DNA hypomethylation

d‐3‐Phosphoglycerate dehydrogenase (PHGDH) conducts an important step in the synthesis of serine. Importantly, the PHGDH gene is often amplified in certain cancers. Our previous studies revealed that PHGDH gene amplification was associated with poor overall survival in clear cell renal cell carcinoma (ccRCC) and that metabolic reprogramming of serine synthesis through PHGDH recruitment allowed ccRCC cells to survive in unfavorable environments. There have been no investigations of the role of PHGDH expression in bladder cancer (BC). In this investigation, we examined the clinical importance of PHDGH in BC. Furthermore, we asked whether PHGDH expression could be exploited for BC therapy. Finally, we investigated the regulatory mechanisms that modulated the expression of PHGDH. Using data from The Cancer Genome Atlas, we found that patients with high‐grade BC had significantly higher PHGDH expression levels than did those with low‐grade BC. In addition, patients with high PHGDH expression did not survive as long as those with low expression. PHGDH downregulation by si‐RNAs or an inhibitor in BC cell lines significantly inhibited proliferative ability and induced apoptosis. Furthermore, combined treatment using a PHGDH inhibitor and gemcitabine/cisplatin achieved synergistic tumor suppression compared to use of a single agent both in vitro as well as in vivo. Mechanistic analyses of PHGDH regulation showed that PHGDH expression might be associated with DNA copy number and hypomethylation in BC. These findings suggest novel therapeutic strategies could be used in BC. Finally, our data enhance our understanding of the role of PHGDH in BC.

Cordycepin inhibits pancreatic cancer cell growth in vitro and in vivo via targeting FGFR2 and blocking ERK signaling

Cordycepin (3'-deoxyadenosine) from Cordyceps militaris has been reported to have anti-tumor effects. However, the molecular target and mechanism underlying cordycepin impeding pancreatic cancer cell growth in vitro and in vivo remain vague. In this study, we reported functional target molecule of cordycepin which inhibited pancreatic cancer cells growth in vitro and in vivo. Cordycepin was confirmed to induce apoptosis by activating caspase-3, caspase-9 and cytochrome c. Further studies suggested that MAPK pathway was blocked by cordycepin via inhibiting the expression of Ras and the phosphorylation of Erk. Moreover, cordycepin caused S-phase arrest and DNA damage associated with activating Chk2 (checkpoint kinase 2) pathway and downregulating cyclin A2 and CDK2 phosphorylation. Very interestingly, we showed that cordycepin could bind to FGFR2 (K_D = 7.77 × 10^-9) very potently to inhibit pancreatic cancer cells growth by blocking Ras/ErK pathway. These results suggest that cordycepin could potentially be a leading compound which targeted FGFR2 to inhibit pancreatic cells growth by inducing cell apoptosis and causing cell cycle arrest via blocking FGFR/Ras/ERK signaling for anti-pancreatic cancer new drug development.

A Pharmacokinetic and Pharmacodynamic Evaluation of the Anti-Hepatocellular Carcinoma Compound 4-N-Carbobenzoxy-gemcitabine (Cbz-dFdC)

Gemcitabine (dFdC) demonstrates significant effectiveness against solid tumors in vitro and in vivo; however, its clinical application is limited because it tends to easily undergo deamination metabolism. Therefore, we synthesized 4-N-carbobenzoxy-gemcitabine (Cbz-dFdC) as a lead prodrug and conducted a detailed pharmacokinetic, metabolic, and pharmacodynamic evaluation. After intragastric Cbz-dFdC administration, the C_max of Cbz-dFdC and dFdC was 451.1 ± 106.7 and 1656.3 ± 431.5 ng/mL, respectively. The T_max of Cbz-dFdC and dFdC was 2 and 4 h, respectively. After intragastric administration of Cbz-dFdC, this compound was mainly distributed in the intestine due to low carboxylesterase-1 (CES1) activity. Cbz-dFdC is activated by CES1 in both humans and rats. The enzyme kinetic curves were well fitted by the Michaelis–Menten equation in rats’ blood, plasma, and tissue homogenates and S9 of the liver and kidney, as well as human liver S9 and CES1 recombinase. The pharmacodynamic results showed that the Cbz-dFdC have a good antitumor effect in the HepG2 cell and in tumor-bearing mice, respectively. In general, Cbz-dFdC has good pharmaceutical characteristics and is therefore a good candidate for a potential prodrug.

Mechanistic Multiscale Pharmacokinetic Model for the Anticancer Drug 2',2'-difluorodeoxycytidine (Gemcitabine) in Pancreatic Cancer

The aim of this work is to build a mechanistic multiscale pharmacokinetic model for the anticancer drug 2’,2’‐difluorodeoxycytidine (gemcitabine, dFdC), able to describe the concentrations of dFdC metabolites in the pancreatic tumor tissue in dependence of physiological and genetic patient characteristics, and, more in general, to explore the capabilities and limitations of this kind of modeling strategy. A mechanistic model characterizing dFdC metabolic pathway (metabolic network) was developed using in vitro literature data from two pancreatic cancer cell lines. The network was able to describe the time course of extracellular and intracellular dFdC metabolites concentrations. Moreover, a physiologically‐based pharmacokinetic model was developed to describe clinical dFdC profiles by using enzymatic and physiological information available in the literature. This model was then coupled with the metabolic network to describe the dFdC active metabolite profile in the pancreatic tumor tissue. Finally, global sensitivity analysis was performed to identify the parameters that mainly drive the interindividual variability for the area under the curve (AUC) of dFdC in plasma and of its active metabolite (dFdCTP) in tumor tissue. From this analysis, cytidine deaminase (CDA) concentration was identified as the main driver of plasma dFdC AUC interindividual variability, whereas CDA and deoxycytidine kinase concentration mainly explained the tumor dFdCTP AUC variability. However, the lack of in vitro and in vivo information needed to characterize key model parameters hampers the development of this kind of mechanistic approach. Further studies to better characterize pancreatic cell lines and patient enzymes polymorphisms are encouraged to refine and validate the current model.

Development of gemcitabine-resistant patient-derived xenograft models of pancreatic ductal adenocarcinoma

AIM

Gemcitabine is a frontline agent for locally-advanced and metastatic pancreatic ductal adenocarcinoma (PDAC), but neither gemcitabine alone nor in combination produces durable remissions of this tumor type. We developed three PDAC patient-derived xenograft (PDX) models with gemcitabine resistance (gemR) acquired in vivo, with which to identify mechanisms of resistance relevant to drug exposure in vivo and to evaluate novel therapies.

METHODS

Mice bearing independently-derived PDXs received 100 mg/kg gemcitabine once or twice weekly. Tumors initially responded, but regrew on treatment and were designated gemR. We used immunohistochemistry to compare expression of proteins previously associated with gemcitabine resistance [ribonucleotide reductase subunit M1 (RRM1), RRM2, human concentrative nucleoside transporter 1 (hCNT1), human equilibrative nucleoside transporter 1 (hENT1), cytidine deaminase (CDA), and deoxycytidine kinase (dCK)] in gemR and respective gemcitabine-naive parental tumors.

RESULTS

Parental and gemR tumors did not differ in tumor cell morphology, amount of tumor-associated stroma, or expression of stem cell markers. No consistent pattern of expression of the six gemR marker proteins was observed among the models. Increases in RRM1 and CDA were consistent with in vitro-derived gemR models. However, rather than the expected decreases of hCNT1, hENT1, and dCK, gemR tumors expressed no change in or higher levels of these gemR marker proteins than parental tumors.

CONCLUSION

These models are the first PDAC PDX models with gemcitabine resistance acquired in vivo. The data indicate that mechanisms identified in models with resistance acquired in vitro are unlikely to be the predominant mechanisms when resistance is acquired in vivo. Ongoing work focuses on characterizing unidentified mechanisms of gemR and on identifying agents with anti-tumor efficacy in these gemR models.

A Novel E2F1-EP300-VMP1 Pathway Mediates Gemcitabine-Induced Autophagy in Pancreatic Cancer Cells Carrying Oncogenic KRAS

Autophagy is an evolutionarily preserved degradation process of cytoplasmic cellular constituents, which participates in cell response to disease. We previously characterized VMP1 (Vacuole Membrane Protein 1) as an essential autophagy related protein that mediates autophagy in pancreatic diseases. We also demonstrated that VMP1-mediated autophagy is induced by HIF-1A (hypoxia inducible factor 1 subunit alpha) in colon-cancer tumor cell lines, conferring resistance to photodynamic treatment. Here we identify a new molecular pathway, mediated by VMP1, by which gemcitabine is able to trigger autophagy in human pancreatic tumor cell lines. We demonstrated that gemcitabine requires the VMP1 expression to induce autophagy in the highly resistant pancreatic cancer cells PANC-1 and MIAPaCa-2 that carry activated KRAS. E2F1 is a transcription factor that is regulated by the retinoblastoma pathway. We found that E2F1 is an effector of gemcitabine-induced autophagy and regulates the expression and promoter activity of VMP1. Chromatin immunoprecipitation assays demonstrated that E2F1 binds to the VMP1 promoter in PANC-1 cells. We have also identified the histone acetyltransferase EP300 as a modulator of VMP1 promoter activity. Our data showed that the E2F1-EP300 activator/co-activator complex is part of the regulatory pathway controlling the expression and promoter activity of VMP1 triggered by gemcitabine in PANC-1 cells. Finally, we found that neither VMP1 nor E2F1 are induced by gemcitabine treatment in BxPC-3 cells, which do not carry oncogenic KRAS and are sensitive to chemotherapy. In conclusion, we have identified the E2F1-EP300-VMP1 pathway that mediates gemcitabine-induced autophagy in pancreatic cancer cells. These results strongly support that VMP1-mediated autophagy may integrate the complex network of events involved in pancreatic ductal adenocarcinoma chemo-resistance. Our experimental findings point at E2F1 and VMP1 as novel potential therapeutic targets in precise treatment strategies for pancreatic cancer.

DCK is an Unfavorable Prognostic Biomarker and Correlated With Immune Infiltrates in Liver Cancer

BACKGROUND

The biological function of deoxycytidine kinase in tumor is not yet clear, and there are a few studies relating to the correlation of deoxycytidine kinase gene with the occurrence and development of liver cancer.

METHODS

The messenger RNA expression of deoxycytidine kinase was analyzed with the use of the UALCAN and GEPIA database. Moreover, we assessed the function of deoxycytidine kinase on clinical prognosis with Kaplan-Meier plotter database. The relationship between deoxycytidine kinase and cancer immune infiltrates was investigated via Tumor Immune Estimation Resource site. Furthermore, Tumor Immune Estimation Resource was also used to evaluate the correlations between the expression of deoxycytidine kinase and gene marker sets of immune infiltrates.

RESULTS

The deoxycytidine kinase messenger RNA level significantly upregulated in patients with liver cancer compared to normal liver samples. Moreover, the increased expression of deoxycytidine kinase messenger RNA was closely associated with reduced overall survival and disease-free survival in all liver cancers. In addition, deoxycytidine kinase expression displayed a strong correlation with infiltrating levels of macrophages, neutrophils, and dendritic cells in liver cancer, and deoxycytidine kinase expression was positively correlated with diverse immune marker sets in liver cancer.

CONCLUSIONS

All the above findings suggested that increased expression of deoxycytidine kinase was significantly related to unfavorable prognosis in patients with liver cancer. And deoxycytidine kinase is correlated with immune infiltrating levels, including those of B cells, macrophages, neutrophils, and dendritic cells in patients with liver cancer. These findings suggest that deoxycytidine kinase can be used as a prognostic biomarker for determining prognosis and immune infiltration in liver cancer. And deoxycytidine kinase is a potential target for liver cancer therapy, and these preliminary findings require further study to determine whether deoxycytidine kinase-targeting reagents might be developed for clinical application in liver cancer.

Recombinant deoxyribonucleoside kinase from Drosophila melanogaster can improve gemcitabine based combined gene/chemotherapy for targeting cancer cells

A recombinant deoxyribonucleoside kinase from Drosophila melanogaster with a deletion of the last 20 amino acid residues (named DmdNKΔC20) was hypothesized as a potential therapeutic tool for gene therapy due to its broad substrate specificity and better catalytic efficiency towards nucleosides and nucleoside analogs. This study was designed to evaluate the effect of DmdNKΔC20 for sensitizing human cancer cell lines to gemcitabine and to further investigate its role in reversal of acquired drug resistance in gemcitabine-resistant cancer cell line. The DmdNKΔC20 gene was delivered to three different cancer cell lines, including breast, colon and liver cancer cells, using lipid-mediated transfection reagent. After transfection, gene expression of DmdNKΔC20 was confirmed by quantitative reverse transcription PCR (qRT-PCR) and the combined effect of DmdNKΔC20 and gemcitabine based cytotoxicity was observed by cell viability assay. We further evolved a gemcitabine-resistant breast cancer cell line (named MCF7-R) through directed evolution in the laboratory, which showed 375-fold more resistance compared with parental MCF7 cells. Upon transfection with DmdNKΔC20 gene, MCF7-R cells showed 83-fold higher sensitivity to gemcitabine compared with the control group of MCF7-R cells. Moreover, we observed 79% higher expression of p21 protein in transfected MCF7-R cells, which may indicate induction of apoptosis. Our findings highlight the importance and therapeutic potential of DmdNKΔC20 in combined gene/chemotherapy approach to target a wide range of cancers, particularly gemcitabine-resistant cancers.

Chemoresistance in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC), generally known as pancreatic cancer (PC), ranks the fourth leading cause of cancer-related deaths in the western world. While the incidence of pancreatic cancer is displaying a rising tendency every year, the mortality rate has not decreased significantly because of late diagnosis, early metastasis, and limited reaction to chemotherapy or radiotherapy. Adjuvant chemotherapy after surgical resection is typically the preferred option to treat early pancreatic cancer. Although 5-fluorouracil/leucovorin with irinotecan and oxaliplatin (FOLFIRINOX) and gemcitabine/nab-paclitaxel can profoundly improve the prognosis of advanced pancreatic cancer, the development of chemoresistance still leads to poor clinical outcomes. Chemoresistance is multifactorial as a result of the interaction among pancreatic cancer cells, cancer stem cells, and the tumor microenvironment. Nevertheless, more pancreatic cancer patients will benefit from precision treatment and targeted drugs. Therefore, we outline new perspectives for enhancing the efficacy of gemcitabine after reviewing the related factors of gemcitabine metabolism, mechanism of action, and chemoresistance.