Efficacy and safety of pyrotinib combined with albumin-bound paclitaxel as first-line treatment for HER2-positive metastatic breast cancer in patients previously treated with adjuvant and/or neoadjuvant trastuzumab therapy: The stage 1 results of a single-arm, phase 2 prospective clinical trial

OBJECTIVE

It has been observed that the prognosis of patients with HER2-positive metastatic breast cancer has improved significantly with HER2-targeted agents. However, there is still a lack of evidence regarding first-line anti-HER2 treatment options for patients who have received adjuvant and/or neoadjuvant trastuzumab for HER2-positive metastatic breast cancer. Besides, there are no reliable markers that can predict the efficacy of anti-HER2 treatment in these patients.

METHODS

Patients who have received adjuvant and/or neoadjuvant trastuzumab for HER2-positive metastatic breast cancer were enrolled. Pyrotinib plus albumin-bound paclitaxel were used as first-line treatment. The primary endpoint was the objective response rate (ORR). The safety profile was also assessed. In order to explore predictive biomarkers using Olink technology, blood samples were collected dynamically.

RESULTS

From December 2019 to August 2023, the first stage of the study involved 27 eligible patients. It has not yet reached the median PFS despite the median follow-up being 17.8 months. Efficacy evaluation showed that the ORR was 92.6%, and the DCR was 100%. Adverse events of grade 3 or higher included diarrhoea (29.6%), leukopenia (11.1%), neutropenia (25.9%), oral mucositis (3.7%), and hand-foot syndrome (3.7%). Toll-like receptor 3 (TLR3) and Proto-oncogene tyrosine-protein kinase receptor (RET) were proteins with significant relevance to PFS in these patients.

CONCLUSIONS

This study demonstrates that pyrotinib plus albumin-bound paclitaxel as a first-line treatment regimen shows good efficacy and manageable safety for patients who have received adjuvant and/or neoadjuvant trastuzumab for HER2-positive metastatic breast cancer. Besides, a significant association was identified between the expression levels of TLR3 and RET and the PFS in patients.

SiATG5-loaded cancer cell membrane-fused liposomes induced increased uptake of albumin-bound chemotherapeutics by pancreatic cancer cells

Chemotherapeutic efficacy for pancreatic cancer is severely compromised by limited drug availability to tumor cells. Herein, we constructed a cancer cell membrane-fused liposome containing a siATG5-loaded calcium phosphate (CaP) core, termed CLip@siATG5. Through cancer cell membrane camouflage, the liposomes evaded immune clearance, actively infiltrated tumor tissues, and were preferentially taken up by homotypic tumor cells. Then, siATG5 escaped from the endosomes and was liberated in the cytoplasm, mainly benefiting from CaP dissolution-induced endosome rupture and liposome disassembly in acidic endosomes. The released siATG5 silenced autophagy protein 5 (ATG5) to inhibit autophagy, starving tumor cells. An alternative nutrient procurement pathway, macropinocytosis, was then upregulated in the cells, leading to increased uptake of the albumin-bound chemotherapeutic agent (nanoparticle albumin-bound paclitaxel (Nab-PTX)). Finally, in a murine pancreatic cancer model, CLip@siATG5 combined with Nab-PTX exerted superior efficacy to a twofold dose of Nab-PTX while avoiding its toxicity. Overall, we justified enhancing chemotherapeutic delivery by modulating the pancreatic cancer cell metabolism, which will enlighten the development of more effective chemotherapeutic adjuvants for pancreatic cancer in the future.

Albumin-bound paclitaxel augment temozolomide treatment sensitivity of glioblastoma cells by disrupting DNA damage repair and promoting ferroptosis

BACKGROUND

Temozolomide (TMZ) treatment efficacy in glioblastoma (GBM) patients has been limited by resistance in the clinic. Currently, there are no clinically proven therapeutic options available to restore TMZ treatment sensitivity. Here, we investigated the potential of albumin-bound paclitaxel (ABX), a novel microtubule targeting agent, in sensitizing GBM cells to TMZ and elucidated its underlying molecular mechanism.

METHODS

A series of in vivo and in vitro experiments based on two GBM cell lines and two primary GBM cells were designed to evaluate the efficacy of ABX in sensitizing GBM cells to TMZ. Further proteomic analysis and validation experiments were performed to explore the underlying molecular mechanism. Finally, the efficacy and mechanism were validated in GBM patients derived organoids (PDOs) models.

RESULTS

ABX exhibited a synergistic inhibitory effect on GBM cells when combined with TMZ in vitro. Combination treatment of TMZ and ABX was highly effective in suppressing GBM progression and significantly prolonged the survival oforthotopic xenograft nude mice, with negligible side effects. Further proteomic analysis and experimental validation demonstrated that the combined treatment of ABX and TMZ can induce sustained DNA damage by disrupting XPC and ERCC1 expression and nuclear localization. Additionally, the combination treatment can enhance ferroptosis through regulating HOXM1 and GPX4 expression. Preclinical drug-sensitivity testing based on GBM PDOs models confirmed that combination therapy was significantly more effective than conventional TMZ monotherapy.

CONCLUSION

Our findings suggest that ABX has the potential to enhance TMZ treatment sensitivity in GBM, which provides a promising therapeutic strategy for GBM patients.

pH-sensitive nanomedicine of novel tubulin polymerization inhibitor for lung metastatic melanoma

Microtubule binding agents such as paclitaxel and vincristine have activity in metastatic melanoma. However, even responsive tumors develop resistance, highlighting the need to investigate new drug molecules. Here, we showed that a new compound, CH-2-102, developed by our group, has high anti-tumor efficacy in human and murine melanoma cells. We confirmed that CH-2-102 robustly suppresses the microtubule polymerization process by directly interacting with the colchicine binding site. Our results unveil that CH-2-102 suppresses microtubule polymerization and subsequently induces G2 phase cell arrest as one of the possible mechanisms. Notably, CH-2-102 maintains its efficacy even in the paclitaxel resistance melanoma cells due to different binding sites and a non-Pgp substrate. We developed a pH-responsive drug-polymer Schiff bases linker for high drug loading into nanoparticles (NPs). Our CH-2-102 conjugated NPs induced tumor regression more effectively than Abraxane® (Nab-paclitaxel, N-PTX), free drug, and non-sensitive NPs in B16-F10 cell-derived lung metastasis mouse model. Furthermore, our results suggest that the formulation has a high impact on the in vivo efficacy of the drug and warrants further investigation in other cancers, particularly taxane resistant. In conclusion, the microtubule polymerization inhibitor CH-2-102 conjugated pH-responsive NPs induce tumor regression in lung metastasis melanoma mice, suggesting it may be an effective strategy for treating metastatic melanoma.

SOX8 Affects Tumoral SPARC Expression by Regulating EZH2 to Attenuate Effectiveness of albumin-bound paclitaxel in PDAC

Pancreatic cancer is a dismal malignancy with poor prognosis. In spite of progress in surgical technology, chemotherapy is still the cornerstone in the multi-disciplinary treatment. Albumin-bound paclitaxel is a first-line treatment for PDAC patients. Yet the response rate of the drug is far from satisfying. SOX8 is a member of the sex determining region Y-boxes family, which is potentially related to the chemoresistance of tumor. Patient with high expression of SOX8 were insensitive to albumin-bound paclitaxel. SOX8 reduced apoptosis and G2/M cell cycle arrest caused by albumin-bound paclitaxel. SOX8 transcriptionally regulated EZH2, which reduced expression of SPARC by promoting the methylation of SPARC, thereby reducing the transport of albumin-bound paclitaxel in pancreatic cancer cells. EZH2 inhibitor, UNC1999, can reverse the effect of SOX8 on chemo-resistance of albumin-bound paclitaxel. Collectively, our data revealed SOX8/EZH2/SPARC signaling induced primary chemo-resistance of albumin-bound paclitaxel in pancreatic ductal adenocarcinoma.

Cell metabolomics analyses revealed a role of altered fatty acid oxidation in neurotoxicity pattern difference between nab-paclitaxel and solvent-based paclitaxel

Peripheral neuropathy (PN) is a dose-limiting, painful adverse reaction associated with the use of paclitaxel. This common side effect was often partially attributed to the solvent used for solubilization of the highly hydrophobic drug substance. Therefore, the development of alternative formulations thrived, which included that of Abraxane® containing nanoparticle albumin-bound paclitaxel (nab-paclitaxel). However, studies demonstrated inconsistent conclusions regarding the mitigation of PN in comparison with the traditional formulation. The mass spectrometry-based cell metabolomics approach was used in the present study to explore the potentially associated mechanisms. Although no significant difference in the effects on cell viability was observed, fold changes in carnitine, several acylcarnitines and long-chain fatty acid(s) were significantly different between treatment groups in differentiated and undifferentiated SH-SY5Y cells. The most prominent difference observed was the significant increase of octanoylcarnitine in cells treated with solvent-based paclitaxel, which was found to be associated with significant decrease of medium-chain acyl-CoA dehydrogenase (MCAD). The findings suggested the potential role of altered fatty acid oxidation in the different neurotoxicity patterns observed, which may be a possible target for therapeutic interventions worth further investigation.

Efficacy of albumin-bound paclitaxel in the treatment of advanced refractory breast cancer and its effect on serum resistin

PURPOSE

This study aimed to investigate the efficacy of albumin-bound paclitaxel (nab-paclitaxel) in the treatment of advanced refractory breast cancer (BC) and its effect on serum resistin.

METHODS

A retrospective study was performed based on the clinical records of 95 patients with advanced refractory BC admitted to Weihai Central Hospital from March 2012 to May 2015. Thirty-four patients were treated with traditional paclitaxel and enrolled in the control group, while the other 61 patients were treated with nab-paclitaxel and enrolled in the study group. The efficacy, toxicity and side effects, quality of life, and serum resistin levels were compared between the two groups.

RESULTS

The total response rate (RR) of the study group was much higher than that of the control group (p<0.05). The leukopenia level of the study group during the treatment was significantly lower than that of the control group (p<0.05). The level of serum resistin in the study group after treatment was significantly lower than in the control group (p<0.05). The improvement rate of quality of life in the study group was significantly higher than in the control group (p<0.05).

CONCLUSION

The results indicated that nab-paclitaxel is very effective in treating advanced refractory BC and reduces the level of serum resistin. It can improve the quality of life of patients and is worthy of clinical promotion.

Efficacy and safety of nanoparticle-albumin-bound paclitaxel compared with solvent-based taxanes for metastatic breast cancer: A meta-analysis

The curative effects of nanoparticle albumin-bound (nab)-paclitaxel in the first-line treatment of metastatic breast cancer (MBC) are still controversial, with even more after the removal of marketing approval of indication of bevacizumab. Five electronic databases and the related resources were searched for eligible randomized clinical trials (RCTs) without year and language restrictions to perform a meta-analysis. The studies were comparing the efficacy and safety between nab-paclitaxel chemotherapy versus solvent-based (sb)-taxanes chemotherapy such as sb-paclitaxel and docetaxel. The primary end points were overall response rate (ORR) and disease control rate (DCR). Secondary end points were progression-free survival (PFS), overall survival (OS), adverse events (AEs), and dose discontinuation rate (DDR). Five RCTs (1,554 patients) were finally identified from 1,902 studies. When compared to sb-paclitaxel, nab-paclitaxel showed significant beneficial effects in terms of ORR (OR 2.39, 95% CI 1.69-3.37, p < 0.001), DCR (OR 1.89, 95% CI 1.07-3.35, p = 0.03), and PFS (HR 0.75, 95% CI 0.62-0.90, p = 0.002). Nab-paclitaxel also showed significantly longer OS (HR 0.73, 95% CI 0.54-0.99, p = 0.04) than docetaxel. AEs and DDR were comparable between the two arms. Using nab-paclitaxel could significantly improve efficacy with comparable toxicities in the treatment of MBC.

Neoadjuvant Chemotherapy Based on Abraxane/Human Neutrophils Cytopharmaceuticals with Radiotherapy for Gastric Cancer

Gastric cancer remains one of the most lethal cancers with high incidence and mortality worldwide. The majority of gastric cancer patients are those who have first been diagnosed in advanced stage, in which the standard chemo-radiotherapy produces limited benefit along with severe general toxicity, thus the demand for improved therapeutic efficacy and decreased side effects drives the development of novel therapeutic strategies. Here, a neoadjuvant chemotherapy based on Abraxane/human neutrophils (NEs) cytopharmaceuticals with radiotherapy is presented for effective cancer treatment. Human NEs, the most abundant white blood cells in peripheral blood, are developed to carry Abraxane, the commercial albumin-bound paclitaxel nanoparticle, to form cytopharmaceuticals (Abraxane/NEs) which have been confirmed to maintain the intrinsic functions of human NEs. The modest radiation is applied not only to exert tumor disruption, but also to increase the release of inflammatory factors which guide the NEs homing to the tumoral sites. These amplified inflammatory factors at tumor sites excessively activate Abraxane/NEs to form neutrophil extracellular traps, along with a burst release of Abraxane to induce superior tumor suppression. This adjuvant chemo-radiotherapy based on cytopharmaceuticals may provide new opportunities for advanced cancer treatment, which reveals the huge clinical potential of human neutrophils as drug delivery vectors.

Development of biocompatible and VEGF-targeted paclitaxel nanodrugs on albumin and graphene oxide dual-carrier for photothermal-triggered drug delivery in vitro and in vivo

In this study, we performed the characterization and synthesis of biocompatible and targeted albumin and graphene oxide (GO) dual-carrier paclitaxel (PTX) nanoparticles for photothermal-triggered tumor therapy. PTX absorbed on GO nanosheets as cores were coated with human serum albumin (HSA), following surface conjugation with monoclonal antibodies (mAb) against vascular endothelial growth factor (VEGF; denoted as mAbVEGF) via polyethylene glycol linker to form targeted nanoparticles (PTX-GHP-VEGF). The spherical nanoparticles were 191±5 nm in size with good stability and biocompatibility. GO functioned as the first carrier and a near infrared absorber that can generate photothermal effects under 5-minute 808-nm laser irradiation to thermal trigger the release of PTX from the second carrier HSA nanoparticles. The mechanism of thermal-triggered drug release was also investigated preliminarily, in which the heat generated by GO induced swelling of PTX-GHP-VEGF nanoparticles which released the drugs. In vitro studies found that PTX-GHP-VEGF can efficiently target human SW-13 adrenocortical carcinoma cells as evaluated by confocal fluorescence microscopy as well as transmission electron microscopy, and showed an obvious thermal-triggered antitumor effect, mediated by apoptosis. Moreover, PTX-GHP-VEGF combined with near infrared irradiation showed specific tumor suppression effects with high survival rate after 100 days of treatment. PTX-GHP-VEGF also demonstrated high biosafety with no adverse effects on normal tissues and organs. These results highlight the remarkable potential of PTX-GHP-VEGF in photothermal controllable tumor treatment.

Transient tissue priming via ROCK inhibition uncouples pancreatic cancer progression, sensitivity to chemotherapy, and metastasis

The emerging standard of care for patients with inoperable pancreatic cancer is a combination of cytotoxic drugs gemcitabine and Abraxane, but patient response remains moderate. Pancreatic cancer development and metastasis occur in complex settings, with reciprocal feedback from microenvironmental cues influencing both disease progression and drug response. Little is known about how sequential dual targeting of tumor tissue tension and vasculature before chemotherapy can affect tumor response. We used intravital imaging to assess how transient manipulation of the tumor tissue, or "priming," using the pharmaceutical Rho kinase inhibitor Fasudil affects response to chemotherapy. Intravital Förster resonance energy transfer imaging of a cyclin-dependent kinase 1 biosensor to monitor the efficacy of cytotoxic drugs revealed that priming improves pancreatic cancer response to gemcitabine/Abraxane at both primary and secondary sites. Transient priming also sensitized cells to shear stress and impaired colonization efficiency and fibrotic niche remodeling within the liver, three important features of cancer spread. Last, we demonstrate a graded response to priming in stratified patient-derived tumors, indicating that fine-tuned tissue manipulation before chemotherapy may offer opportunities in both primary and metastatic targeting of pancreatic cancer.

DCE-MRI-Derived Parameters in Evaluating Abraxane-Induced Early Vascular Response and the Effectiveness of Its Synergistic Interaction with Cisplatin

Our previous studies revealed molecular alterations of tumor vessels, varying from immature to mature alterations, resulting from Abraxane, and demonstrated that the integrin-specific PET tracer 18F-FPPRGD2 can be used to noninvasively monitor such changes. However, changes in the tumor vasculature at functional levels such as perfusion and permeability are also important for monitoring Abraxane treatment outcomes in patients with cancer. The purpose of this study is to further investigate the vascular response during Abraxane therapy and the effectiveness of its synergistic interaction with cisplatin using Dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI). Thirty MDA-MB-435 tumor mice were randomized into three groups: PBS control (C group), Abraxane only (A group), and sequential treatment with Abraxane followed by cisplatin (A-P group). Tumor volume was monitored based on caliper measurements. A DCE-MRI protocol was performed at baseline and day 3. The Ktrans, Kep and Ve were calculated and compared with CD31, α-SMA, and Ki67 histology data. Sequential treatment with Abraxane followed by cisplatin produced a significantly greater inhibition of tumor growth during the three weeks of the observation period. Decreases in Ktrans and Kep for the A and A-P groups were observed on day 3. Immunohistological staining suggested vascular remodeling during the Abraxane therapy. The changes in Ktrans and Kep values were correlated with alterations in the permeability of the tumor vasculature induced by the Abraxane treatment. In conclusion, Abraxane-mediated permeability variations in tumor vasculature can be quantitatively visualized by DCE-MRI, making this a useful method for studying the effects of early cancer treatment, especially the early vascular response. Vascular remodeling by Abraxane improves the efficiency of cisplatin delivery and thus results in a favorable treatment outcome.

Paclitaxel-Loaded TPGS-b-PCL Nanoparticles: In Vitro Cytotoxicity and Cellular Uptake in MCF-7 and MDA-MB-231 Cells versus mPEG-b-PCL Nanoparticles and Abraxane®

Nanomedicines have become an attractive platform for the development of novel drug delivery systems in cancer chemotherapy. Polymeric nanoparticles (NPs) represent one of the best well-investigated nanosized carriers for delivery of antineoplastic compounds. The "Pegylation strategy" of drug delivery systems has been used in order to improve carrier biodistribution, however, some nanosized systems with PEG on their surface have exhibited poorly-cellular drug internalization. In this context, the purpose of the present study was to compare in vitro performance of two paclitaxel (PTX)-loaded NPs systems based on two biocompatible copolymers of alpha tocopheryl polyethylene glycol 1000 succinate-block-poly(ε-caprolactone) (TPGS-b-PCL) and methoxyPEG- block-poly(ε-caprolactone) (mPEG-b-PCL) in terms of citotoxicity and PTX cellular uptake. Fur- thermore, TPGS-b-PCL NPs were also copared with the commercially available PTX nano-sized formulation Abraxane®. Both TPGS-b-PCL and mPEG-b-PCL derivates were synthesized by ring opening polymerization of ε-caprolactone employing microwaved radiation. NPs were obtained by a solvent evaporation technique where the PTX content was determined by reverse-phase HPLC. The resulting NPs had an average size between 200 and 300 nm with a narrow size distribution. Also both NPs systems showed a spherical shape. The in vitro PTX release profile from the NPs was characterized employing the dialysis membrane method where all drug-loaded formulations showed a sustained and slow release of PTX. Finally, in vitro assays demonstrated that PTX-loaded TPGS- b-PCL exhibited a significant higher antitumor activity than PTX-loaded mPEG-b-PCL NPs and Abraxane® against an estrogen-dependent (MCF-7) and an estrogen independent (MDA-MB-231) breast cancer cells lines. Furthermore TPGS-b-PCL NPs showed a significant increase on PTX cellular uptake, for both breast cell lines, in comparison with mPEG-b-PCL NPs and Abraxane®. Overall findings confirmed that NPs based on TPGS-b-PCL as biomaterial demonstrated a better in vitro performance than NPs with PEG, representing an attractive alternative for the development of novel nanosized carriers for anticancer therapy.

Sensitivity of Human Intrahepatic Cholangiocarcinoma Subtypes to Chemotherapeutics and Molecular Targeted Agents: A Study on Primary Cell Cultures

We investigated the sensitivity of intrahepatic cholangiocarcinoma (IHCCA) subtypes to chemotherapeutics and molecular targeted agents. Primary cultures of mucin- and mixed-IHCCA were prepared from surgical specimens (N. 18 IHCCA patients) and evaluated for cell proliferation (MTS assay) and apoptosis (Caspase 3) after incubation (72 hours) with increasing concentrations of different drugs. In vivo, subcutaneous human tumor xenografts were evaluated. Primary cultures of mucin- and mixed-IHCCA were characterized by a different pattern of expression of cancer stem cell markers, and by a different drug sensitivity. Gemcitabine and the Gemcitabine-Cisplatin combination were more active in inhibiting cell proliferation in mixed-IHCCA while Cisplatin or Abraxane were more effective against mucin-IHCCA, where Abraxane also enhances apoptosis. 5-Fluoracil showed a slight inhibitory effect on cell proliferation that was more significant in mixed- than mucin-IHCCA primary cultures and, induced apoptosis only in mucin-IHCCA. Among Hg inhibitors, LY2940680 and Vismodegib showed slight effects on proliferation of both IHCCA subtypes. The tyrosine kinase inhibitors, Imatinib Mesylate and Sorafenib showed significant inhibitory effects on proliferation of both mucin- and mixed-IHCCA. The MEK 1/2 inhibitor, Selumetinib, inhibited proliferation of only mucin-IHCCA while the aminopeptidase-N inhibitor, Bestatin was more active against mixed-IHCCA. The c-erbB2 blocking antibody was more active against mixed-IHCCA while, the Wnt inhibitor, LGK974, similarly inhibited proliferation of mucin- and mixed-IHCCA. Either mucin- or mixed-IHCCA showed high sensitivity to nanomolar concentrations of the dual PI3-kinase/mTOR inhibitor, NVP-BEZ235. In vivo, in subcutaneous xenografts, either NVP-BEZ235 or Abraxane, blocked tumor growth. In conclusion, mucin- and mixed-IHCCA are characterized by a different drug sensitivity. Cisplatin, Abraxane and the MEK 1/2 inhibitor, Selumetinib were more active against mucin-IHCCA while, Gemcitabine, Gemcitabine-Cisplatin combination, the c-erbB2 blocking antibody and bestatin worked better against mixed-IHCCA. Remarkably, we identified a dual PI3-kinase/mTOR inhibitor that both in vitro and in vivo, exerts dramatic antiproliferative effects against both mucin- and mixed-IHCCA.

Quantitative Proteomic Analysis of Cellular Resistance to the Nanoparticle Abraxane

Abraxane, an FDA-approved albumin-bound nanoparticle (NP) form of paclitaxel (PTX) to treat breast cancer and nonsmall cell lung cancer (NSCLC), has been demonstrated to be more effective than the original Taxol, the single molecule form. We have established a cell line from NSCLC A549 cells to be resistant to Abraxane. To further understand the molecular mechanisms involved in the NP drug resistance, global protein expression profiles of Abraxane sensitive (A549) and resistant cells (A549/Abr), along with the treatment of Abraxane, have been obtained by a quantitative proteomic approach. The most significantly differentially expressed proteins are associated with lipid metabolism, cell cycle, cytoskeleton, apoptosis pathways and processes, suggesting several mechanisms are working synergistically in A549 Abraxane-resistant cells. Overexpression of proteins in the lipid metabolism processes, such as E3 ubiquitin-protein ligase RNF139 (RNF139) and Hydroxymethylglutaryl-CoA synthase (HMGCS1), have not been reported previously in the study of paclitaxel resistance, suggesting possibly different mechanism between nanoparticle and single molecular drug resistance. In particular, RNF139 is one of the most up-regulated proteins in A549 Abraxane-resistant cell line, but remains no change when the resistant cells were further treated with Abraxane and down-regulated in the sensitive cells after 4 h treatment of Abraxane. This study shows the use of a proteomic strategy to understand the unique response of drug resistant cells to a nanoparticle therapeutic.

A rapid in vivo screen for pancreatic ductal adenocarcinoma therapeutics

Pancreatic ductal adenocarcinoma (PDA) is the fourth leading cause of cancer-related deaths in the United States, and is projected to be second by 2025. It has the worst survival rate among all major cancers. Two pressing needs for extending life expectancy of affected individuals are the development of new approaches to identify improved therapeutics, addressed herein, and the identification of early markers. PDA advances through a complex series of intercellular and physiological interactions that drive cancer progression in response to organ stress, organ failure, malnutrition, and infiltrating immune and stromal cells. Candidate drugs identified in organ culture or cell-based screens must be validated in preclinical models such as KIC (p48(Cre);LSL-Kras(G12D);Cdkn2a(f/f)) mice, a genetically engineered model of PDA in which large aggressive tumors develop by 4 weeks of age. We report a rapid, systematic and robust in vivo screen for effective drug combinations to treat Kras-dependent PDA. Kras mutations occur early in tumor progression in over 90% of human PDA cases. Protein kinase and G-protein coupled receptor (GPCR) signaling activates Kras. Regulators of G-protein signaling (RGS) proteins are coincidence detectors that can be induced by multiple inputs to feedback-regulate GPCR signaling. We crossed Rgs16::GFP bacterial artificial chromosome (BAC) transgenic mice with KIC mice and show that the Rgs16::GFP transgene is a Kras(G12D)-dependent marker of all stages of PDA, and increases proportionally to tumor burden in KIC mice. RNA sequencing (RNA-Seq) analysis of cultured primary PDA cells reveals characteristics of embryonic progenitors of pancreatic ducts and endocrine cells, and extraordinarily high expression of the receptor tyrosine kinase Axl, an emerging cancer drug target. In proof-of-principle drug screens, we find that weanling KIC mice with PDA treated for 2 weeks with gemcitabine (with or without Abraxane) plus inhibitors of Axl signaling (warfarin and BGB324) have fewer tumor initiation sites and reduced tumor size compared with the standard-of-care treatment. Rgs16::GFP is therefore an in vivo reporter of PDA progression and sensitivity to new chemotherapeutic drug regimens such as Axl-targeted agents. This screening strategy can potentially be applied to identify improved therapeutics for other cancers.

Abraxane, the Nanoparticle Formulation of Paclitaxel Can Induce Drug Resistance by Up-Regulation of P-gp

P-glycoprotein (P-gp) can actively pump paclitaxel (PTX) out of cells and induces drug resistance. Abraxane, a nanoparticle (NP) formulation of PTX, has multiple clinical advantages over the single molecule form. However, it is still unclear whether Abraxane overcomes the common small molecule drug resistance problem mediated by P-gp. Here we were able to establish an Abraxane-resistant cell line from the lung adenocarcinoma cell line A549. We compared the transcriptome of A549/Abr resistant cell line to that of its parental cell line using RNA-Seq technology. Several pathways were found to be up or down regulated. Specifically, the most significantly up-regulated gene was ABCB1, which translates into P-glycoprotein. We verified the overexpression of P-glycoprotein and confirmed its function by reversing the drug resistance with P-gp inhibitor Verapamil. The results suggest that efflux pathway plays an important role in the Abraxane-resistant cell line we established. However, the relevance of this P-gp mediated Abraxane resistance in tumors of lung cancer patients remains unknown.