Disruption of FDPS/Rac1 axis radiosensitizes pancreatic ductal adenocarcinoma by attenuating DNA damage response and immunosuppressive signalling

Background

Radiation therapy (RT) has a suboptimal effect in patients with pancreatic ductal adenocarcinoma (PDAC) due to intrinsic and acquired radioresistance (RR). Comprehensive bioinformatics and microarray analysis revealed that cholesterol biosynthesis (CBS) is involved in the RR of PDAC. We now tested the inhibition of the CBS pathway enzyme, farnesyl diphosphate synthase (FDPS), by zoledronic acid (Zol) to enhance radiation and activate immune cells.

Methods

We investigated the role of FDPS in PDAC RR using the following methods: in vitro cell-based assay, immunohistochemistry, immunofluorescence, immunoblot, cell-based cholesterol assay, RNA sequencing, tumouroids (KPC-murine and PDAC patient-derived), orthotopic models, and PDAC patient's clinical study.

Findings

FDPS overexpression in PDAC tissues and cells (P < 0.01 and P < 0.05) is associated with poor RT response and survival (P = 0.024). CRISPR/Cas9 and pharmacological inhibition (Zol) of FDPS in human and mouse syngeneic PDAC cells in conjunction with RT conferred higher PDAC radiosensitivity in vitro (P < 0.05, P < 0.01, and P < 0.001) and in vivo (P < 0.05). Interestingly, murine (P = 0.01) and human (P = 0.0159) tumouroids treated with Zol+RT showed a significant growth reduction. Mechanistically, RNA-Seq analysis of the PDAC xenografts and patients-PBMCs revealed that Zol exerts radiosensitization by affecting Rac1 and Rho prenylation, thereby modulating DNA damage and radiation response signalling along with improved systemic immune cells activation. An ongoing phase I/II trial (NCT03073785) showed improved failure-free survival (FFS), enhanced immune cell activation, and decreased microenvironment-related genes upon Zol+RT treatment.

Interpretation

Our findings suggest that FDPS is a novel radiosensitization target for PDAC therapy. This study also provides a rationale to utilize Zol as a potential radiosensitizer and as an immunomodulator in PDAC and other cancers.

Funding

National Institutes of Health (P50, P01, and R01).

Global analysis of human glycosyltransferases reveals novel targets for pancreatic cancer pathogenesis

BACKGROUND

Several reports have shown the role of glycosylation in pancreatic cancer (PC), but a global systematic screening of specific glycosyltransferases (glycoTs) in its progression remains unknown.

METHODS

We demonstrate a rigorous top-down approach using TCGA-based RNA-Seq analysis, multi-step validation using RT-qPCR, immunoblots and immunohistochemistry. We identified six unique glycoTs (B3GNT3, B4GALNT3, FUT3, FUT6, GCNT3 and MGAT3) in PC pathogenesis and studied their function using CRISPR/Cas9-based KD systems.

RESULTS

Serial metastatic in vitro models using T3M4 and HPAF/CD18, generated in house, exhibited decreases in B3GNT3, FUT3 and GCNT3 expression on increasing metastatic potential. Immunohistochemistry identified clinical significance for GCNT3, B4GALNT3 and MGAT3 in PC. Furthermore, the effects of B3GNT3, FUT3, GCNT3 and MGAT3 were shown on proliferation, migration, EMT and stem cell markers in CD18 cell line. Talniflumate, GCNT3 inhibitor, reduced colony formation and migration in T3M4 and CD18 cells. Moreover, we found that loss of GCNT3 suppresses PC progression and metastasis by downregulating cell cycle genes and β-catenin/MUC4 axis. For GCNT3, proteomics revealed downregulation of MUC5AC, MUC1, MUC5B including many other proteins.

CONCLUSIONS

Collectively, we demonstrate a critical role of O- and N-linked glycoTs in PC progression and delineate the mechanism encompassing the role of GCNT3 in PC.

Abstract 4684: Afatinib targets glioblastoma stem cells by inhibiting EGFRVIII-cMet co-activation

Background

Glioblastoma (GBM) is the aggressive primary brain tumor with a median survival rate of 14.6 months. Currently, first-line treatment includes surgical resection, chemoradiation, and adjuvant chemotherapy with temozolomide (TMZ). However, GBM recurs most often within 6.9 months. Most of the targeted therapies failed in GBM, possibly due to the co-activation of the receptor tyrosine kinases (RTKs). Genetic analysis on GBM tumor revealed that RTKs are dysregulated, with epidermal growth factor receptor (EGFR) representing 57.4% of the deleted/mutated GBM, about 30 - 40% of GBM patients with EGFR amplification carry an oncogenic gene rearrangement EGFR variant III (EGFRvIII) which is constitutively active. In addition, EGFRvIII co-activates cMET RTKs thereby enriches GBM cancer stem like cells (CSCs). CSCs are relatively radio- and chemo- resistant and play a pivotal role in tumor recurrence/progression. We hypothesize that afatinib and TMZ combination would inhibit EGFRvIII co-activation and tumor progression in GBM model.

Methods

GBM cell lines U87MG, U87MG transfected with EGFRvIII (U87 EGFRvIII) and SP/CSC isolated from U87 EGFRvIII cells were treated with afatinib, TMZ alone or in combination and analyzed. The in vivo efficacy of these drugs were also analyzed on U87 EGFRvIII orthograft mouse model.

Results

We observed significantly higher proportion of CSCs in U87 EGFRvIII cells compared to U87MG cells (p = 0.03). While afatinib decreased the percentage of CSCs in both U87MG and U87 EGFRvIII cells (p = 0.02), TMZ only decreased CSC population in U87MG cells. However, combination of afatinib with TMZ significantly decreased the CSCs in both U87MG and U87 EGFRvIII cells (p = 0.02). Our clonogenic (tumorsphere) assay revealed significantly more tumorspheres (p=0.01) formed by U87 EGFRvIII CSCs cells than U87MG CSCs. In addition, we also observed that TMZ significantly decreased the self-renewal properties of U87 CSCs compared to U87 EGFRvIII CSCs. Furthermore, afatinib alone or in combination with TMZ significantly abolished the tumorsphere formation by U87 EGFRvIII CSCs. The underlying mechanism revealed inhibition of cMET RTK co-activation by EGFRvIII using afatinib. Our in vivo studies using U87 EGFRvIII orthograft model revealed significant tumor growth inhibition by afatinib and TMZ combination compared to control and either drug alone.

Conclusion

Our results strongly support the efficacy of afatinib and TMZ combination in inhibiting EGFRvIII-cMET signaling mediated GBM stemness and prevention of tumor progression. This treatment should be tested in EGFR amplified/mutated GBM patients.

Note: This abstract was not presented at the meeting.

Citation Format: Raghupathy Vengoji, Muzafar A. Macha, Ramakrishna Nimmakayala, Satyanarayana Rachagani, Kavita Mallya, Maneesh Jain, Moorthy P. Ponnusamy, Surinder K. Batra, Nicole Shonka. Afatinib targets glioblastoma stem cells by inhibiting EGFRVIII-cMet co-activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4684.

Abstract 672: Targeting metabolic pathways to radiosensitize pancreatic cancer

Background: Pancreatic ductal adenocarcinoma (PDAC) is the third leading cause of cancer related mortality killing 117 PC patients every day in the United States. The efficacy of systemic chemotherapy and radiotherapy (RT) is tempered by the acquired and innate therapeutic resistance resulting in limited survival benefits to PDAC patients. Our bioinformatics and high throughput database analysis revealed that cholesterol biosynthesis (CBS) pathway is involved in radioresistance (RR) of PC patients. In addition, our previous studies suggested the involvement of FDPS, a CBS pathway enzyme, in imparting radioresistance to PC cells. Here, we tested the utility of Zoledronic acid (ZOL), a specific inhibitor of FDPS, in radiosensitization (RS) of PC cells in vitro and in vivo and investigated the underlying RS mechanisms. Material and Methods: RR PC cell lines (CD18/HPAF and Capan-1) were developed using fractionated irradiation (a total of 20 Gray) and validated using functional assays. RT-PCR and western blotting analysis were performed to determine the expression of CBS pathway associated transcripts and proteins. Stable CRISPR-Cas9 mediated knockout of FDPS in PC cells was developed to examine its role in PC radio sensitivity. Feasibility of pharmacologically inhibiting FDPS in in vitro and in vivo was tested using zoledronic acid (ZOL). Effect of ZOL on FDPS activity was studied by measuring intracellular cholesterol and by observing its inhibition on protein prenylation. Radiosenstization effects of ZOL on PC cells was analyzed using in vitro (FACS, cell cycle and clonogenic survival assay) and in vivo (orthotopic model) assays. Histological and immunohistochemistry analysis were performed to determine the levels of DNA damage markers on PC cells and pancreatic xenograft tissues. Results: Persistent exposure of PC cells to RT (20 Gy) resulted in altered cellular morphology, G2/M arrest and enriched side population accompanied by increased levels of FDPS and cell cycle regulatory proteins. Knockout of FDPS in PC cells enhanced radio-sensitivity. Pharmacological inhibition of FDPS in conjunction with radiation resulted in reduced number of colonies, increased apoptosis and abrogated radiation induced G2/M arrest. ZOL pre-treatment resulted in inhibition of prenylation of CDC42 and RAC1 GTPases and decreased accumulation of intracellular cholesterol. The combined therapy of ZOL and radiation resulted in significant reduction in tumor growth and metastasis as compared to ZOL and radiation alone treatment. Finally, we observed marked reduction in DNA repair proteins such as RAD50 and phosphorylation of P95 in cell lines knockout for FDPS/treated with ZOL and/or RT and xenograft tissues excised from single and combination treatment regimens. Conclusion: FDPS inhibition radiosensitizes PC cells by inducing G2/M cell cycle arrest and by abrogating radiation induced DNA repair mechanism thereby resulting in enhanced apoptosis.

Citation Format: Parthasarathy Seshacharyulu, Ramakrishna Nimmakayala, Satyanarayana Rachagani, Shuo Wang, Sicong Li, Geoffrey Talmon, Sukhwinder Kaur, Moorthy P. Ponnusamy, Maneesh Jain, Chi Lin, Surinder K. Batra. Targeting metabolic pathways to radiosensitize pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 672.

MicroRNA regulation of K-Ras in pancreatic cancer and opportunities for therapeutic intervention

The Ras family of GTPases is involved in cell proliferation, cell survival, and angiogenesis. It is upregulated in several cancers, including pancreatic cancer (PC) and leads to uncontrolled growth and aggressiveness. PC is well known to be a lethal disease with poor prognosis, plagued by limited therapeutic modalities. MicroRNAs (miRNAs), which are short non-coding RNA molecules, have recently emerged as regulators of signaling networks and have shown potential to target pathway components for therapeutic use in several malignancies. K-Ras mutations are widespread in PC cases (90%), with mutations detectable as early as pancreatic intraepithelial neoplasias and in later metastatic stages alike; therefore, these mutations in K-Ras are obvious drivers and potential targets for PC therapy. Several K-Ras targeting miRNAs have lately been discovered, and many of them have shown promise in combating pancreatic tumor growth in vitro and in mouse models. However, the field of miRNA therapy is still in its infancy, and miRNA mimics or anti-miRNA oligonucleotides that target Ras pathway have thus far not been evaluated in PC patients. In this review, we summarize the role of several miRNAs that regulate oncogenic K-Ras signaling in PC, with their prospective roles as therapeutic agents for targeting K-Ras pathway.

Abstract 2490: Smoking enriches cancer stem cell population and activates Sox9 through NF-kB signaling in pancreatic ductal adenocarcinoma

Introduction: Recent studies have demonstrated a clear association between smoking and the incidence of pancreatic ductal adenocarcinoma (PDAC); however, the effect of cigarette smoke in the activation of stem cell (SC) or cancer stem cell (CSC) genes and their involvement in the initiation and progression of PDAC have not yet been studied. It is well known that CSCs are responsible for the drug resistance and aggressiveness of the disease including PDAC. In this study, we investigated the effects of smoking on enrichment of SC/CSCs in pancreatic normal and ductal adenocarcinoma cells, and we also examined whether smoking can activate NF-kB signaling, which is in part leads to enrichment of CSC and induction of CSC markers in PDAC.

Methods: Cigarette smoke extract (CSE) was prepared, and HPNE (Human pancreatic nestin positive cells) and Capan-1 pancreatic cancer (PC) cells were treated with CSE for up to ∼15 weeks. Side population (SP) were analyzed by Hoechst staining using Flow-cytomer, and various CSC markers such as PD2 (a stem cell maintenance marker), CD44, ALDH-1, SOX-9 (a multipotent SC marker) and Oct-3/4 (a pluripotent marker), and NF-kB signaling molecules were analyzed by western blotting. ALDH1+ cells, CD44+CD24+ CSCs and G0/G1 phase low cycling quiescent cells were analyzed by flow cytometer. An in-vitro sphere culture was also performed to further confirm the smoke induced CSC properties. Smoke exposed pancreatic tissues excised from unfloxed littermate control (LSL-K-Ras G12D) pancreatic tissue sections were immunostained for SOX-9 using immunohistochemistry (IHC), and for SOX9 and CD44 using immunofluorescence.

Results: Our results showed increased SC/CSCs and more number of spheres by CSE treated cells as compared to their untreated controls and displayed elevated protein expressions of SC/CSC markers. We also observed an elevated CD44+CD24+ CSCs, increased ALDH1+ cells and increased G0/G1 low cycling quiescent cell population in CSE treated cells as compared to untreated controls. In addition, increased immunohistochemical staining for SOX9 and increased immunofluorescent signal for SOX-9 and CD44 were observed in smoke exposed animal tissues indicating that smoking may transform SOX-9+ multipotent SCs into SOX9+CD44+ CSCs. We also analyzed the expression levels of NF-kB signaling molecules in CSE treated HPNE and Capan-1 cells. As compared to their untreated controls, CSE treated cells showed elevated protein expression levels of phospho AKT, phospho RelA (SOX-9 promoter binding subunit of NF-kB complex) and phospho IKKα (a kinase that phosphorylates IKBα, an inhibitor of RelA) suggesting that smoking activates NF-kB signaling.

Conclusion: Our results illustrate that smoking enriches SC/CSCs populations in normal pancreatic cells as well as in pancreatic cancer cells, and activates SOX9 through NF-kB signaling in PDAC.

Citation Format: Ramakrishna Nimmakayala, Parthasarathy Seshacharyulu, Seema Chugh, Imayavaramban Lakshmanan, Satyanarayana Rachagani, Surinder K Batra, Moorthy P Ponnusamy. Smoking enriches cancer stem cell population and activates Sox9 through NF-kB signaling in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2490.