Role of Endothelin Axis in Pancreatic Tumor Microenvironment

Endothelins (ETs) are a family of three 21 amino-acid vasoactive peptides ET-1, ET-2 and ET-3 that mediate their effects via two G-protein couple receptors ETAR and ETBR which are expressed on various cell types. Apart from their physiological role in vasoconstriction, there is emerging evidence supporting the role of endothelin axis (ET-axis) in cancer. Due to the expression of ET receptors on various cell-types, ET-axis can exert pleotropic effects and contribute to various aspects of cancer pathobiology. Several studies have provided a fragmented picture of the diverse roles or ET-axis in various tumors. However, the comprehensive picture of the pathobiological role of this axis in any given cancer is poorly understood. Given that PC epitomizes the complexity of tumor microenvironment (TME), which is an active player in disease progression and therapy resistance, the overarching goal of this dissertation was to define the role of ET-axis in this lethal malignancy. Specifically, the dissertation was aimed at defining the expression pattern of ET axis in PC TME and elucidating the pathobiological significance of ET axis in PC. Immunohistochemistry (IHC) analysis of surgically resected tumor tissues from PC patients indicated expression of ECE-1, ET-1, ETAR and ETBR expression in both primary and metastatic lesions. In addition to tumor cells, ETAR and ETBR expression was observed on blood vessels (BV), stromal cells including stellate cells and infiltrating immune cells. The expression of ETAR and ETBR in various cellular compartments was also analyzed using marker for tumor cell (CK19), blood vessel (CD31), stellate cell (alpha SMA) and macrophages (CD68 and F4/80). Importantly, analysis of survival data showed ETBR positivity on BV is correlated with poor prognosis of the PC patients. Bioinformatics analysis of TCGA database revealed high positive correlation of the pro-fibrotic gene signatures with both ETAR and ETBR particularly Collagen I (Col1A2, Col3A1, Col5A2, Col6A3), Platelet derived growth factor receptor beta (PDGFRβ), Fibroblast activation protein (FAP), suggesting a pro-fibrotic role of ET axis in PC. In the second part of the dissertation, we studied the impact of ET-axis inhibition in autochthonous tumors that develop in genetically engineered mouse model (KPC). Treatment with dual ET receptor antagonist Bosentan induced cell death in the autochthonous tumors, decreased IHC signal for extracellular matrix proteins (α-SMA, Collagen I, Fibronectin and CTGF). Transcriptomic analysis using fibrosis gene array indicated anti-fibrogenic effects of Bosentan in KPC tumors. Further, treatment of murine pancreatic stellate cells (PSCs) and human cancer associated fibroblasts (CAFs) with recombinant ET-1 in vitro induced the expression of pro-fibrotic genes was abrogated by selective inhibition of ETAR (BQ123) and ETBR (BQ788) signaling with synergistic effects observed with dual receptor inhibition. Further, ET-1 stimulation induced a significant increase in the p-ERK and p-AKT in a time dependent manner and dual receptor antagonist Bosentan significantly attenuated the ET-1 mediated induction. Our study also demonstrates that targeting ETAR with a specific inhibitor BQ123 enhances perfusion selectively in the tumor and reduces hypoxia in xenograft PC tumors. The third part of the dissertation describes a possible involvement of ET axis in inflammation associated pancreatic tumor progression in presence if mutated KrasG12D. The expression of ET axis components initially is restricted to pancreatic acinar and islet cell compartment in physiological conditions. However, during inflammation or injury the acinar expression is abrogated and is seen in early pre-cancerous lesions and neoplastic cells. The reprogramming of acinar phenotype into early pre-neoplastic lesions indicates an essential role of ET axis in pancreatic acinar to ductal metaplasia. This trans-differentiation is followed by excessive accumulation of ECM proteins and inflammatory reaction in the pancreas, indicating further involvement of ET axis in influencing micro-environmental factors in initiation and progression of pancreatic cancer. The fourth part of the dissertation describes the generation of the mouse model aimed at delineating the role of ET-1 in PC progression. Genetically engineered mouse model of PC (K-rasG12D; Trp53R172H/+; Pdx-1-Cre) that harbors a Kras and p53 mutation in the pancreas were crossed with the ET-1 flox/flox mice. Taken together, studies in this dissertation demonstrate that ET axis plays a pleotropic role in the TME, and targeting ET axis can modulate the obstructive and immunosuppressive TME and make it potentially more amenable for chemotherapy and immunotherapy

The role of phospholipid as a solubility- and permeability-enhancing excipient for the improved delivery of the bioactive phytoconstituents of Bacopa monnieri

In an attempt to improve the solubility and permeability of Standardized Bacopa Extract (SBE), a complexation approach based on phospholipid was employed. A solvent evaporation method was used to prepare the SBE-phospholipid complex (Bacopa Naturosome, BN). The formulation and process variables were optimized using a central-composite design. The formation of BN was confirmed by photomicroscopy, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Powder X-ray Diffraction (PXRD). The saturation solubility, the in-vitro dissolution, and the ex-vivo permeability studies were used for the functional evaluation of the prepared complex. BN exhibited a significantly higher aqueous solubility compared to the pure SBE (20-fold), or the physical mixture of SBE and the phospholipid (13-fold). Similarly, the in-vitro dissolution revealed a significantly higher efficiency of the prepared complex (BN) in releasing the SBE (\u3e 97%) in comparison to the pure SCE (~ 42%), or the physical mixture (~ 47%). The ex-vivo permeation studies showed that the prepared BN significantly improved the permeation of SBE (\u3e 90%), compared to the pure SBE (~ 21%), or the physical mixture (~ 24%). Drug-phospholipid complexation may thus be a promising strategy for solubility enhancement of bioactive phytoconstituents

Emerging trends for radioimmunotherapy in solid tumors.

Due to its ability to target both known and occult lesions, radioimmunotherapy (RIT) is an attractive therapeutic modality for solid tumors. Poor tumor uptake and undesirable pharmacokinetics, however, have precluded the administration of radioimmunoconjugates at therapeutically relevant doses thereby limiting the clinical utility of RIT. In solid tumors, efficacy of RIT is further compromised by heterogeneities in blood flow, tumor stroma, expression of target antigens and radioresistance. As a result significant efforts have been invested toward developing strategies to overcome these impediments. Further, there is an emerging interest in exploiting short-range, high energy α-particle emitting radionuclides for the eradication of minimal residual and micrometastatic disease. As a result several modalities for localized therapy and models of minimal disease have been developed for preclinical evaluation. This review provides a brief update on the recent efforts toward improving the efficacy of RIT for solid tumors, and development of RIT strategies for minimal disease associated with solid tumors. Further, some of promising approaches to improve tumor targeting, which showed promise in the past, but have now been ignored are also discussed

Influence of Carrier (Polymer) Type and Drug-Carrier Ratio in the Development of Amorphous Dispersions for Solubility and Permeability Enhancement of Ritonavir

The influence of the ratio of Eudragit® L100-55 or Kolliphor® P188 on the solubility, dissolution, and permeability of ritonavir was studied with a goal of preparing solid dispersions (SDs) of ritonavir. SDs were formulated using solvent evaporation or lyophilization techniques, and evaluated for their physical-chemical properties. The dissolution and permeability assessments of the functionality of the SDs were carried out. The preliminary functional stability of these formulations was assessed at accelerated storage conditions for a period of six months. Ritonavir: Eudragit® L100-55 (RE, 1:3) SD showed a 36-fold higher ritonavir solubility compared to pure ritonavir. Similarly, ritonavir: Kolliphor® P188 (RP, 1:2) SD exhibited a 49-fold higher ritonavir solubility compared to pure ritonavir. Ritonavir dissolution from RE formulations increased with increasing ratios of Eudragit® L100-55, up to a ritonavir: carrier ratio of 1:3. The ritonavir dissolution from RP formulations was highest at ritonavir: Kolliphor® P188 ratio of 1:2. Dissolution efficiencies of these formulations were found to be in line with, and supported the dissolution results. The permeability of ritonavir across the biological membrane from the optimized formulations RE (1:3) and RP (1:2) were ~76 % and ~97 %, respectively; and were significantly higher compared to that of pure ritonavir (~20 %). A preliminary (six-month) stability study demonstrated the functional stability of prepared solid dispersions. The present study demonstrates that ritonavir solubility, dissolution, and permeability improvement can be achieved with a careful choice of the carrier polymer, and optimizing the amount of polymer in a SD formulation

Unbiased analysis of pancreatic cancer radiation resistance reveals cholesterol biosynthesis as a novel target for radiosensitisation.

BACKGROUND: Despite its promise as a highly useful therapy for pancreatic cancer (PC), the addition of external beam radiation therapy to PC treatment has shown varying success in clinical trials. Understanding PC radioresistance and discovery of methods to sensitise PC to radiation will increase patient survival and improve quality of life. In this study, we identified PC radioresistance-associated pathways using global, unbiased techniques. METHODS: Radioresistant cells were generated by sequential irradiation and recovery, and global genome cDNA microarray analysis was performed to identify differentially expressed genes in radiosensitive and radioresistant cells. Ingenuity pathway analysis was performed to discover cellular pathways and functions associated with differential radioresponse and identify potential small-molecule inhibitors for radiosensitisation. The expression of FDPS, one of the most differentially expressed genes, was determined in human PC tissues by IHC and the impact of its pharmacological inhibition with zoledronic acid (ZOL, Zometa) on radiosensitivity was determined by colony-forming assays. The radiosensitising effect of Zol in vivo was determined using allograft transplantation mouse model. RESULTS: Microarray analysis indicated that 11 genes (FDPS, ACAT2, AG2, CLDN7, DHCR7, ELFN2, FASN, SC4MOL, SIX6, SLC12A2, and SQLE) were consistently associated with radioresistance in the cell lines, a majority of which are involved in cholesterol biosynthesis. We demonstrated that knockdown of farnesyl diphosphate synthase (FDPS), a branchpoint enzyme of the cholesterol synthesis pathway, radiosensitised PC cells. FDPS was significantly overexpressed in human PC tumour tissues compared with healthy pancreas samples. Also, pharmacologic inhibition of FDPS by ZOL radiosensitised PC cell lines, with a radiation enhancement ratio between 1.26 and 1.5. Further, ZOL treatment resulted in radiosensitisation of PC tumours in an allograft mouse model. CONCLUSIONS: Unbiased pathway analysis of radioresistance allowed for the discovery of novel pathways associated with resistance to ionising radiation in PC. Specifically, our analysis indicates the importance of the cholesterol synthesis pathway in PC radioresistance. Further, a novel radiosensitiser, ZOL, showed promising results and warrants further study into the universality of these findings in PC, as well as the true potential of this drug as a clinical radiosensitiser

Influence of carrier (polymer) type and drug-carrier ratio in the development of amorphous dispersions for solubility and permeability enhancement of ritonavir.

The influence of the ratio of Eudragit® L100-55 or Kolliphor® P188 on the solubility, dissolution, and permeability of ritonavir was studied with a goal of preparing solid dispersions (SDs) of ritonavir. SDs were formulated using solvent evaporation or lyophilization techniques, and evaluated for their physical-chemical properties. The dissolution and permeability assessments of the functionality of the SDs were carried out. The preliminary functional stability of these formulations was assessed at accelerated storage conditions for a period of six months. Ritonavir: Eudragit® L100-55 (RE, 1:3) SD showed a 36-fold higher solubility of compared with pure ritonavir. Similarly, ritonavir:Kolliphor® P188 (RP, 1:2) SD exhibited a 49-fold higher solubility of ritonavir compared to pure ritonavir. Ritonavir dissolution from RE formulations increased with increasing ratios of Eudragit® L100-55, upto a ritonavir:carrier ratio of 1:3. The ritonavir dissolution from RP formulations was highest at a ritonavir:Kolliphor® P188 ratio of 1:2. Dissolution efficiencies of these formulations were found to be in line with, and supporting the dissolution results. The permeability of ritonavir across the biological membrane from the optimized formulations RE (1:3) and RP (1:2) were ~76 % and ~97 %, respectively; and were significantly higher compared to that of pure ritonavir (~20 %). A preliminary (six-month) stability study demonstrated the functional stability of prepared solid dispersions. The present study demonstrates that a good solubility, dissolution, and permeability improvement of ritonavir can be achieved with a careful choice of the carrier polymer, and by optimizing the amount of the chosen polymer in an SD formulation

Influence of carrier (polymer) type and drug-carrier ratio in the development of amorphous dispersions for solubility and permeability enhancement of ritonavir.

The influence of the ratio of Eudragit® L100-55 or Kolliphor® P188 on the solubility, dissolution, and permeability of ritonavir was studied with a goal of preparing solid dispersions (SDs) of ritonavir. SDs were formulated using solvent evaporation or lyophilization techniques, and evaluated for their physical-chemical properties. The dissolution and permeability assessments of the functionality of the SDs were carried out. The preliminary functional stability of these formulations was assessed at accelerated storage conditions for a period of six months. Ritonavir: Eudragit® L100-55 (RE, 1:3) SD showed a 36-fold higher solubility of compared with pure ritonavir. Similarly, ritonavir:Kolliphor® P188 (RP, 1:2) SD exhibited a 49-fold higher solubility of ritonavir compared to pure ritonavir. Ritonavir dissolution from RE formulations increased with increasing ratios of Eudragit® L100-55, upto a ritonavir:carrier ratio of 1:3. The ritonavir dissolution from RP formulations was highest at a ritonavir:Kolliphor® P188 ratio of 1:2. Dissolution efficiencies of these formulations were found to be in line with, and supporting the dissolution results. The permeability of ritonavir across the biological membrane from the optimized formulations RE (1:3) and RP (1:2) were ~76 % and ~97 %, respectively; and were significantly higher compared to that of pure ritonavir (~20 %). A preliminary (six-month) stability study demonstrated the functional stability of prepared solid dispersions. The present study demonstrates that a good solubility, dissolution, and permeability improvement of ritonavir can be achieved with a careful choice of the carrier polymer, and by optimizing the amount of the chosen polymer in an SD formulation

The role of phospholipid as a solubility- and permeability-enhancing excipient for the improved delivery of the bioactive phytoconstituents of Bacopa monnieri

In an attempt to improve the solubility and permeability of Standardized Bacopa Extract (SBE), a complexation approach based on phospholipid was employed. A solvent evaporation method was used to prepare the SBE-phospholipid complex (Bacopa Naturosome, BN). The formulation and process variables were optimized using a central-composite design. The formation of BN was confirmed by photomicroscopy, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Powder X-ray Diffraction (PXRD). The saturation solubility, the in-vitro dissolution, and the ex-vivo permeability studies were used for the functional evaluation of the prepared complex. BN exhibited a significantly higher aqueous solubility compared to the pure SBE (20-fold), or the physical mixture of SBE and the phospholipid (13-fold). Similarly, the in-vitro dissolution revealed a significantly higher efficiency of the prepared complex (BN) in releasing the SBE (\u3e 97%) in comparison to the pure SCE (~ 42%), or the physical mixture (~ 47%). The ex-vivo permeation studies showed that the prepared BN significantly improved the permeation of SBE (\u3e 90%), compared to the pure SBE (~ 21%), or the physical mixture (~ 24%). Drug-phospholipid complexation may thus be a promising strategy for solubility enhancement of bioactive phytoconstituents

Oncogene-regulated release of extracellular vesicles

Oncogenes can alter metabolism by changing the balance between anabolic and catabolic processes. However, how oncogenes regulate tumor cell biomass remains poorly understood. Using isogenic MCF10A cells transformed with nine different oncogenes, we show that specific oncogenes reduce the biomass of cancer cells by promoting extracellular vesicle (EV) release. While MYC and AURKB elicited the highest number of EVs, each oncogene selectively altered the protein composition of released EVs. Likewise, oncogenes alter secreted miRNAs. MYC-overexpressing cells require ceramide, whereas AURKB requires ESCRT to release high levels of EVs. We identify an inverse relationship between MYC upregulation and activation of the RAS/MEK/ERK signaling pathway for regulating EV release in some tumor cells. Finally, lysosome genes and activity are downregulated in the context of MYC and AURKB, suggesting that cellular contents, instead of being degraded, were released via EVs. Thus, oncogene-mediated biomass regulation via differential EV release is a new metabolic phenotype