SPARC dependent collagen deposition and gemcitabine delivery in a genetically engineered mouse model of pancreas cancer

Abstract

Background: Pancreatic ductal adenocarcinoma (PDAC) is characterised by extensive matrix deposition that has been implicated in impaired drug delivery and therapeutic resistance. Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that regulates collagen deposition and is highly upregulated in the activated stroma subtype with poor prognosis in PDAC patients. Methods: Kras G12D ;p48-Cre;SPARC −/− (KC-SPARC −/−) and Kras G12D ;p48-Cre;SPARC WT (KC-SPARC WT) were generated and analysed at different stages of carcinogenesis by histological grading, immunohistochemistry for epithelial and stromal markers, survival and preclinical analysis. Pharmacokinetic and pharmacodynamic studies were conducted by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunohistochemistry following gemcitabine treatment (100 mg/kg) in vivo. Findings: Global genetic ablation of SPARC in a Kras G12D driven mouse model resulted in significantly reduced overall and mature collagen deposition around early and advanced pancreatic intraepithelial neoplasia (PanIN) lesions and in invasive PDAC (p < .001). However, detailed pathological scoring and molecular analysis showed no effects on PanIN to PDAC progression, vessel density (CD31), tumour incidence, grading or metastatic frequency. Despite comparable tumour kinetics, ablation of SPARC resulted in a significantly shortened survival in KC-SPARC −/− mice (280 days versus 485 days, p < .03, log-rank-test). Using LC-MS/MS, we show that SPARC dependent collagen deposition does not affect intratumoural gemcitabine accumulation or immediate therapeutic response in tumour bearing KC-SPARC WT and KC-SPARC −/− mice. Interpretation: Global SPARC ablation reduces the collagen-rich microenvironment in murine PDAC. Moreover, global SPARC depletion did not affect tumour growth kinetics, grading or metastatic frequency. Notably, the dense-collagen matrix did not restrict access of gemcitabine to the tumour. These findings may have direct translational implications in clinical trial design.

Ferroptotic damage promotes pancreatic tumorigenesis through a TMEM173/STING-dependent DNA sensor pathway

“…We did not exclude samples or animals. No statistical methods were used to predetermine sample sizes, but our sample sizes ( n = 10 mice/group) for survival analysis are similar to those generally employed in the field 53 . All treatments were performed by technicians who were not blind, but not involved in sample measurement.…”

“…We did not exclude samples or animals. No statistical methods were used to predetermine sample sizes, but our sample sizes are similar to those generally employed in the field 53 .…”

Secreted Protein Acidic and Rich in Cysteine as A Regeneration Factor: Beyond the Tissue Repair

“…Furthermore, an improved muscular function (including during exercise) would lead to reducing the accumulation of the lactic acid and, therefore, better control of the pH, which both impacts muscle fatigue [ 71 , 72 ] and represents another important factor for different cellular functions [ 73 ], including those related to regeneration [ 74 , 75 ]. In addition, ageing-induced collagen loss [ 76 ] would be counteracted via the roles of SPARC in collagen properties [ 77 , 78 , 79 , 80 ]. Moreover, many SPARC effects counteract ageing impacts.…”

Depletion of Macrophages Improves Therapeutic Response to Gemcitabine in Murine Pancreas Cancer

“…For pharmacokinetic studies, KC mice were treated with gemcitabine (100 mg/kg body weight) once. Biopsies (n = 5) from tumor-bearing KC mice were partly overlapping with the KC-WT control group that was recently published from our group [4]. All tissues were harvested 2 h after the last gemcitabine dose for further analysis as previously described [21].…”

“…It is undisputed that the tumor microenvironment (TME) closely interacts with surrounding tumor cells via direct physical interaction and multiple signaling cues, promoting tumor progression and therapeutic resistance in PDAC [2]. However, recent evidence points towards a more complex role of distinct components of the TME, with both tumor-restraining as well as tumor-promoting properties [3][4][5][6]. Indeed, several large clinical trials using anti-stromal agents (e.g., hyaluronidase PEGPH20, sonic hedgehog inhibitors, matrix metalloproteinase (MMP) inhibitors) have recently failed to achieve meaningful clinical response rates in PDA patients, and so far, no anti-stromal therapies have been approved [7].…”