Format

Send to

Choose Destination
Mol Oncol. 2015 Jan;9(1):105-14. doi: 10.1016/j.molonc.2014.07.024. Epub 2014 Aug 7.

Dying tumor cells stimulate proliferation of living tumor cells via caspase-dependent protein kinase Cδ activation in pancreatic ductal adenocarcinoma.

Author information

1
The Comprehensive Cancer Center & Shanghai Key Laboratory for Pancreatic Diseases, Shanghai First People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 201620, China.
2
Experimental Research Center, Shanghai First People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 201620, China.
3
Shanghai-MOST Key Laboratory of Health and Disease Genomics, Chinese National Human Genome Center, Shanghai 201203, China.
4
The Department of Dermatology, Duke University Medical Center, Durham, NC 27710, USA. Electronic address: chuan.li@duke.edu.
5
The Comprehensive Cancer Center & Shanghai Key Laboratory for Pancreatic Diseases, Shanghai First People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 201620, China. Electronic address: qhuang2007@gmail.com.

Abstract

Pancreatic cancer is one of the most lethal human cancers, and radiotherapy is often implemented for locally advanced pancreatic ductal adenocarcinoma. Tumor cell repopulation is a major challenge in treating cancers after radiotherapy. In order to address the problem of tumor repopulation, our previous studies have demonstrated that dying cells stimulate the proliferation of living tumor cells after radiotherapy. In particular, dying cells undergoing apoptosis also activate survival or proliferation signals and release growth factors to surrounding living cells. In the present study, we used an in vitro model to examine the possible mechanisms for dying cell stimulated tumor repopulation in pancreatic cancer. In this model, a small number of living, luciferase-labeled pancreatic cancer cells (reporter) were seeded onto a layer of a much larger number of irradiated, unlabeled pancreatic cancer cells and the growth of the living cells was measured over time as a gage of tumor repopulation. Our results indicate that irradiated, dying Panc1 feeder cells significantly stimulated the proliferation of living Panc1 reporter cells. Importantly, we identified that the percentage of apoptotic cells and the cleavage of caspases 3 and 7 and protein kinase Cδ (PKCδ) were increased in irradiated Panc1 cells. We presumed that caspases 3 and 7 and PKCδ as integral mediators in the process of dying pancreatic cancer cell stimulation of living tumor cell growth. In order to demonstrate the importance of caspases 3, 7 and PKCδ, we introduced dominant-negative mutants of caspase 3 (DN_C3), caspase 7 (DN_C7), or PKCδ (DN_PKCδ) into Panc1 cells using lentiviral vectors. The stably transduced Panc1 cells were irradiated and used as feeders and we found a significant decrease in the growth of living Panc1 reporter cells when compared with irradiated wild-type Panc1 cells as feeders. Moreover, the role of PKCδ in the growth stimulation of living tumor cells was further confirmed using a pan PKC inhibitor GF109203x and a specific PKCδ inhibitor, rottlerin. Additionally, we found significantly increased phosphorylation of Akt, p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase/stress-activated protein kinase (JNK1/2) in the irradiated Panc1 cells. Mechanistically, PKCδ cleavage was attenuated in both DN_C3 and DN_C7 transduced Panc1 cells, and both Akt and p38 MAPK phosphorylation were attenuated in DN_PKCδ transduced Panc1 cells following radiation. Thus, this report suggests a novel finding that cellular signaling caspase 3/7-PKCδ-Akt/p38 MAPK is crucial to the repopulation in Panc1 cells after radiotherapy.

KEYWORDS:

Akt/MAPK; Apoptosis; Caspase; PKCδ; Pancreatic cancer; Repopulation

PMID:
25156550
PMCID:
PMC4528398
DOI:
10.1016/j.molonc.2014.07.024
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Wiley Icon for PubMed Central
Loading ...
Support Center