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Dormancy of cancer cells with suppression of AKT activity contributes to survival in chronic hypoxia.

Endo H, Okuyama H, Ohue M, Inoue M - PLoS ONE (2014)

Bottom Line: ATP turnover, an indicator of energy demand, was markedly decreased and accompanied by reduced AKT phosphorylation.Forced activation of AKT resulted in increased ATP turnover and massive cell death in vitro and a decreased number of dormant cells in vivo.Primary colorectal cancer cells in dormancy were resistant to chemotherapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.

ABSTRACT
A hypoxic microenvironment in tumors has been recognized as a cause of malignancy or resistance to various cancer therapies. In contrast to recent progress in understanding the acute response of cancer cells to hypoxia, the characteristics of tumor cells in chronic hypoxia remain elusive. We have identified a pancreatic cancer cell line, AsPC-1, that is exceptionally able to survive for weeks under 1% oxygen conditions while most tested cancer cell lines die after only some days under these conditions. In chronic hypoxia, AsPC-1 cells entered a state of dormancy characterized by no proliferation, no death, and metabolic suppression. They reversibly switched to active status after being placed again in optimal culture conditions. ATP turnover, an indicator of energy demand, was markedly decreased and accompanied by reduced AKT phosphorylation. Forced activation of AKT resulted in increased ATP turnover and massive cell death in vitro and a decreased number of dormant cells in vivo. In contrast to most cancer cell lines, primary-cultured colorectal cancer cells easily entered the dormant status with AKT suppression under hypoxia combined with growth factor-depleted conditions. Primary colorectal cancer cells in dormancy were resistant to chemotherapy. Thus, the ability to survive in a deteriorated microenvironment by entering into dormancy under chronic hypoxia might be a common property among cancer cells. Targeting the regulatory mechanism inducing this dormant status could provide a new strategy for treating cancer.

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Related in: MedlinePlus

Downregulation of AKT phosphorylation is necessary for induction of dormant status in primary colorectal cancer.A) CTOS growth was measured by size relative to day 0. C45 CTOS samples were cultured in medium with (GF+) or without (GF−) growth factors. B) Representative images of C45 CTOS cultured in indicated conditions. Scale bar  = 100 µm. C) Regrowth of CTOS in dormant status after re-oxygenation and exposure to growth factor–containing medium. D) Immunohistochemistry of C45 CTOS cultured in indicated conditions for 1 day. TUNEL staining was at day 14. Scale bar  = 50 µm. E) Immunoblot of AKT/mTORC1 signaling and HIF-1α in C45 CTOS cultured in indicated conditions.
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pone-0098858-g005: Downregulation of AKT phosphorylation is necessary for induction of dormant status in primary colorectal cancer.A) CTOS growth was measured by size relative to day 0. C45 CTOS samples were cultured in medium with (GF+) or without (GF−) growth factors. B) Representative images of C45 CTOS cultured in indicated conditions. Scale bar  = 100 µm. C) Regrowth of CTOS in dormant status after re-oxygenation and exposure to growth factor–containing medium. D) Immunohistochemistry of C45 CTOS cultured in indicated conditions for 1 day. TUNEL staining was at day 14. Scale bar  = 50 µm. E) Immunoblot of AKT/mTORC1 signaling and HIF-1α in C45 CTOS cultured in indicated conditions.

Mentions: Next, we examined whether induction of dormant status under chronic hypoxia was also observed in primary cultured cancer cells. We recently established a novel primary culture system, CTOS (cancer tissue–originated spheroid), in colorectal, lung, and urothelial cancer [28]–[30]. We prepared CTOS samples from colorectal cancer patients and cultured them in vitro (Figure 5A and B). CTOS growth was completely inhibited under a combination of hypoxia and growth factor–deprived conditions, although hypoxia alone was not sufficient to eliminate the growth. We tested CTOS from three colorectal cancer patients, and all samples re-grew well immediately after re-exposure to oxygen and growth factor–containing medium (Figure 5C). Thus, the induction of dormancy was not restricted to AsPC-1 cells but also was observed in primary cancer cells.


Dormancy of cancer cells with suppression of AKT activity contributes to survival in chronic hypoxia.

Endo H, Okuyama H, Ohue M, Inoue M - PLoS ONE (2014)

Downregulation of AKT phosphorylation is necessary for induction of dormant status in primary colorectal cancer.A) CTOS growth was measured by size relative to day 0. C45 CTOS samples were cultured in medium with (GF+) or without (GF−) growth factors. B) Representative images of C45 CTOS cultured in indicated conditions. Scale bar  = 100 µm. C) Regrowth of CTOS in dormant status after re-oxygenation and exposure to growth factor–containing medium. D) Immunohistochemistry of C45 CTOS cultured in indicated conditions for 1 day. TUNEL staining was at day 14. Scale bar  = 50 µm. E) Immunoblot of AKT/mTORC1 signaling and HIF-1α in C45 CTOS cultured in indicated conditions.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4048292&req=5

pone-0098858-g005: Downregulation of AKT phosphorylation is necessary for induction of dormant status in primary colorectal cancer.A) CTOS growth was measured by size relative to day 0. C45 CTOS samples were cultured in medium with (GF+) or without (GF−) growth factors. B) Representative images of C45 CTOS cultured in indicated conditions. Scale bar  = 100 µm. C) Regrowth of CTOS in dormant status after re-oxygenation and exposure to growth factor–containing medium. D) Immunohistochemistry of C45 CTOS cultured in indicated conditions for 1 day. TUNEL staining was at day 14. Scale bar  = 50 µm. E) Immunoblot of AKT/mTORC1 signaling and HIF-1α in C45 CTOS cultured in indicated conditions.
Mentions: Next, we examined whether induction of dormant status under chronic hypoxia was also observed in primary cultured cancer cells. We recently established a novel primary culture system, CTOS (cancer tissue–originated spheroid), in colorectal, lung, and urothelial cancer [28]–[30]. We prepared CTOS samples from colorectal cancer patients and cultured them in vitro (Figure 5A and B). CTOS growth was completely inhibited under a combination of hypoxia and growth factor–deprived conditions, although hypoxia alone was not sufficient to eliminate the growth. We tested CTOS from three colorectal cancer patients, and all samples re-grew well immediately after re-exposure to oxygen and growth factor–containing medium (Figure 5C). Thus, the induction of dormancy was not restricted to AsPC-1 cells but also was observed in primary cancer cells.

Bottom Line: ATP turnover, an indicator of energy demand, was markedly decreased and accompanied by reduced AKT phosphorylation.Forced activation of AKT resulted in increased ATP turnover and massive cell death in vitro and a decreased number of dormant cells in vivo.Primary colorectal cancer cells in dormancy were resistant to chemotherapy.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Osaka Medical Center for Cancer and Cardiovascular Diseases, Osaka, Japan.

ABSTRACT
A hypoxic microenvironment in tumors has been recognized as a cause of malignancy or resistance to various cancer therapies. In contrast to recent progress in understanding the acute response of cancer cells to hypoxia, the characteristics of tumor cells in chronic hypoxia remain elusive. We have identified a pancreatic cancer cell line, AsPC-1, that is exceptionally able to survive for weeks under 1% oxygen conditions while most tested cancer cell lines die after only some days under these conditions. In chronic hypoxia, AsPC-1 cells entered a state of dormancy characterized by no proliferation, no death, and metabolic suppression. They reversibly switched to active status after being placed again in optimal culture conditions. ATP turnover, an indicator of energy demand, was markedly decreased and accompanied by reduced AKT phosphorylation. Forced activation of AKT resulted in increased ATP turnover and massive cell death in vitro and a decreased number of dormant cells in vivo. In contrast to most cancer cell lines, primary-cultured colorectal cancer cells easily entered the dormant status with AKT suppression under hypoxia combined with growth factor-depleted conditions. Primary colorectal cancer cells in dormancy were resistant to chemotherapy. Thus, the ability to survive in a deteriorated microenvironment by entering into dormancy under chronic hypoxia might be a common property among cancer cells. Targeting the regulatory mechanism inducing this dormant status could provide a new strategy for treating cancer.

Show MeSH
Related in: MedlinePlus