The tumor suppressor gene ARHI regulates autophagy and tumor dormancy in human ovarian cancer cells.
The role of autophagy in oncogenesis remains ambiguous, and mechanisms that induce autophagy and regulate its outcome in human cancers are poorly understood. The maternally imprinted Ras-related tumor suppressor gene aplasia Ras homolog member I (ARHI; also known as DIRAS3) is downregulated in more than 60% of ovarian cancers, and here we show that re-expression of ARHI in multiple human ovarian cancer cell lines induces autophagy by blocking PI3K signaling and inhibiting mammalian target of rapamycin (mTOR), upregulating ATG4, and colocalizing with cleaved microtubule-associated protein light chain 3 (LC3) in autophagosomes. Furthermore, ARHI is required for spontaneous and rapamycin-induced autophagy in normal and malignant cells. Although ARHI re-expression led to autophagic cell death when SKOv3 ovarian cancer cells were grown in culture, it enabled the cells to remain dormant when they were grown in mice as xenografts. When ARHI levels were reduced in dormant cells, xenografts grew rapidly. However, inhibition of ARHI-induced autophagy with chloroquine dramatically reduced regrowth of xenografted tumors upon reduction of ARHI levels, suggesting that autophagy contributed to the survival of dormant cells. Further analysis revealed that autophagic cell death was reduced when cultured human ovarian cancer cells in which ARHI had been re-expressed were treated with growth factors (IGF-1, M-CSF), angiogenic factors (VEGF, IL-8), and matrix proteins found in xenografts. Thus, ARHI can induce autophagic cell death, but can also promote tumor dormancy in the presence of factors that promote survival in the cancer microenvironment.
Lu
Zhen
Z
Department of Experimental Therapeutics, University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA.
Luo
Robert Z
RZ
Lu
Yiling
Y
Zhang
Xuhui
X
Yu
Qinghua
Q
Khare
Shilpi
S
Kondo
Seiji
S
Kondo
Yasuko
Y
Yu
Yinhua
Y
Mills
Gordon B
GB
Liao
Warren S-L
WS
Bast
Robert C
RC
D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D018501:Antirheumatic Agents / Q000494:pharmacology; D001343:Autophagy / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002738:Chloroquine / Q000494:pharmacology; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D005260:Female; D018392:Genomic Imprinting / Q000187:drug effects / Q000235:genetics; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009368:Neoplasm Transplantation; D010051:Ovarian Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010588:Phagosomes / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases; D014183:Transplantation, Heterologous; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D000903:Antibiotics, Antineoplastic; D018501:Antirheumatic Agents; D002738:Chloroquine; D003546:Cysteine Endopeptidases; D036341:Intercellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D025521:Tumor Suppressor Proteins; D020741:rho GTP-Binding Proteins; C117386:DIRAS3 protein, human; C477012:MAP1LC3A protein, human; C546842:MTOR protein, human; C546843:mTOR protein, mouse