Hypoxic activation of the unfolded protein response (UPR) induces expression of the metastasis-associated gene LAMP3.
OBJECTIVE
Tumour hypoxia contributes to failure of cancer treatment through its ability to protect against therapy and adversely influence tumour biology. In particular, several studies suggest that hypoxia promotes metastasis. Hypoxia-induced cellular changes are mediated by oxygen-sensitive signaling pathways that activate downstream transcription factors. We have investigated the induction and transcriptional regulation of a novel metastasis-associated gene, LAMP3 during hypoxia.


METHODS
Microarray, quantitative PCR, Western blot analysis and immunohistochemistry were used to investigate hypoxic regulation of LAMP3. The mechanism for LAMP3 induction was investigated using transient RNAi and stable shRNA targeting components of the hypoxic response. Endoplasmic reticulum stress inducing agents, including proteasome inhibitors were assessed for their ability to regulate LAMP3.


RESULTS
LAMP3 is strongly induced by hypoxia at both the mRNA and protein levels in a large panel of human tumour cell lines. Induction of LAMP3 occurs as a consequence of the activation of the PERK/eIF2alpha/ATF4 arm of the unfolded protein response (UPR) and is independent of HIF-1alpha. LAMP3 is expressed heterogeneously within the microenvironment of tumours, overexpressed in breast cancer, and increases in tumours treated with avastin.


CONCLUSIONS
These data identify LAMP3 as a novel hypoxia-inducible gene regulated by the UPR. LAMP3 is a new candidate biomarker of UPR activation by hypoxia in tumours and is a potential mediator of hypoxia-induced metastasis.
Mujcic
Hilda
H
Maastricht Radiation Oncology (MaastRO) Lab, Maastricht University, The Netherlands.
Rzymski
Tomasz
T
Rouschop
Kasper M A
KM
Koritzinsky
Marianne
M
Milani
Manuela
M
Harris
Adrian L
AL
Wouters
Bradly G
BG
D000818:Animals; D014408:Biomarkers, Tumor / Q000235:genetics*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D000860:Hypoxia / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D051907:Lysosomal Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D009362:Neoplasm Metastasis / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011336:Probability; D040081:Protein Array Analysis; D034741:RNA, Small Interfering / Q000032:analysis; D012016:Reference Values; D014162:Transfection; D014407:Tumor Cells, Cultured; D056811:Unfolded Protein Response / Q000235:genetics*; D059666:Lysosomal-Associated Membrane Protein 3
D014408:Biomarkers, Tumor; D051907:Lysosomal Membrane Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; C114233:LAMP3 protein, human; D059666:Lysosomal-Associated Membrane Protein 3