Autophagy regulates keratin 8 homeostasis in mammary epithelial cells and in breast tumors.
Autophagy is activated in response to cellular stressors and mediates lysosomal degradation and recycling of cytoplasmic material and organelles as a temporary cell survival mechanism. Defective autophagy is implicated in human pathology, as disruption of protein and organelle homeostasis enables disease-promoting mechanisms such as toxic protein aggregation, oxidative stress, genomic damage, and inflammation. We previously showed that autophagy-defective immortalized mouse mammary epithelial cells are susceptible to metabolic stress, DNA damage, and genomic instability. We now report that autophagy deficiency is associated with endoplasmic reticulum (ER) and oxidative stress, and with deregulation of p62-mediated keratin homeostasis in mammary cells, allograft tumors, and mammary tissues from genetically engineered mice. In human breast tumors, high phospho(Ser73)-K8 levels are inversely correlated with Beclin 1 expression. Thus, autophagy preserves cellular fitness by limiting ER and oxidative stress, a function potentially important in autophagy-mediated suppression of mammary tumorigenesis. Furthermore, autophagy regulates keratin homeostasis in the mammary gland via a p62-dependent mechanism. High phospho(Ser73)-K8 expression may be a marker of autophagy functional status in breast tumors and, as such, could have therapeutic implications for breast cancer patients.
Cancer Institute of New Jersey, 195 Little Albany Street, New Brunswick, NJ 08903, USA.
Sameera
S
Kongara
Olga
O
Kravchuk
Irina
I
Teplova
Fred
F
Lozy
Jennifer
J
Schulte
Dirk
D
Moore
Nicola
N
Barnard
Carola A
CA
Neumann
Eileen
E
White
Vassiliki
V
Karantza
D000818:Animals; D001343:Autophagy / Q000235:genetics; D020134:Catalytic Domain / Q000235:genetics; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D006706:Homeostasis / Q000235:genetics; D006801:Humans; D053533:Keratin-8 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D051379:Mice; D018345:Mice, Knockout; D008819:Mice, Nude; D008822:Mice, Transgenic; D018384:Oxidative Stress / Q000235:genetics; D010768:Phosphoserine / Q000378:metabolism
D053533:Keratin-8; C486595:Krt8 protein, mouse; D010768:Phosphoserine