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Mechanistic contribution of ubiquitous 15-lipoxygenase-1 expression loss in cancer cells to terminal cell differentiation evasion.

ABSTRACT: Loss of terminal cell differentiation promotes tumorigenesis. 15-Lipoxygenase-1 (15-LOX-1) contributes to terminal cell differentiation in normal cells. The mechanistic significance of 15-LOX-1 expression loss in human cancers to terminal cell differentiation suppression is unknown. In a screen of 128 cancer cell lines representing more than 20 types of human cancer, we found that 15-LOX-1 mRNA expression levels were markedly lower than levels in terminally differentiated cells. Relative expression levels of 15-LOX-1 (relative to the level in terminally differentiated primary normal human-derived bronchial epithelial cells) were lower in 79% of the screened cancer cell lines than relative expression levels of p16 (INK4A), which promotes terminal cell differentiation and is considered one of the most commonly lost tumor suppressor genes in cancer cells. 15-LOX-1 was expressed during terminal differentiation in three-dimensional air-liquid interface cultures, and 15-LOX-1 expression and terminal differentiation occurred in immortalized nontransformed bronchial epithelial but not in lung cancer cell lines. 15-LOX-1 expression levels were lower in human tumors than in paired normal lung epithelia. Short hairpin RNA-mediated downregulation of 15-LOX-1 in Caco-2 cells blocked enterocyte-like differentiation, disrupted tight junction formation, and blocked E-cadherin and ZO-1 localization to the cell wall membrane. 15-LOX-1 episomal expression in Caco-2 and HT-29 colon cancer cells induced differentiation. Our findings indicate that 15-LOX-1 downregulation in cancer cells is an important mechanism for terminal cell differentiation dysregulation and support the potential therapeutic utility of 15-LOX-1 reexpression to inhibit tumorigenesis.

SUBMITTER: Moussalli MJ

PROVIDER: S-EPMC3232310 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Mechanistic contribution of ubiquitous 15-lipoxygenase-1 expression loss in cancer cells to terminal cell differentiation evasion.

Moussalli Micheline J MJ Wu Yuanqing Y Zuo Xiangsheng X Yang Xiu L XL Wistuba Ignacio Ivan II Raso Maria G MG Morris Jeffrey S JS Bowser Jessica L JL Minna John D JD Lotan Reuben R Shureiqi Imad I

Cancer prevention research (Philadelphia, Pa.) 20110831 12

Loss of terminal cell differentiation promotes tumorigenesis. 15-Lipoxygenase-1 (15-LOX-1) contributes to terminal cell differentiation in normal cells. The mechanistic significance of 15-LOX-1 expression loss in human cancers to terminal cell differentiation suppression is unknown. In a screen of 128 cancer cell lines representing more than 20 types of human cancer, we found that 15-LOX-1 mRNA expression levels were markedly lower than levels in terminally differentiated cells. Relative express ...[more]

PMID: 21881028

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Project description:15-Lipoxygenase 2 (15-LOX2), a human-specific lipid-peroxidizing enzyme, is mainly expressed in luminal compartment of the normal prostate and often decreased or lost in prostate cancer (PCa). Previous studies from our lab implicate 15-LOX2 as a functional tumor suppressor. To better understand the biological role of 15-LOX2 in vivo, we established prostate-specific 15-LOX2 transgenic mice using the ARR2PB promoter. Unexpectedly, 15-LOX2 expression resulted in age-dependent prostatic hyperplasia. Interestingly, transgenic expression of 15-LOX2sv-b, a splice variant that lacks the arachidonic acid metabolizing activity, also induced hyperplasia and enlargement of the prostate. Prostatic hyperplasia induced by both 15-LOX2 and 15-LOX2sv-b was associated with an increase in proliferative (i..e., Ki67+) and luminal cells but 15-LOX2-induced hyperplasia was also accompanied by a prominent increase in basal cells. Microarray analysis revealed distinct gene expression profiles that could help explain the prostate phenotypes. Strikingly, 15-LOX2 (but not 15-LOX2sv-b) transgenic prostate showed up-regulation of several well-known stem/progenitor cell molecules including Sca-1, Trop2, p63 and Psca. Prostatic hyperplasia caused by both 15-LOX2 and 15-LOX2sv-b did not progress to PCa over >5 years of observations. Mechanistically, hyperplastic prostate lobes (especially those of the 15-LOX2 mice) showed a dramatic increase in senescent cells revealed by increased SA-ßgal, HP1, and p27Kip1 staining. Collectively, our results suggest that 15-LOX2 expression in mouse prostate leads to hyperplasia that activates the senescence checkpoint, which may in turn function as a barrier to tumor development. RNA was isolated from combined prostatic lobes of 6 mice (to reduce inter-animal variation) from ~2.5 month old (young; y) 15-LOX2 (line fl26), 15-LOX2sv-b (line svb9), wild type (wt) and ~15 month old (old; o) wt mice and hybridized onto Agilent's whole mouse genome oligoarrays arrays (G4122A) in fl26y(vs)wty, svb9y(vs)wty and wto(vs)wty combinations. The hybridizations were carried out in duplicates using an independent set of samples (biological replicates).

Dataset Information

Mechanistic contribution of ubiquitous 15-lipoxygenase-1 expression loss in cancer cells to terminal cell differentiation evasion.

Publications

Mechanistic contribution of ubiquitous 15-lipoxygenase-1 expression loss in cancer cells to terminal cell differentiation evasion.

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