JNK and PTEN cooperatively control the development of invasive adenocarcinoma of the prostate

Abstract

The c-Jun NH(2)-terminal kinase (JNK) signal transduction pathway is implicated in cancer, but the role of JNK in tumorigenesis is poorly understood. Here, we demonstrate that the JNK signaling pathway reduces the development of invasive adenocarcinoma in the phosphatase and tensin homolog (Pten) conditional deletion model of prostate cancer. Mice with JNK deficiency in the prostate epithelium (ΔJnk ΔPten mice) develop androgen-independent metastatic prostate cancer more rapidly than control (ΔPten) mice. Similarly, prevention of JNK activation in the prostate epithelium (ΔMkk4 ΔMkk7 ΔPten mice) causes rapid development of invasive adenocarcinoma. We found that JNK signaling defects cause an androgen-independent expansion of the immature progenitor cell population in the primary tumor. The JNK-deficient progenitor cells display increased proliferation and tumorigenic potential compared with progenitor cells from control prostate tumors. These data demonstrate that the JNK and PTEN signaling pathways can cooperate to regulate the progression of prostate neoplasia to invasive adenocarcinoma.

Fig. 1.

Loss of JNK cooperates with Pten deficiency to promote prostate cancer. (A) Genomic DNA isolated from the anterior prostate gland of ΔPten ΔJnk mice (Cre⁺ and Cre⁻) was examined by PCR using amplimers designed to detect the deleted Pten and Jnk alleles. (B) Representative prostate glands of WT, ΔJnk, ΔPten, and ΔPten ΔJnk mice (age 20 wk) are illustrated. (C) Kaplan–Meier analysis of the survival of WT, ΔJnk, ΔPten, and ΔPten ΔJnk mice. The lifespan of ΔPten ΔJnk mice was significantly shorter than ΔPten mice (P < 0.001). (D) Sections of the anterior prostate of ΔPten and ΔPten ΔJnk mice were stained with H&E or with antibodies to the androgen receptor (AR) or CK5. (E) Sections were stained with antibodies to pSer⁴⁷³ AKT or JNK1/2. (F) Sections were stained with antibodies to p63, CD44, or Ki67.

Fig. 2.

Effect of Mkk4 and Mkk7 gene ablation on ΔPten-dependent prostate cancer. (A and B) Representative images of prostate glands from ΔMkk4 ΔPten and ΔMkk7 ΔPten mice (age 20 wk) are illustrated. (C and D) Genomic DNA isolated from the prostate gland and tail of ΔMkk4 ΔPten (C) and ΔMkk7 ΔPten mice (D) were genotyped for Mkk4, Mkk7, and Pten alleles. (E) Representative H&E-stained tissue sections of the anterior prostate glands of ΔPten mice, ΔMkk4 ΔPten mice, and ΔMkk7 ΔPten mice (age 20 wk) are presented. (F–H) Representative image of a ΔMkk4 ΔMkk7 ΔPten prostate gland (20-wk-old mouse) is illustrated (F). Genomic DNA isolated from the prostate gland and tail of ΔMkk4 ΔMkk7 ΔPten mice were genotyped for Mkk4, Mkk7, and Pten alleles (G). A representative H&E-stained tissue section prepared from the anterior prostate gland of a ΔMkk4 ΔMkk7 ΔPten mouse (20 wk old) is presented (H).

Fig. 3.

Loss of JNK promotes prostate tumor metastasis. (A) Lumbar lymph nodes isolated from ΔJnk, ΔPten, and ΔPten ΔJnk mice (age, 20 wk) are illustrated. (B) Representative sections of ΔPten ΔJnk lumbar lymph nodes were stained with H&E or with antibodies to the androgen receptor (AR) or E-cadherin (ECad). (C) Representative sections of ΔPten ΔJnk lumbar lymph nodes were stained with antibodies to CK5 and CK8. The merged image includes the DNA stain DAPI.

Fig. 4.

Loss of JNK promotes proliferation of immature ΔPten prostate cells. (A) The cloning efficiency of Sca1⁺ cells isolated from ΔPten and ΔPten ΔJnk prostate tumors was measured at passage 2 in vitro. Equal numbers of Sca1⁺ cells were plated and the number of prostaspheres obtained after 14 d in culture was examined (mean ± SD; n = 3). Significant differences are indicated (*P < 0.05). (B) Sections of prostaspheres were stained for DNA (DAPI) and the stem cell markers p63 and nucleostemin (NS). (C and D) Sections of prostaspheres were stained with H&E or with DNA (DAPI) plus basal (CK5) and luminal (CK8) differentiation markers.