ErbB2 Signaling Increases Androgen Receptor Expression in Abiraterone-Resistant Prostate Cancer

Purpose: ErbB2 signaling appears to be increased and may enhance AR activity in a subset of CRPC, but agents targeting ErbB2 have not been effective. This study was undertaken to assess ErbB2 activity in abiraterone-resistant prostate cancer (PCa), and determine whether it may contribute to androgen receptor (AR) signaling in these tumors. Experimental Design: AR activity and ErbB2 signaling were examined in the radical prostatectomy specimens from a neoadjuvant clinical trial of leuprolide plus abiraterone, and in the specimens from abiraterone-resistant CRPC xenograft models. The effect of ErbB2 signaling on AR activity was determined in two CRPC cell lines. Moreover, the effect of combination treatment with abiraterone and an ErbB2 inhibitor was assessed in a CRPC xenograft model. Results: We found that ErbB2 signaling was elevated in residual tumor following abiraterone treatment in a subset of patients, and was associated with higher nuclear AR expression. In xenograft models, we similarly demonstrated that ErbB2 signaling was increased and associated with AR reactivation in abiraterone-resistant tumors, while ERBB2 message level was not changed. Mechanistically, we show that ErbB2 signaling and subsequent activation of the PI3K/AKT signaling stabilizes AR protein. Inhibitors targeting ErbB2/PI3K/AKT pathway disrupt AR transcriptional activity. Furthermore, concomitantly treating CRPC xenograft with abiraterone and an ErbB2 inhibitor, lapatinib, blocked AR reactivation and suppressed tumor progression. Conclusions: ErbB2 signaling is elevated in a subset of abiraterone-resistant prostate cancer patients and stabilizes AR protein. Combination therapy with abiraterone and ErbB2 antagonists may be effective for treating the subset of CRPC with elevated ErbB2 activity

Null mutation for Macrophage Migration Inhibitory Factor (MIF) is associated with less aggressive bladder cancer in mice

<p>Abstract</p> <p>Background</p> <p>Inflammatory cytokines may promote tumorigenesis. Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine with regulatory properties over tumor suppressor proteins involved in bladder cancer. We studied the development of bladder cancer in wild type (WT) and MIF knockout (KO) mice given N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN), a known carcinogen, to determine the role of MIF in bladder cancer initiation and progression.</p> <p>Methods</p> <p>5-month old male C57Bl/6 MIF WT and KO mice were treated with and without BBN. Animals were sacrificed at intervals up to 23 weeks of treatment. Bladder tumor stage and grade were evaluated by H&E. Immunohistochemical (IHC) analysis was performed for MIF and platelet/endothelial cell adhesion molecule 1 (PECAM-1), a measure of vascularization. MIF mRNA was analyzed by quantitative real-time polymerase chain reaction.</p> <p>Results</p> <p>Poorly differentiated carcinoma developed in all BBN treated mice by week 20. MIF WT animals developed T2 disease, while KO animals developed only T1 disease. MIF IHC revealed predominantly urothelial cytoplasmic staining in the WT control animals and a shift toward nuclear staining in WT BBN treated animals. MIF mRNA levels were 3-fold higher in BBN treated animals relative to controls when invasive cancer was present. PECAM-1 staining revealed significantly more stromal vessels in the tumors in WT animals when compared to KOs.</p> <p>Conclusion</p> <p>Muscle invasive bladder cancer with increased stromal vascularity was associated with increased MIF mRNA levels and nuclear redistribution. Consistently lower stage tumors were seen in MIF KO compared to WT mice. These data suggest that MIF may play a role in the progression to invasive bladder cancer.</p

Regulation of the Prostaglandin Pathway During Development of Invasive Bladder Cancer in Mice

Prostaglandin E2 (PGE2) is reported to play an important role in tumor development. We explored the differential expression of genes governing production of, and response to, PGE2 during development of invasive bladder cancer. N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) or vehicle-treated mice (n = 4–5) were euthanized after 4–8 weeks (period 1, P1), 12–16 weeks (P2), and 20–23 weeks (P3). Half of each bladder was analyzed histologically and the other half extracted for mRNA analysis by quantitative real-time PCR. Bladders from BBN-treated mice showed progression from submucosal inflammation (P1) to squamous metaplasia/focal CIS (P2) to poorly differentiated, invasive cancer (P3). mRNA levels for the inducible cyclooxygenase, COX-2, were elevated three to fourfold at all time points in BBN-treated mice compared to controls. In contrast, mRNA levels for constitutive COX-1 and cytosolic phospholipase A2 (cPLA2), which releases substrate for COX, were either unchanged or decreased in BBN-treated mice relative to controls. Downstream of COX, mRNA levels of membrane-bound PGE2 synthase (mPGES-1) were increased 1.7-fold at P1 in BBN bladders but returned to control levels at P2 and P3. mRNA levels for 15-prostaglandin dehydrogenase (PGDH), which inactivates PGE2, were reduced 50–80% in BBN-treated bladders at all time points. mRNA levels for EP2R and EP4R, receptors for PGE2, were two to threefold increased at P1, but returned to control levels or below at P3. Hence, increased COX-2 and decreased PDGH expression occurred throughout tumor development, while mPGES-1, EP2R and EP4R were elevated only before development of invasive cancer. We compared expression of these genes in the malignant human urothelial cell lines, HTB-5 and HT-1376, with expression in a benign urothelial cell line, UROtsa. Neither malignant cell line reproduced the complete in vivo pattern, relative to benign cells, but each showed abnormal basal expression of several of the genes downstream of COX-2, but not COX-2 itself. We conclude that components involved in PGE2 synthesis and activity are differentially regulated during bladder tumor development and the therapeutic efficacy of targeting the various components may vary with stage of tumor development

H&E sections from representative time points for MIF WT and KO mice treated with BBN (+)

<p><b>Copyright information:</b></p><p>Taken from "Null mutation for Macrophage Migration Inhibitory Factor (MIF) is associated with less aggressive bladder cancer in mice"</p><p>http://www.biomedcentral.com/1471-2407/7/135</p><p>BMC Cancer 2007;7():135-135.</p><p>Published online 24 Jul 2007</p><p>PMCID:PMC1939709.</p><p></p> Arrows denote; subepithelial inflammation (4 week) and squamous metaplasia (8 week). High grade carcinoma is present at 20 weeks. Arrowheads show muscle cells with (WT+) and without (KO+) invasive carcinoma

Bladder cancer specimens from MIF WT (A, B) and KO (C, D) animals treated with BBN

<p><b>Copyright information:</b></p><p>Taken from "Null mutation for Macrophage Migration Inhibitory Factor (MIF) is associated with less aggressive bladder cancer in mice"</p><p>http://www.biomedcentral.com/1471-2407/7/135</p><p>BMC Cancer 2007;7():135-135.</p><p>Published online 24 Jul 2007</p><p>PMCID:PMC1939709.</p><p></p> A and C are representative areas of tumor with (A) and without (C) muscle invasion. B and D show immunohistochemical staining for vascular structures (arrowheads) by PECAM-1 in the same region. Note the marked increase in number of vessels in the WT animal (B) as compared to the KO (D)

Immunohistochemical staining for MIF in sections from MIF WT control (A), BBN treated mice with bladder cancer at 20 weeks (B) and human specimens from benign (C) and high-grade, invasive TCC (D)

<p><b>Copyright information:</b></p><p>Taken from "Null mutation for Macrophage Migration Inhibitory Factor (MIF) is associated with less aggressive bladder cancer in mice"</p><p>http://www.biomedcentral.com/1471-2407/7/135</p><p>BMC Cancer 2007;7():135-135.</p><p>Published online 24 Jul 2007</p><p>PMCID:PMC1939709.</p><p></p> Short arrows denote cytoplasmic staining in WT control and benign human tissue (A, C) with relatively scant nuclear staining. Long arrows denote cytoplasmic and intense nuclear staining in murine and human cancer tissue (B, D)