Effective treatment of HER2-amplified breast cancer by targeting HER3 and ß1 integrin.

The central role of HER2 as the disease driver and HER3 as its essential partner has made them rational targets for the treatment of HER2-amplifed breast cancers, and there is considerable interest in developing highly effective treatment regimens for this disease that consist of targeted therapies alone. Much of these efforts are focused on dual targeting approaches, particularly dual targeting of the HER2-HER3 tumor driver complex itself, or vertical combinations that target downstream PI3K or Akt in addition to HER2. There is also potential in lateral combinations based on evidence implicating cross-talk with other membrane receptor systems, particularly integrins, and such lateral combinations can potentially involve either HER2 or HER3. We established a preclinical model of targeting HER3 using doxycycline-inducible shRNA and determined the efficacy of a ß1 integrin inhibitor in combination with targeting HER3. We report that targeting HER3 and ß1 integrin provides a particularly effective combination therapy approach for HER2-amplified cancers, surpassing the combination of HER2 and ß1 integrin targeting, and evading some of the safety concerns associated with direct HER2-targeting. This further validates HER3 as a major hub mediating the tumorigenic functions of HER2 and identifies it as a high value target for lateral combination therapy strategies.

Prostate cancer metastasis: roles of recruitment and reprogramming, cell signal network and three-dimensional growth characteristics.

Prostate cancer (PCa) metastasizes to bone and soft tissues, greatly decreasing quality of life, causing bone pain, skeletal complications, and mortality in PCa patients. While new treatment strategies are being developed, the molecular and cellular basis of PCa metastasis and the "cross-talk" between cancer cells and their microenvironment and crucial cell signaling pathways need to be successfully dissected for intervention. In this review, we introduce a new concept of the mechanism of PCa metastasis, the recruitment and reprogramming of bystander and dormant cells (DCs) by a population of metastasis-initiating cells (MICs). We provide evidence that recruited and reprogrammed DCs gain MICs phenotypes and can subsequently metastasize to bone and soft tissues. We show that MICs can also recruit and reprogram circulating tumor cells (CTCs) and this could contribute to cancer cell evolution and the acquisition of therapeutic resistance. We summarize relevant molecular signaling pathways, including androgen receptors (ARs) and their variants and growth factors (GFs) and cytokines that could contribute to the predilection of PCa for homing to bone and soft tissues. To understand the etiology and the biology of PCa and the effectiveness of therapeutic targeting, we briefly summarize the animal and cell models that have been employed. We also report our experience in the use of three-dimensional (3-D) culture and co-culture models to understand cell signaling networks and the use of these attractive tools to conduct drug screening exercises against already-identified molecular targets. Further research into PCa growth and metastasis will improve our ability to target cancer metastasis more effectively and provide better rationales for personalized oncology.

Induction of integrin α2 in a highly bone metastatic human prostate cancer cell line: roles of RANKL and AR under three-dimensional suspension culture.

BACKGROUND: Prostate cancer (PCa) bone metastasis can be markedly enhanced by increased receptor activator of NF kappa-B ligand (RANKL) expression in PCa cells. Molecular mechanisms that account for the increased predilection of PCa for bone include increased bone turnover, promotion of PCa cell growth and survival in the bone environment, and recruitment of bystander dormant cells to participate in bone metastasis. The current study tests the hypothesis that PCa cells acquire high adhesion to bone matrix proteins, which controls PCa bone colonization, under the RANKL/RANK and AR axes. METHODS: We used a highly bone metastatic RANKL-overexpressing LNCaP PCa cell line, LNCaP(RANKL), as a model to pursue the molecular mechanisms underlying the increased adhesion of PCa cells to collagens. A three-dimensional (3-D) suspension PCa organoid model was developed. The functions of integrin α2 in cell adhesion and survival were evaluated by flow cytometry and western blot. AR expression and functionality were compared in 2-D monolayer versus 3-D suspension cultures using AR promoter- and PSA promoter-luciferase activity. AR role in cell adhesion was assessed using an adhesion assay. RESULTS: LNCaP(RANKL) cells were shown to adhere tightly to ColI matrix through increased α2 integrin expression. This increased adhesion, concomitant with activation of the FAK and Akt pathways, was further enhanced by culturing LNCaP(RANKL) cells in 3-D suspension. Under the influence of 3-D suspension culture, AR was restored in LNCaP(RANKL) cells via downregulation of AP-4 transcription factor, and supported increased α2 integrin expression and adhesion to ColI. CONCLUSION: 3-D suspension culture and in vivo PCa tumor growth restore AR through downregulation of AP-4, enhancing integrin α2 expression and adhesion to ColI which is rich in bone matrices. The interactions of PCa with ColI, mediated by integrin α2 and AR expression, could be a key molecular event accounting for PCa bone metastasis.

Sabutoclax, a Mcl-1 antagonist, inhibits tumorigenesis in transgenic mouse and human xenograft models of prostate cancer.

Resistance to available therapeutic agents has been a common problem thwarting progress in treatment of castrate-resistant and metastatic prostate cancer (PCa). Overexpression of the Bcl-2 family members, including Mcl-1, in PCa cells is known to inhibit intracellular mitochondrial-dependent apoptosis. Here we report the development of a novel transgenic mouse model that spontaneously develops prostatic intraepithelial neoplasia and adenocarcinoma by the inducible, conditional knockout of transforming growth factor ß receptor type II in stromal fibroblastic cells (Tgfbr2(ColTKO)). The Tgfbr2(ColTKO) prostate epithelia demonstrated down-regulation of luminal and basal differentiation markers, as well as Pten expression and up-regulation of Mcl-1. However, unlike in men, Tgfbr2(ColTKO) prostates exhibited no regression acutely after castration. The administration of Sabutoclax (BI-97C1), a pan-active Bcl-2 protein family antagonist mediated apoptosis in castrate-resistant PCa cells of Tgfbr2(ColTKO) mice and human subcutaneous, orthotopic, and intratibial xenograft PCa models. Interestingly, Sabutoclax had little apoptotic effect on benign prostate tissue in Tgfbr2(ColTKO) and wild-type mice. Sabutoclax was able to block c-Met activation, a critical axis in PCa metastatic progression. Further, Sabutoclax synergistically sensitized PC-3 cells to the cytotoxic effects of docetaxel (Taxotere). Together, these data suggest that Sabutoclax inhibits castrate-resistant PCa alone at the primary and bone metastatic site as well as support sensitivity to docetaxel treatment.

Variants in ZNF365 isoform D are associated with Crohn's disease.

OBJECTIVE: Genome-wide association studies have identified multiple Crohn's disease (CD) susceptibility loci, including association with non-coding intergenic single-nucleotide polymorphisms (SNPs) at 10q21. DESIGN: To fine-map the 10q21 locus, the authors genotyped 86 SNPs in 1632 CD cases and 961 controls and performed single-marker and conditional analyses using logistic regression. RESULTS: Association with CD risk spanning 11 SNPs (p<0.001) was observed. The most significant association observed was at the non-synonymous SNP, rs7076156 (Ala62Thr), in ZNF365. The alanine allele was over-represented in CD (p=5.23×10⁻7; OR=1.39 (95% CI 1.22 to 1.58)); allele frequency of 76% in CD and 69.7% in controls). Conditional analysis on rs7076156 nullified all other significant associations, suggesting that this is the causative variant at this locus. Four isoforms of ZNF365 have previously been identified, and rs7076156 is located in an exon unique to ZNF365 isoform D. The authors demonstrated, using reverse transcription-PCR, expression of ZNF365D in intestinal resections from both CD subjects and controls. Markedly reduced mean expression levels of ZNF365D were identified in Epstein-Barr virus-transformed lymphoblastoid cell lines from CD subjects homozygous for the risk allele (Ala). A whole-genome microarray expression study further suggested that the Ala62Thr change in ZNF365 isoform D is related to differential expression of the genes ARL4A, MKKS, RRAGD, SUMF2, TDR1 and ZNF148 in CD. CONCLUSIONS: Collectively, these data support the hypothesis that the non-synonymous Ala62Thr SNP, rs7076156, underlies the association between 10q21 and CD risk and suggest that this SNP acts by altering expression of genes under the control of ZNF365 isoform D.