HER-2 profiling and targeting in prostate carcinoma

Localized high-risk prostate cancer harbors an androgen receptor low subpopulation susceptible to HER2 inhibition

Patients diagnosed with localized high-risk prostate cancer have higher rates of recurrence, and the introduction of neoadjuvant intensive hormonal therapies seeks to treat occult micrometastatic disease by their addition to definitive treatment. Sufficient profiling of baseline disease has remained a challenge in enabling the in-depth assessment of phenotypes associated with exceptional vs. poor pathologic responses after treatment. In this study, we report comprehensive and integrative gene expression profiling of 37 locally advanced prostate tumors prior to six months of androgen deprivation therapy (ADT) plus the androgen receptor (AR) inhibitor enzalutamide prior to radical prostatectomy. A robust transcriptional program associated with HER2 activity was positively associated with poor outcome and opposed AR activity, even after adjusting for common genomic alterations in prostate cancer including PTEN loss and expression of the TMPRSS2:ERG fusion. Patients experiencing exceptional pathologic responses demonstrated lower levels of HER2 and phospho-HER2 by immunohistochemistry of biopsy tissues. The inverse correlation of AR and HER2 activity was found to be a universal feature of all aggressive prostate tumors, validated by transcriptional profiling an external cohort of 121 patients and immunostaining of tumors from 84 additional patients. Importantly, the AR activity-low, HER2 activity-high cells that resist ADT are a pre-existing subset of cells that can be targeted by HER2 inhibition alone or in combination with enzalutamide. In summary, we show that prostate tumors adopt an AR activity-low prior to antiandrogen exposure that can be exploited by treatment with HER2 inhibitors.

Active targeting schemes for nano-drug delivery systems in osteosarcoma therapeutics

Osteosarcoma, the most common malignant tumor of the bone, seriously influences people's lives and increases their economic burden. Conventional chemotherapy drugs achieve limited therapeutic effects owing to poor targeting and severe systemic toxicity. Nanocarrier-based drug delivery systems can significantly enhance the utilization efficiency of chemotherapeutic drugs through targeting ligand modifications and reduce the occurrence of systemic adverse effects. A variety of ligand-modified nano-drug delivery systems have been developed for different targeting schemes. Here we review the biological characteristics and the main challenges of current drug therapy of OS, and further elaborate on different targeting schemes and ligand selection for nano-drug delivery systems of osteosarcoma, which may provide new horizons for the development of advanced targeted drug delivery systems in the future.

LG. Phase II Trial of Pembrolizumab and Anti-CD3 x Anti-HER2 Bispecific Antibody-Armed Activated T Cells in Metastatic Castration-Resistant Prostate Cancer

PURPOSE

A phase II study was conducted to evaluate the safety and efficacy of the combination of HER2 bispecific antibody (HER2Bi)-armed activated T cells (HER2 BAT) and programmed death 1 inhibitor, pembrolizumab.

PATIENTS AND METHODS

Patients with metastatic castration-resistant prostate cancer (mCRPC) with 0 to 1 performance status and normal liver, kidney, and marrow function, pre- or post-docetaxel chemotherapy were eligible. Primary endpoint was 6-month progression-free survival (PFS). Peripheral blood mononuclear cells were obtained by a single apheresis, shipped to University of Virginia, activated with OKT3 and expanded for 14 days in IL2, harvested, and armed with HER2Bi and cryopreserved. HER2 BATs were infused twice weekly for 4 weeks and pembrolizumab was administered every 21 days for a maximum duration of 6 months starting 1 to 3 weeks prior to HER2 BATs infusion.

RESULTS

Fourteen patients were enrolled with a median age of 69 (range 57-82 years) and median PSA of 143.4 (range 8.2-4210 ng/dL). Two patients had peritoneal metastases, 1 had lymph node (LN) only metastases and 11 had bone metastases of which 7 had bone and LN metastases. All were pretreated with androgen receptor axis targeted agents and 7 (50%) had prior docetaxel chemotherapy. The toxicities were grade1-2 infusion reactions with fever, chills, headaches, nausea and/or myalgias. Primary endpoint of 6 month PFS was achieved in 5 of 14 patients (38.5%; 95% confidence interval, 19.5%-76.5%). Median PFS was 5 months and median survival was 31.6 months.

CONCLUSIONS

The safety and promising efficacy makes this combination worthy of future investigation in mCRPC.

Signaling Pathways That Control Apoptosis in Prostate Cancer

Prostate cancer is the second most common malignancy and the fifth leading cancer-caused death in men worldwide. Therapies that target the androgen receptor axis induce apoptosis in normal prostates and provide temporary relief for advanced disease, yet prostate cancer that acquired androgen independence (so called castration-resistant prostate cancer, CRPC) invariably progresses to lethal disease. There is accumulating evidence that androgen receptor signaling do not regulate apoptosis and proliferation in prostate epithelial cells in a cell-autonomous fashion. Instead, androgen receptor activation in stroma compartments induces expression of unknown paracrine factors that maintain homeostasis of the prostate epithelium. This paradigm calls for new studies to identify paracrine factors and signaling pathways that control the survival of normal epithelial cells and to determine which apoptosis regulatory molecules are targeted by these pathways. This review summarizes the recent progress in understanding the mechanism of apoptosis induced by androgen ablation in prostate epithelial cells with emphasis on the roles of BCL-2 family proteins and "druggable" signaling pathways that control these proteins. A summary of the clinical trials of inhibitors of anti-apoptotic signaling pathways is also provided. Evidently, better knowledge of the apoptosis regulation in prostate epithelial cells is needed to understand mechanisms of androgen-independence and implement life-extending therapies for CRPC.

Nanotreatment and Nanodiagnosis of Prostate Cancer: Recent Updates

The fabrication and development of nanomaterials for the treatment of prostate cancer have gained significant appraisal in recent years. Advancements in synthesis of organic and inorganic nanomaterials with charge, particle size, specified geometry, ligand attachment etc have resulted in greater biocompatibility and active targeting at cancer site. Despite all of the advances made over the years in discovering drugs, methods, and new biomarkers for cancer of the prostate (PCa), PCa remains one of the most troubling cancers among people. Early on, effective diagnosis is an essential part of treating prostate cancer. Prostate-specific antigen (PSA) or serum prostate-specific antigen is the best serum marker widely accessible for diagnosis of PCa. Numerous efforts have been made over the past decade to design new biosensor-based strategies for biomolecules detection and PSA miniaturization biomarkers. The growing nanotechnology is expected to have a significant effect in the immediate future on scientific research and healthcare. Nanotechnology is thus predicted to find a way to solve one of the most and long-standing problem, "early cancer detection". For early diagnosis of PCa biomarkers, different nanoparticles with different approaches have been used. In this review, we provide a brief description of the latest achievements and advances in the use of nanoparticles for PCa biomarker diagnosis.

Tumor Microenvironment-Derived NRG1 Promotes Antiandrogen Resistance in Prostate Cancer

Despite the development of second-generation antiandrogens, acquired resistance to hormone therapy remains a major challenge in treating advanced prostate cancer. We find that cancer-associated fibroblasts (CAFs) can promote antiandrogen resistance in mouse models and in prostate organoid cultures. We identify neuregulin 1 (NRG1) in CAF supernatant, which promotes resistance in tumor cells through activation of HER3. Pharmacological blockade of the NRG1/HER3 axis using clinical-grade blocking antibodies re-sensitizes tumors to hormone deprivation in vitro and in vivo. Furthermore, patients with castration-resistant prostate cancer with increased tumor NRG1 activity have an inferior response to second-generation antiandrogen therapy. This work reveals a paracrine mechanism of antiandrogen resistance in prostate cancer amenable to clinical testing using available targeted therapies.

Microenvironment-Mediated Resistance to Anti-Androgen Therapy

In this issue of Cancer Cell, Zhang et al. expose new possibilities for targeting castration-resistant prostate cancer (CRPC). Activation of the HER2/HER3 axis by cancer-associated fibroblast-secreted NRG1 mediates castration resistance, recommending novel applications of clinical anti-NRG1/HER3 therapeutics in treating CRPC.

Elimination of Osteosarcoma by Necroptosis with Graphene Oxide-Associated Anti-HER2 Antibodies

The prognosis for non-resectable or recurrent osteosarcoma (OS) remains poor. The finding that the majority of OS overexpress the protooncogene HER2 raises the possibility of using HER2 as a therapeutic target. However, clinical trials on the anti-HER2 antibody trastuzumab (TRA) in treating OS find no therapeutic benefit. HER2 overexpression in OS is not generally associated with gene amplification, with low-level expression regarded as HER2 “negative”, as per criteria used to classify breast cancer HER2 status. Nevertheless, active HER2-targeting approaches, such as virus-based HER2 vaccines or CAR-T cells have generated promising results. More recently, it has been found that the noncovalent association of TRA with nanomaterial graphene oxide (GO) generates stable TRA/GO complexes capable of rapidly killing OS cells. TRA/GO induces oxidative stress and strong HER2 signaling to elicit immediate degradation of both cIAP (cellular inhibitor of apoptosis protein) and caspase 8, leading to activation of necroptosis. This is an attractive mechanism of cancer cell death as chemo/apoptosis-resistant tumors may remain susceptible to necroptosis. In addition, necroptosis is potentially immunogenic to promote tumor immunity, as opposed to apoptosis that tends to silence tumor immunity. Currently, no established anticancer therapeutics are known to eliminate cancers by necroptosis. The aim of this article is to review the rationale and mechanisms of TRA/GO-mediated cytotoxicity.

Dacomitinib, but not lapatinib, suppressed progression in castration-resistant prostate cancer models by preventing HER2 increase

BACKGROUND

Despite overexpression of the ErbB (EGFR/HER2/ErbB3/ErbB4) family in castration-resistant prostate cancer (CRPC), some inhibitors of this family, including the dual EGFR/HER2 inhibitor lapatinib, failed in Phase II clinical trials. Hence, we investigated mechanisms of lapatinib resistance to determine whether alternate ErbB inhibitors can succeed.

METHODS

The CWR22 human tumour xenograft and its CRPC subline 22Rv1 and sera from lapatinib-treated CRPC patients from a previously reported Phase II trial were used to study lapatinib resistance. Mechanistic studies were conducted in LNCaP, C4-2 and 22Rv1 cell lines.

RESULTS

Lapatinib increased intratumoral HER2 protein, which encouraged resistance to this treatment in mouse models. Sera from CRPC patients following lapatinib treatment demonstrated increased HER2 levels. Investigation of the mechanism of lapatinib-induced HER2 increase revealed that lapatinib promotes HER2 protein stability, leading to membrane localisation, EGFR/HER2 heterodimerisation and signalling, elevating cell viability. Knockdown of HER2 and ErbB3, but not EGFR, sensitised CRPC cells to lapatinib. At equimolar concentrations, the recently FDA-approved pan-ErbB inhibitor dacomitinib decreased HER2 protein stability, prevented ErbB membrane localisation (despite continued membrane integrity) and EGFR/HER2 heterodimerisation, thereby decreasing downstream signalling and increasing apoptosis.

CONCLUSIONS

Targeting the EGFR axis using the irreversible pan-ErbB inhibitor dacomitinib is a viable therapeutic option for CRPC.

Her-2/Neu Receptor in Prostate Cancer Development and Progression to Androgen Independence

Development of prostate cancer and progression to androgen-independent disease is correlated with increased expression of growth factors and receptors capable of establishing autocrine and/or paracrine growth-stimulatory loops. A thorough review was made of the current literature and recent abstract presentations at scientific meetings focusing on the role of the HER-2/neu (c-erbB2) receptor in prostate cancer and the potential clinical usefulness of its specific inhibitors. In the past 10 years, conflicting results on HER-2/neu expression in prostate cancer have been reported. More recently, four studies have shown experimental evidence of HER-2/neu in the development of prostate cancer and, more specifically, in the progression to a hormone-refractory clinical behavior. Furthermore, it has been proposed that HER-2 family and androgen receptors function synergistically in the absence of androgen, which suggests a crosstalk between the HER-2/neu and androgen receptor pathways. Finally, clinical trials are in progress in prostate cancer patients to test novel agents that selectively interfere with HER-2/neu activity.

The evolving role of immunotherapy in prostate cancer

PURPOSE OF REVIEW

In recent clinical trials, immunotherapeutic agents have demonstrated promising results for the treatment of prostate cancer. This review discusses emerging immunotherapies for prostate cancer and their evolving role in sequencing and combination therapy.

RECENT FINDINGS

Therapeutic vaccines including PROSTVAC and DCVAC/PCa have completed promising phase 2 trials for the treatment of prostate cancer and phase 3 trials are underway. Recent evidence supports a synergistic relationship between immunotherapy agents themselves, antiandrogens and with cytotoxic chemotherapy. Prostate cancer patients with good prognostic factors, such as minimal disease burden, appear to achieve the optimal benefit from immunotherapy.

SUMMARY

Therapeutic cancer vaccines and immunomodulating agents have demonstrated activity in the treatment of prostate cancer. Immunotherapies may alter the prostate tumor microenvironment and ongoing studies aim to provide guidance on effective sequencing and combination strategies.

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

PURPOSE

ErbB2 signaling appears to be increased and may enhance androgen receptor (AR) activity in a subset of patients with castration-resistant prostate cancer (CRPC), but agents targeting ErbB2 have not been effective. This study was undertaken to assess ErbB2 activity in abiraterone-resistant prostate cancer and to determine whether it may contribute to 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. Mechanistically, we show that ErbB2 signaling and subsequent activation of the PI3K/AKT signaling stabilizes AR protein. Furthermore, concomitantly treating CRPC cells with abiraterone and an ErbB2 inhibitor, lapatinib, blocked AR reactivation and suppressed tumor progression.

CONCLUSIONS

ErbB2 signaling is elevated in a subset of patients with abiraterone-resistant prostate cancer and stabilizes AR protein. Combination therapy with abiraterone and ErbB2 antagonists may be effective for treating the subset of CRPC with elevated ErbB2 activity. Clin Cancer Res; 22(14); 3672-82. ©2016 AACR.

Significant intratumoral heterogeneity of human epidermal growth factor receptor 2 status in gastric cancer: A comparative study of immunohistochemistry, FISH, and dual-color in situ hybridization

The assessment of human epidermal growth factor receptor 2 (HER2) status is crucial for selecting patients with gastric cancer who may benefit from HER2‐targeted therapy. Accurate assessment using biopsy specimens is important for patients with advanced‐stage cancer. Intratumoral heterogeneity of HER2, however, is a major challenge in HER2 testing. Here, we aimed to examine whether assessment of HER2 status could be accurately carried out with currently used methods, namely, immunohistochemistry (IHC), FISH, and dual‐color in situ hybridization (DISH). Human epidermal growth factor receptor 2 status was evaluated in 108 biopsy tissues from patients with gastric adenocarcinoma and 70 matched surgical specimens by IHC, FISH, and DISH; HER2 amplification was detected in 11 (10.2%) out of 108 biopsy specimens. The IHC and FISH results were well correlated, and FISH and DISH results were consistent for all cases. The overall concordance rate of HER2 status between biopsy tissues and surgical specimens was 91.4%. All six discordant cases were false negative on biopsy; of these cases, five showed HER2 heterogeneity on surgical resection. Assessment of the HER2 status of biopsy tissues could predict the status of the whole tumor; however, a proportion of these cases may be discordant because of intratumoral heterogeneity.

This study demonstrated that HER2 assessment in biopsy tissues may predict the HER2 status of the whole tumor by IHC, FISH, and DISH. However, some cases of discordance may occur because of intratumoral HER2 heterogeneity in gastric cancers. In cases of intratumoral heterogeneity, more accurate HER2 assessment can be achieved by analysis of whole sections and by using a combination of IHC and DISH, if possible.

VEGFR-1 overexpression identifies a small subgroup of aggressive prostate cancers in patients treated by prostatectomy

The VEGFR-1 is suggested to promote tumor progression. In the current study we analyzed prevalence and prognostic impact of the VEGFR-1 by immunohistochemistry on a tissue microarray containing more than 3000 prostate cancer specimens. Results were compared to tumor phenotype, ETS-related gene (ERG) status, and biochemical recurrence. Membranous VEGFR-1 expression was detectable in 32.6% of 2669 interpretable cancers and considered strong in 1.7%, moderate in 6.7% and weak in 24.2% of cases. Strong VEGFR-1 expression was associated with TMPRSS2:ERG fusion status as determined by fluorescence in situ hybridization (FISH) and immunohistochemistry (p < 0.0001 each). Elevated VEGFR-1 expression was linked to high Gleason grade and advanced pT stage in TMPRSS2:ERG negative cancers (p = 0.0008 and p = 0.001), while these associations were absent in TMPRSS2:ERG positive cancers. VEGFR-1 expression was also linked to phosphatase and tensin homolog (PTEN) deletions. A comparison with prostate specific antigen (PSA) recurrence revealed that the 1.7% of prostate cancers with the highest VEGFR-1 levels had a strikingly unfavorable prognosis. This could be seen in all cancers, in the subsets of TMPRSS2:ERG positive or negative, PTEN deleted or undeleted carcinomas (p < 0.0001 each). High level VEGFR-1 expression is infrequent in prostate cancer, but identifies a subgroup of aggressive cancers, which may be candidates for anti-VEGFR-1 targeted therapy.

Discordances in HER2 status between primary gastric cancer and corresponding metastatic sites

OBJECTIVE

Determination of human epidermal growth factor receptor-2 status in advanced gastric cancer is important in clinical decision making. In the trastuzumab for GC trial, trastuzumab-based therapy demonstrated a significant overall survival benefit in patients with human epidermal growth factor receptor-2-positive advanced gastric cancer. Human epidermal growth factor receptor-2 discordance in gastric cancer primary and its metastases has been long debated. The aim of the study was to evaluate the rate of human epidermal growth factor receptor-2 discordance and its effect on treatment decisions in advanced gastric cancer.

METHODS

A total of 74 patients with advanced gastric cancer were included in the study. Both immunohistochemical staining and dual-color silver in situ hybridization were performed in all patients to evaluate the human epidermal growth factor receptor-2 status of the primary lesion and paired metastasis.

RESULTS

The assessment of human epidermal growth factor receptor-2 status with the immunohistochemical staining method and dual-color silver in situ hybridization revealed a discordance rate of 9.5 and 16.2%, respectively. However, this discordance was clinically meaningful in only one patient leading to a change in treatment decision. While this patient had a human epidermal growth factor receptor-2-negative status in primary tumor (immunohistochemical = 0, dual-color silver in situ hybridization = negative), the human epidermal growth factor receptor-2 status was positive for liver metastasis (immunohistochemical = 2+, dual-color silver in situ hybridization = positive). Trastuzumab was added to the chemotherapy regimen.

CONCLUSIONS

In this study, we found a higher rate of human epidermal growth factor receptor-2 discordance between primary gastric tumor and metastatic lesions compared with the rates reported in previous studies. Detection of a human epidermal growth factor receptor-2-positive metastasis with a human epidermal growth factor receptor-2-negative primary tumor suggests that investigation of human epidermal growth factor receptor-2 is also required for the metastatic lesion and that trastuzumab could be administered in the case of a positive result.

Phase I Study of Anti-CD3 x Anti-Her2 Bispecific Antibody in Metastatic Castrate Resistant Prostate Cancer Patients

Background. New nontoxic targeted approaches are needed for patients with castrate resistant prostate cancer (CRPC). Our preclinical studies show that activated T cells (ATC) armed with anti-CD3 x anti-Her2 bispecific antibody (Her2Bi) kill prostate cancer cells lines, induce a Th1 cytokine pattern upon engagement of tumor cells, prevent the development of prostate tumors, and retard tumor growth in immunodeficient mice. These studies provided strong rationale for our phase I dose-escalation pilot study to test ATC armed with Her2Bi (aATC) for safety in men with CRPC. Methods. Seven of 8 men with CRPC were evaluable after receiving two infusions per week for 4 weeks. The men received 2.5, 5 or 10 × 10(9) aATC per infusion with low dose interleukin-2 and granulocyte-macrophage colony stimulating factor. Results. There were no dose limiting toxicities, and there was 1 partial responder and 3 of 7 patients had significant decreases in their PSA levels and pain scores. Immune evaluations of peripheral blood mononuclear cells in 2 patients before and after immunotherapy showed increases in IFN-γ EliSpot responses and Th1 serum cytokines. Conclusions. These results provide a strong rationale for developing phase II trials to determine whether aATC are effective for treating CRPC.

Antibody targeting of HER2/HER3 signaling overcomes heregulin-induced resistance to PI3K inhibition in prostate cancer

Dysregulated expression and/or mutations of the various components of the phosphoinositide 3-kinase (PI3K)/Akt pathway occur with high frequency in prostate cancer and are associated with the development and progression of castration resistant tumors. However, small molecule kinase inhibitors that target this signaling pathway have limited efficacy in inhibiting tumor growth, primarily due to compensatory survival signals through receptor tyrosine kinases (RTKs). Although members of the epidermal growth factor receptor (EGFR), or HER, family of RTKs are strongly implicated in the development and progression of prostate cancer, targeting individual members of this family such as EGFR or HER2 has resulted in limited success in clinical trials. Multiple studies indicate a critical role for HER3 in the development of resistance against both HER-targeted therapies and PI3K/Akt pathway inhibitors. In this study, we found that the growth inhibitory effect of GDC-0941, a class I PI3K inhibitor, is markedly reduced in the presence of heregulin. Interestingly, this effect is more pronounced in cells lacking phosphatase and tensin homolog function. Heregulin-mediated resistance to GDC-0941 is associated with reactivation of Akt downstream of HER3 phosphorylation. Importantly, combined blockade of HER2 and HER3 signaling by an anti-HER2/HER3 bispecific antibody or a mixture of anti-HER2 and anti-HER3 antibodies restores sensitivity to GDC-0941 in heregulin-treated androgen-dependent and -independent prostate cancer cells. These studies indicate that the combination of PI3K inhibitors with HER2/HER3 targeting antibodies may constitute a promising therapeutic strategy for prostate cancer.

Heterogeneity of ERBB2 in gastric carcinomas: a study of tissue microarray and matched primary and metastatic carcinomas

Trastuzumab in association with systemic cytotoxic chemotherapy is a therapeutic option for patients with advanced or metastatic ERBB2+ gastric carcinoma. The status of the ERBB2 overexpression or gene amplification is an important predictive marker in gastric cancer. However, it is controversial whether the primary tumor is representative of distant metastases in terms of ERBB2 status. Quadruplicated tissue microarrays from formalin-fixed paraffin-embedded tissues from 498 advanced primary gastric carcinomas and 97 matched metastatic lymph nodes were investigated by immunohistochemistry with HercepTest and silver in situ hybridization. For further comparison, another set of 41 paired primary and distant metastatic gastric carcinomas were also tested. Intratumoral heterogeneity was defined as different results between tissue microarray cores. ERBB2-positivity was observed in 52 gastric carcinomas (10%) and was not associated with recurrence of disease or survival of patients. In ERBB2-positive primary gastric carcinomas, heterogeneous ERBB2 overexpression was observed in 21/63 (33%) gastric carcinomas and heterogeneous ERBB2 gene amplification in 14/62 (23%) cases. Repeated immunohistochemistry and silver in situ hybridization in representative paraffin tumor blocks confirmed focal ERBB2 overexpression and ERBB2 gene amplification and did not change the final results. Discrepancies in ERBB2 results between primary and paired metastatic lymph nodes were observed in 11% of cases by immunohistochemistry and 7% by silver in situ hybridization. Out of the 41 paired primary and distant metastases, 5 (12%) cases were ERBB2-positive, and discrepancy was observed in one case. Intratumoral heterogeneity and discrepant ERBB2 results in primary and metastatic tumor are not uncommon in gastric carcinoma. Results of silver in situ hybridization showed less frequent heterogeneity compared with immunohistochemistry. Wherever possible, ERBB2 immunohistochemistry testing should be performed in both primary and distant metastatic sites.

Validation of a multiplex immunoassay for serum angiogenic factors as biomarkers for aggressive prostate cancer

BACKGROUND

Assays used for discovery of biomarkers should be robust and high-throughput, capable of analyzing a sufficiently large number of samples over a sufficiently long period of time with good precision.

METHODS

We evaluated the analytical performance of the Bio-Plex Pro™ Human Cancer Biomarker Panel 1, a 16-plex multiplex immunoassay, in serum for composite profiling of angiogenic factors. Because prostate cancer progression and metastasis are pathological events closely linked to angiogenesis, serum angiogenic factors are ideal candidates as prognostic biomarkers.

RESULTS

Our 5-day evaluation indicated that all 16 assays in the panel had good reproducibility (total precisions over 5 independent plates in 5 days of <20%), adequate sensitivity (LOQs of majority of the assays less than 100 pg/ml), and wide dynamic ranges (linearity of majority of the assays spanning across 3 logs in concentrations).

CONCLUSIONS

Applying the panel to sera from prostate cancer patients with Gleason scores of 6, 7, 8-10, tumor stages that correlated with clinical outcome, we identified that the levels of sTIE-2, a soluble form of the transmembrane tyrosine kinase receptor for angiopoietins, were increased in patients with Gleason score of 8-10. Future studies are necessary to determine whether sTIE-2 could be used as a prognostic biomarker for identifying aggressive prostate cancer.

Targeted therapy for gastric cancer--current status

In patients with metastatic gastric cancer, median overall survival remains under 1 year and standard chemotherapy regimens are not able to substantially improve the prognosis of the patients. Amplification and over-expression of HER2 is reported in approximately 20% of gastric tumours, challenging the use of targeted therapies. There are several targeted therapies in different stages of clinical development with trastuzumab being the first overcoming the regulatory hurdle and getting European Medicines Agency approval. In patients with advanced gastric or gastro-oesophageal junction cancer, addition of trastuzumab to chemotherapy significantly improved overall survival compared with chemotherapy alone. Addition of trastuzumab to chemotherapy did not increase the incidence of adverse events. Other agents targeting the HER2 pathway (lapatinib) or other domains of epidermal growth factor receptor family (cetuximab) are currently being investigated for the treatment of an advanced gastric cancer.

Small-molecule protein tyrosine kinase inhibitors for the treatment of metastatic prostate cancer

The microenvironment is critical to the growth of prostate cancer (PCa) in the bone. Thus, for clinical efficacy, therapies must target tumor-microenvironment interactions. Several protein tyrosine kinases have been implicated in the development and growth of PCa bone metastasis. In this review, specific protein tyrosine kinases that regulate these complex interactions, including PDGFR, the EGFR family, c-Src, VEGFR, IGF-1R, FGFR and c-Met will be discussed, with an emphasis on why these kinases are promising therapeutic targets for metastatic PCa treatment. For each of these kinases, small-molecule inhibitors have reached clinical trials. Current results of these trials and future prospects for the use of tyrosine kinase inhibitors for the treatment of PCa bone metastases are also discussed.

Castration-resistant prostate cancer: new science and therapeutic prospects

There is a growing number of new therapies targeting different pathways that will revolutionize patient management strategies in castration-resistant prostate cancer (CRPC) patients. Today there are more clinical trial options for CRPC treatment than ever before, and there are many promising agents in late-stage clinical testing. The hypothesis that CRPC frequently remains driven by a ligand-activated androgen receptor (AR) and that CRPC tissues exhibit substantial residual androgen levels despite gonadotropin-releasing hormone therapy, has led to the evaluation of new oral compounds such as abiraterone and MDV 3100. Their results, coupled with promising recent findings in immunotherapy (eg sipuleucel-T) and with agents targeting angiogenesis (while awaiting the final results of the CALGB trial 90401) will most probably impact the management of patients with CRPC in the near future. Other new promising agents need further development. With our increased understanding of the biology of this disease, further trial design should incorporate improved patient selection so that patient populations are those who may be most likely to benefit from treatment.

A transductionally retargeted adenoviral vector for virotherapy of Her2/neu-expressing prostate cancer

The efficacy of adenovirus (Ad)-based gene therapy of solid tumors, such as prostate cancer, is limited. One of the many problems is that the virus infects many different cell types in the body, resulting in high toxicity, whereas the target cancer cells are often less prone to wild-type Ad infection. Our aim was to develop genetically de- and retargeted Ad vectors to reduce off-target effects and increase target infection for prostate cancer. We have previously reported an Ad5 vector specific for the cancer-associated receptor Her2/neu, created by inserting Her2/neu-reactive Affibody(®) molecules (ZH) into the HI loop of a coxsackievirus and adenovirus receptor binding-ablated fiber (Ad[ZH/1]). In addition to virus retargeting to Her2/neu, this virus was further modified from wild-type Ad by changing the RGD motif in the penton base to EGD and by substitution of the KKTK motif in the third shaft repeat to RKSK, resulting in the vector Ad[ZH/3]. The ZH-containing vectors could be produced to high titers and were specific for their target, resulting in efficient infection and killing of Her2/neu-positive androgen-dependent PC346C prostate cancer cells in vitro. Here we show that the oncolytic Ad[ZH/3] vector significantly prolonged survival time and reduced serum prostate-specific antigen levels in an orthotopic prostate tumor model in nude mice to the same extent as wild-type Ad5. Our results show that Her2/neu targeting using Ad-based vectors for prostate cancer is feasible and may serve as a basis for the development of gene therapy of human prostate cancer as well as other Her2/neu-expressing cancers.

Dual EGFR/HER2 inhibition sensitizes prostate cancer cells to androgen withdrawal by suppressing ErbB3

PURPOSE

Patients with recurrent prostate cancer are commonly treated with androgen withdrawal therapy (AWT); however, almost all patients eventually progress to castration resistant prostate cancer (CRPC), indicating failure of AWT to eliminate androgen-sensitive prostate cancer. The overall goal of these studies is to determine whether dual inhibition of the receptor tyrosine kinases epidermal growth factor receptor (EGFR) and HER2 would prolong the effectiveness of this treatment in prostate cancer.

EXPERIMENTAL DESIGN

We used androgen-dependent LNCaP cells and its CRPC sublines LNCaP-AI and C4-2. Additional data were collected in pRNS-1-1 cells stably expressing a mutant androgen receptor (AR-T877A), and in nude mice harboring CWR22 tumors. Studies utilized EGFR inhibitors erlotinib and AG1478, and HER2 inhibitors trastuzumab and AG879.

RESULTS

Dual EGFR/HER2 inhibition induced apoptosis selectively in androgen-sensitive prostate cancer cells undergoing AWT, but not in the presence of androgens, or in CRPC cells. We show that AWT alone failed to induce significant apoptosis in androgen-dependent cells, due to AWT-induced increase in HER2 and ErbB3, which promoted survival by increasing Akt phosphorylation. AWT-induced ErbB3 stabilized the AR and stimulated PSA, while it was inactivated only by inhibition of both its dimerization partners EGFR and HER2 (prostate cancer cells do not express ErbB4); but not the inhibition of any one receptor alone, explaining the success of dual EGFR/HER2 inhibition in sensitizing androgen-dependent cells to AWT. The effectiveness of the inhibitors in suppressing growth correlated with its ability to prevent Akt phosphorylation.

CONCLUSION

These studies indicate that dual EGFR/HER2 inhibition, administered together with AWT, sensitize prostate cancer cells to apoptosis during AWT.

Her-2/neu gene amplification and over-expression in stomach and esophageal adenocarcinoma: from pathology to treatment

Discovery of the over-expression of Her-2/neu or the amplification of its regulatory gene in stomach and esophageal cancer has resulted in targeted treatment directed at this protein. The fact itself and its consequences have been the topic of an abundance of studies and clinical trials. In the present report we review the current state of the art as regards diagnosis of the over-expression and amplification of Her-2/neu, its inhibition as a new therapeutic concept, treatment toxicity, and the development of resistance to Her-2/neu as a limiting factor in stomach and esophageal adenocarcinoma.

A phase II study of lapatinib, a dual EGFR and HER-2 tyrosine kinase inhibitor, in patients with castration-resistant prostate cancer

OBJECTIVES

Epidermal growth factor receptor (EGFR) and HER-2 tyrosine kinases may be involved in activation of androgen receptor and progression of prostate cancer. They represent potential therapeutic targets in prostate cancer. Lapatinib is an oral inhibitor of EGFR and HER-2. The objective of this study is to assess the preliminary clinical efficacy of lapatinib in the therapy of castration-resistant prostate cancer.

METHODS

In this multicenter, open-label trial, patients with rising PSA on androgen deprivation therapy and not having received chemotherapy were eligible. They were treated with lapatinib at a dose of 1,500 mg once daily. The primary end point was a >50% confirmed PSA decline from baseline; safety, tolerability, and time to PSA progression were secondary outcomes.

RESULTS

Twenty-nine patients enrolled in the study had a median age of 73 years and a baseline PSA of 21.6 ng/ml. Seven patients had no radiologic evidence of metastatic disease, while the remaining patients had bone or measurable disease or both. Treatment was well tolerated with only grade 3 treatment-related toxicities being diarrhea (14%) and rash (3%). One of 21 evaluable patients had >50% reduction in PSA, while another patient had 47% reduction in PSA with an ongoing duration of response of 45+ months. The median time to PSA progression was 29 days.

CONCLUSIONS

Lapatinib showed single agent activity in a small subset of unselected patients with castration-resistant prostate cancer, as measured by PSA. Future trials should explore a trial design with time-to-event end points and predictive biomarkers and a combination with other agents.

High level PSMA expression is associated with early PSA recurrence in surgically treated prostate cancer

BACKGROUND

Prostate specific membrane antigen (PSMA) is a suggested target for antibody-based therapy of prostate cancer potentially involved in the regulation of cell migration. This study was undertaken, to gain more insight on the role of PSMA in early prostate cancer and its distribution in various normal tissues.

METHODS

A total of 1,700 different prostate cancers treated by radical prostatectomy and 612 samples from 76 different normal tissue types were successfully analyzed by immunohistochemistry (IHC) in a tissue microarray (TMA) format. PSMA immunostaining in cancers was also compared with clinical follow-up, preexisting HER2 expression and Ki67 labeling index data.

RESULTS

PSMA staining was only found in prostate epithelium and expression was higher in cancer cells than in benign tissue. PSMA staining was found in 94.1% of cancers and was significantly associated with tumor stage, high Gleason grade, preoperative PSA, and HER2 expression (P < 0.0001 each). Tumors with strong PSMA expression had a higher risk of biochemical recurrence than cancers with only weak PSMA staining intensity (P = 0.0483). There was no significant association between PSMA expression and Ki67 labeling index (P = 0.442).

CONCLUSIONS

Based on the high frequency of PSMA overexpression in all stages and grades of prostate cancer and the high prevalence of PSMA overexpression, it can be speculated that increased PSMA expression may be related with prostate cancer development rather than progression. The known function of PSMA activating cell migration would be in line with the suggested role in cancer progression and the missing association between PSMA overexpression and tumor cell proliferation.

Low level HER2 overexpression is associated with rapid tumor cell proliferation and poor prognosis in prostate cancer

PURPOSE

The HER2 oncogene is involved in the biology of many different tumor types and serves as a prognostic marker and a therapeutic target in breast cancer. In contrast to breast cancer, studies on Her2 overexpression and gene amplification in prostate cancer have yielded different results. The purpose of this study was to learn more on the prevalence and clinical significance of HER2 amplification and overexpression in prostate cancer.

EXPERIMENTAL DESIGN

A tissue microarray containing >2,000 prostate cancers with follow-up data was used. Tissue microarray sections were analyzed on protein and DNA level using two different antibodies (HercepTest, DAKO; Novocastra NCL-CB11) and fluorescence in situ hybridization.

RESULTS

Immunohistochemical analyses showed highly similar results for both antibodies. Detectable Her2 immunostaining was observed in 17.2% for the HercepTest and in 22.5% for the Novocastra antibody with the vast majority of cases showing 1+ or 2+ staining. For both antibodies (HercepTest/Novocastra), significant associations were found between positive staining and high Gleason grade (P < 0.0001, both), advanced pT stage (P < 0.0001/P = 0.0015), rapid tumor cell proliferation (P = 0.0004/P = 0.0071), and tumor recurrence (P < 0.0001, both). HER2 amplification was only found in 1 of 2,525 analyzable cases (0.04%).

CONCLUSIONS

Low-level Her2 overexpression occurs at relevant frequency in prostate cancer and in the absence of gene amplification. Increased Her2 expression may potentially lead to an aggressive behavior of tumor cells through the stimulation of tumor cell proliferation because Her2 staining was shown to be significantly associated with Ki67 labeling index. These data argue for reconsidering anti-Her2 therapy, possibly with modified approaches.

Lentiviruses with trastuzumab bound to their envelopes can target and kill prostate cancer cells

In this study, we took advantage of the overexpression of human epidermal growth factor receptor 2 (HER-2) in prostate cancers to design lentiviruses with modified envelope proteins that bind antibodies to specific cell-surface antigens. When bound to trastuzumab (Herceptin, Genentech, CA), lentiviruses were able to selectively infect androgen-sensitive LNCaP and castration-resistant C4-2 human prostate cancer cell lines, both of which express high levels of HER-2. To test for a therapeutic effect, we engineered our antibody-binding lentiviruses to express thymidine kinase, which can convert the non-toxic pro-drug ganciclovir (GCV) into a cytotoxic form. LNCaP and C4-2 cells infected by these viruses were sensitive to GCV killing. In vivo, C4-2 xenograft tumors treated either intratumorally or i.v. with trastuzumab-bound lentivirus expressed luciferase, although the latter route was less tumor specific. When a prostate-specific promoter for governing luciferase expression was combined with trastuzumab-mediated delivery, there was a further enrichment in targeting viral gene expression in prostate tumors. In conclusion, we found that although prostate cancers that express high levels of HER-2 are resistant to the killing effects of trastuzumab, they can be targeted for selective gene expression and destruction by viruses with envelope proteins engineered to bind this antibody.

Androgen receptor: role and novel therapeutic prospects in prostate cancer

Androgen receptor (AR) signaling is necessary for the development of prostate cancer. Androgen-deprivation therapy (ADT) for prostate cancer was described over 50 years ago and ADT remains the mainstay of systemic therapy. AR signaling remains intact as the disease evolves to castration-resistant prostate cancer (CRPC). Through cellular adaptations, CRPC continues to rely on androgens and AR growth signaling, and thus AR remains an important therapeutic target. CRPC cells upregulate enzymes used in androgen synthesis, thus providing an intracellular source of androgen despite systemic castration. Compounds in development, such as antiandrogens, lyase inhibitors, heat-shock protein-90 inhibitors, histone deacetylase inhibitors and others, will provide new tools to more effectively reduce ligand, inhibit AR and/or inhibit costimulatory pathways and result in improved clinical outcomes.

Elevated levels of HER-2/neu and androgen receptor in clinically localized prostate cancer identifies metastatic potential

BACKGROUND

In this study, we investigated the expression of HER-2/neu and AR in clinically organ-confined prostate cancer to determine whether alterations in these signaling pathways contribute to the development of metastatic disease.

METHODS

HER-2/neu and AR immunoreactivity were evaluated in archived prostatic tissues obtained from 53 men with clinically organ-confined disease who underwent radical prostatectomy. Associations between AR and HER-2/neu immunostaining and disease outcome were determined.

RESULTS

Seventy percent (37/53) of tumors exhibited high levels of HER-2/neu immunostaining and 68% (36/53) of tumors had elevated AR levels. Patients with high levels of both HER-2/neu and AR had the highest rate of PSA failure (56%, 15/27) compared with no PSA failures amongst seven patients with low levels of both HER-2/neu and AR (log rank statistic 7.69, P = 0.021). Concurrent high levels of HER-2/neu and AR expression were significantly associated with high pathological stage (P = 0.027) and development of metastatic disease (P = 0.022).

CONCLUSIONS

These findings support the notion that both the HER-2/neu and AR signaling pathways may contribute to development of metastatic disease. The subset of prostate tumors with increased HER-2/neu and AR levels may benefit from treatment strategies that target both signaling pathways.

Cyclooxygenase-2 (COX-2): a molecular target in prostate cancer

Epidemiological studies provided the first evidence that COX may be involved in the pathogenesis of cancer. In the process of carcinogenesis and in the route of intracellular signalling during carcinogenesis, COX-2 expression may be a universal phenomenon. In general, COX-2 is up-regulated throughout the tumorigenic process, from early hyperplasia to metastatic disease. COX-2 has been reported to be constitutively overexpressed in a variety of malignancies and is frequently constitutively elevated in prostate carcinoma. COX-2 was consistently overexpressed in premalignant lesions such as prostatic intraepithelial neoplasia, and carcinoma. Cases are described with evolution of proliferative inflammatory atrophy of the prostate and prostate carcinoma. The increase of evidence implicating COX-2 in cancer has stimulated clinical trials to investigate the efficacy of selective COX-2 inhibitors in individuals at risk for human cancer. Regarding prostate carcinoma there is much direct or indirect evidence to support the use of COX-2 inhibitors in this disease. Trials using these drugs in familial adenomatous polyposis (FAP) and other patients with a high risk of colorectal carcinoma are ongoing.

Monoclonal antibody therapy for prostate cancer

Early detection of prostate cancer (PCa) and advances in hormonal and chemotherapy treatments have provided great clinical benefits to patients with early stages of the disease. However, a significant proportion of patients still progress to advanced, metastatic disease, for which no effective therapies are available. Therefore, there is a critical need for new treatment modalities, ideally targeted specifically to prostate cancer cells. The recent clinical and commercial successes of monoclonal antibodies (MAbs) have made them the most rapidly expanding class of therapeutics being developed for many disease indications, including cancer. PCa is well suited for antibody-based therapy due to the size and location of recurrent and metastatic tumors, and the lack of necessity to avoid targeting the normal prostate, a nonessential organ. These properties have fostered interest in the development and clinical evaluation of therapeutic MAbs directed to both well established and newly discovered targets in PCa. MAbs directed to established targets include those approved for other solid tumors, including anti-human epidermal growth factor receptor-2 (HER2) MAb trastuzumab, anti-epidermal growth factor receptor (EGFR) MAbs cetuximab and panitumumab, and the antivascular endothelial growth factor (VEGF) MAb bevacizumab. Genomics efforts have yielded a large number of novel, clinically relevant targets in PCa with the desirable expression profiling in tumor and normal tissues, and with an implicated role in tumor growth and spread. Growing efforts are directed to the development of naked or payload-conjugated therapeutic antibodies to these targets, and a variety of MAb products are currently progressing through preclinical and various stages of clinical development. The clinical experience with some of the commercialized MAb products points out specific challenges in conducting clinical trials with targeted therapy in PCa.

Preoperative Plasma HER2 and Epidermal Growth Factor Receptor for Staging and Prognostication in Patients with Clinically Localized Prostate Cancer

PURPOSE

Human epidermal growth factor receptor-2 (HER2) and epidermal growth factor receptor (EGFR) expression have been associated with disease progression in patients with prostate cancer. We tested the hypothesis that plasma levels of HER2 and/or EGFR are associated with prostate cancer stage and prognosis in patients with clinically localized disease.

EXPERIMENTAL DESIGN

We measured preoperative plasma HER2 and EGFR levels using commercially available ELISAs on banked plasma from 227 patients treated with radical prostatectomy and bilateral lymphadenectomy for clinically localized prostate adenocarcinoma.

RESULTS

Median preoperative plasma EGFR and HER2 levels were 31.4 ng/mL (interquartile range, 19.2 ng/mL) and 10.0 ng/mL (interquartile range, 2.7 ng/mL), respectively. HER2 was elevated in patients with seminal vesicle invasion (P = 0.033). In separate multivariate analyses that adjusted for the effects of standard preoperative predictors, lower EGFR, higher HER2, and higher HER2/EGFR ratio were associated with prostate-specific antigen (PSA) progression (P = 0.003, P < 0.001, and P < 0.001, respectively). In separate multivariate analyses that adjusted for the effects of standard postoperative predictors, lower EGFR and higher HER2/EGFR ratio were associated with PSA progression (P = 0.027 and P < 0.001, respectively). Among the patients who experienced PSA progression, HER2 was significantly higher (P = 0.023) and EGFR was lower (P = 0.04) in those with features of aggressive disease (i.e., development of metastasis, PSA doubling time <10 months, and/or failure to respond to local salvage radiation therapy).

CONCLUSION

Preoperative plasma HER2 and EGFR were associated with prostate cancer progression after radical prostatectomy. Plasma HER2 and EGFR may provide a tool for predicting long-term recurrence-free survival and early metastasis.

Circulating tumor cell analysis in patients with progressive castration-resistant prostate cancer

PURPOSE

To better direct targeted therapies to the patients with tumors that express the target, there is an urgent need for blood-based assays that provide expression information on a consistent basis in real time with minimal patient discomfort. We aimed to use immunomagnetic-capture technology to isolate and analyze circulating tumor cells (CTC) from small volumes of peripheral blood of patients with advanced prostate cancer.

EXPERIMENTAL DESIGN

Blood was collected from 63 patients with metastatic prostate cancer. CTCs were isolated by the Cell Search system, which uses antibodies to epithelial cell adhesion marker and immunomagnetic capture. CTCs were defined as nucleated cells positive for cytokeratins and negative for CD45. Captured cells were analyzed by immunofluorescence, Papanicolau staining, and fluorescence in situ hybridization.

RESULTS

Most patients (65%) had 5 or more CTCs per 7.5 mL blood sample. Cell counts were consistent between laboratories (c = 0.99) and did not change significantly over 72 or 96 h of storage before processing (c = 0.99). Their identity as prostate cancer cells was confirmed by conventional cytologic analysis. Molecular profiling, including analysis of epidermal growth factor receptor (EGFR) expression, chromosome ploidy, and androgen receptor (AR) gene amplification, was possible for all prostate cancer patients with >or=5 CTCs.

CONCLUSIONS

The analysis of cancer-related alterations at the DNA and protein level from CTCs is feasible in a hospital-based clinical laboratory. The alterations observed in EGFR and AR suggest that the methodology may have a role in clinical decision making.

ErbB-2 induces the cyclin D1 gene in prostate epithelial cells in vitro and in vivo

The receptor tyrosine kinase ErbB-2 plays an important role in the regulation of growth factor-induced signal transduction cascades in the epithelium, and ErbB-2 is frequently overexpressed in epithelial tumors. Our previous studies on clinical prostate cancer specimens indicated that ErbB-2 expression was increased in patients undergoing hormone ablation therapy. We had also shown that the critical cell cycle regulatory gene cyclin D1 and its promoter were targets of proliferative signaling in prostate cancer cell lines, and that cyclin D1 was required for ErbB-2-induced mammary tumorigenesis. In the current studies, we found that increased ErbB-2 membrane expression correlated with increased nuclear cyclin D1 staining in clinical prostate cancer specimens, and that expression of ErbB-2 was capable of inducing cell cycle progression in human prostate cancer cell lines. We further showed that ErbB-2 induced the cyclin D1 promoter in DU145 cells, and that small interfering RNA knockdown of cyclin D1 protein levels blocked a significant proportion of the heregulin-induced cell cycle progression in LNCaP cells. Probasin promoter-targeted expression of an activated ErbB-2 isoform induced cyclin D1 expression in the mouse prostate, commensurate with prostate intraepithelial neoplasia. Together, these in vitro and in vivo studies identify cyclin D1 as a critical downstream target of ErbB-2 in the prostate epithelium, both of which are possible therapeutic targets for cancer intervention. Furthermore, our novel mouse model provides a useful platform for ongoing in vivo investigations of ErbB-2 signaling in the prostate epithelium.

Drug Insight: role of the androgen receptor in the development and progression of prostate cancer

Functional androgen receptor (AR) signaling is necessary for the development of prostate cancer. The therapeutic effect of androgen deprivation therapy for prostate cancer was described over 60 years ago and this treatment remains the mainstay of systemic therapy despite its transient response duration. It has become clear that AR expression and signaling remains intact as the disease evolves from androgen-sensitive cancer to classically (but perhaps inaccurately) termed hormone refractory prostate cancer. Through several genetic and epigenetic adaptations, prostate tumors continue to rely on AR growth signaling and they thus remain targets of 'hormonal' therapy. The development of new strategies and drugs that can abrogate AR signaling will probably result in important clinical benefits. The biology of androgen independence and the development of new approaches targeting AR signaling are reviewed herein.