Winfried H. Alsdorf

The marine triterpene glycoside frondoside A exhibits activity in vitro and in vivo in prostate cancer.

Despite recent advances in the treatment of metastatic castration‐resistant prostate cancer (CRPC), outcome of patients remains poor due to the development of drug resistance. Thus, new drugs are urgently needed. We investigated efficacy, toxicity and mechanism of action of marine triterpene glycoside frondoside A (FrA) using CRPC cell lines in vitro and in vivo. FrA revealed high efficacy in human prostate cancer cells, while non‐malignant cells were less sensitive. Remarkably, proliferation and colony formation of cells resistant to enzalutamide and abiraterone (due to the androgen receptor splice variant AR‐V7) were also significantly inhibited by FrA. The marine compound caused cell type specific cell cycle arrest and induction of caspase‐dependent or ‐independent apoptosis. Up‐regulation or induction of several pro‐apoptotic proteins (Bax, Bad, PTEN), cleavage of PARP and caspase‐3 and down‐regulation of anti‐apoptotic proteins (survivin and Bcl‐2) were detected in treated cells. Global proteome analysis revealed regulation of proteins involved in formation of metastases, tumor cell invasion, and apoptosis, like keratin 81, CrkII, IL‐1β and cathepsin B. Inhibition of pro‐survival autophagy was observed following FrA exposure. In vivo, FrA inhibited tumor growth of PC‐3 and DU145 cells with a notable reduction of lung metastasis, as well as circulating tumor cells in the peripheral blood. Increased lymphocyte counts of treated animals might indicate an immune modulating effect of FrA. In conclusion, our results suggest that FrA is a promising new drug for the treatment of mCRPC. Induction of apoptosis, inhibition of pro‐survival autophagy, and immune modulatory effects are suspected modes of actions.

In Situ Detection and Quantification of AR-V7, AR-FL, PSA, and KRAS Point Mutations in Circulating Tumor Cells

BACKGROUND Liquid biopsies can be used in castration-resistant prostate cancer (CRPC) to detect androgen receptor splice variant 7 (AR-V7), a splicing product of the androgen receptor. Patients with AR-V7-positive circulating tumor cells (CTCs) have greater benefit of taxane chemotherapy compared with novel hormonal therapies, indicating a treatment-selection biomarker. Likewise, in those with pancreatic cancer (PaCa), KRAS mutations act as prognostic biomarkers. Thus, there is an urgent need for technology investigating the expression and mutation status of CTCs. Here, we report an approach that adds AR-V7 or KRAS status to CTC enumeration, compatible with multiple CTC-isolation platforms. METHODS We studied 3 independent CTC-isolation devices (CellCollector, Parsortix, CellSearch) for the evaluation of AR-V7 or KRAS status of CTCs with in situ padlock probe technology. Padlock probes allow highly specific detection and visualization of transcripts on a cellular level. We applied padlock probes for detecting AR-V7, androgen receptor full length (AR-FL), and prostate-specific antigen (PSA) in CRPC and KRAS wild-type (wt) and mutant (mut) transcripts in PaCa in CTCs from 46 patients. RESULTS In situ analysis showed that 71% (22 of 31) of CRPC patients had detectable AR-V7 expression ranging from low to high expression [1-76 rolling circle products (RCPs)/CTC]. In PaCa patients, 40% (6 of 15) had KRAS mut expressing CTCs with 1 to 8 RCPs/CTC. In situ padlock probe analysis revealed CTCs with no detectable cytokeratin expression but positivity for AR-V7 or KRAS mut transcripts. CONCLUSIONS Padlock probe technology enables quantification of AR-V7, AR-FL, PSA, and KRAS mut/wt transcripts in CTCs. The technology is easily applicable in routine laboratories and compatible with multiple CTC-isolation devices.

Marine compound rhizochalinin shows high in vitro and in vivo efficacy in castration resistant prostate cancer.

Development of drug resistance is an inevitable phenomenon in castration-resistant prostate cancer (CRPC) cells requiring novel therapeutic approaches. In this study, efficacy and toxicity of Rhizochalinin (Rhiz) – a novel sphingolipid-like marine compound – was evaluated in prostate cancer models, resistant to currently approved standard therapies. In vitro activity and mechanism of action of Rhiz were examined in the human prostate cancer cell lines PC-3, DU145, LNCaP, 22Rv1, and VCaP. Rhiz significantly reduced cell viability at low micromolar concentrations showing most pronounced effects in enzalutamide and abiraterone resistant AR-V7 positive cells. Caspase-dependent apoptosis, inhibition of pro-survival autophagy, downregulation of AR-V7, PSA and IGF-1 expression as well as inhibition of voltage-gated potassium channels were identified as mechanisms of action. Remarkably, Rhiz re-sensitized AR-V7 positive cells to enzalutamide and increased efficacy of taxanes. In vivo activity and toxicity were evaluated in PC-3 and 22Rv1 NOD SCID mouse xenograft models using i.p. administration. Rhiz significantly reduced growth of PC-3 and 22Rv1 tumor xenografts by 27.0% (p = 0.0156) and 46.8% (p = 0.047) compared with controls with an increased fraction of tumor cells showing apoptosis secondary to Rhiz exposure. In line with the in vitro data, Rhiz was most active in AR-V7 positive xenografts in vivo. In animals, no severe side effects were observed. In conclusion, Rhiz is a promising novel marine-derived compound characterized by a unique combination of anticancer properties. Its further clinical development is of high impact for patients suffering from drug resistant prostate cancer especially those harboring AR-V7 mediated resistance to enzalutamide and abiraterone.

Proteomic-based investigations on the mode of action of the marine anticancer compound rhizochalinin

Rhizochalinin (Rhiz) is a novel marine natural sphingolipid‐like compound, which shows promising in vitro and in vivo activity in human castration‐resistant prostate cancer. In the present study, a global proteome screening approach was applied to investigate molecular targets and biological processes affected by Rhiz in castration‐resistant prostate cancer. Bioinformatical analysis of the data predicted an antimigratory effect of Rhiz on cancer cells. Validation of proteins involved in the cancer‐associated processes, including cell migration and invasion, revealed downregulation of specific isoforms of stathmin and LASP1, as well as upregulation of Grp75, keratin 81, and precursor IL‐1β by Rhiz. Functional analyses confirmed an antimigratory effect of Rhiz in PC‐3 cells. Additionally, predicted ERK1/2 activation was confirmed by Western blotting analysis, and revealed prosurvival effects in Rhiz‐treated prostate cancer cells indicating a potential mechanism of resistance. A combination of Rhiz with MEK/ERK inhibitors PD98059 (non‐ATP competitive MEK1 inhibitor) and FR180204 (ATP‐competitive ERK1/2 inhibitor) resulted in synergistic effects. This work provides further insights into the molecular mechanisms underlying Rhiz bioactivity. Furthermore, our research is exemplary for the ability of proteomics to predict drug targets and mode of action of natural anticancer agents.

Frondoside A induces AIF-associated caspase-independent apoptosis in Burkitt lymphoma cells

Abstract For patients with refractory or relapsed Burkitt lymphoma (BL), no standard therapy is available for second-line treatment to date. Nonfunctional caspases-dependent apoptosis pathways, inactivating p53 mutations and pro-survival autophagy prevent activity of conventional chemotherapy. Thus, new drugs bypassing these mechanisms of resistance are required. Here, we investigated the efficacy of the marine natural compound frondoside A (FrA) in eight BL cell lines. FrA revealed cytotoxic effects in all cell lines tested including the multiresistant CA46 cells. Remarkably, FrA induced caspases- and p53-independent apoptosis, which was characterized by decreased expression of antiapoptotic survivin and Bcl-2, mitochondria targeting (release of cytochrome C, HtrA2/Omi and the apoptosis-inducing factor (AIF), and altered production of ROS) and translocation of AIF to the nuclei. In addition, signs of inhibition of pro-survival autophagy were observed. Thus, FrA is a promising candidate for the treatment of refractory or relapsed BL revealing resistances to standard therapies.

Treatment of Metastatic Spindle Epithelial Tumor with Thymus-Like Differentiation (SETTLE) - Long-Term Disease Control by Multimodal Therapy

Background: Spindle epithelial tumor with thymus-like differentiation (SETTLE) is a very rare tumor that occurs mainly in pediatric patients and young adults. Only few of these patients develops metastatic disease; therefore, clinical data regarding treatment and outcome of metastatic SETTLE are extremely limited. Several chemotherapy agents have been used in SETTLE but due to the limited number of patients no evidence-based therapy exists. Case Report: We present a case of metastatic SETTLE presenting with high tumor burden and paraneoplastic hypercalcemia. Prolonged disease control with several lines of platinum-based chemotherapy, anti-epidermal growth factor receptor therapy and additional radiotherapy was achieved. Conclusion: Multi-agent chemotherapy is an active treatment in metastatic SETTLE and can induce sustained tumor control.

Severe and irreversible myelopathy after concurrent systemic and intrathecal nucleoside analogue treatment for refractory diffuse large B-cell lymphoma: A case report and review of the literature

We report a patient with refractory diffuse large B-cell lymphoma who developed irreversible, severe spinal neurotoxicity after concurrent treatment with intrathecal and systemic cytarabine. Shortly after concomitant administration of intrathecal triple therapy (MTX, dexamethasone and cytarabine) and high-dose systemic cytarabin (R-DHAP protocol) the patient lost control of bowel and bladder function and developed an ascending, irreversible paraplegia. Infectious or neoplastic diseases of the spinal cord were ruled out. A magnetic resonance imaging scan of the spine resulted in a diagnosis of toxic myelitis. Previously observed cases of spinal neurotoxicity after cytarabine treatment are reviewed as well as current guidelines for the use of intrathecal chemotherapy in high-grade non-Hodgkin lymphoma. In summary, severe spinal neurotoxicity of intrathecal chemotherapy is a rare side-effect, however several studies suggest that the neurotoxicity of cytarabine is significantly enhanced by concurrent intrathecal and high-dose systemic administration. Simultaneous high-dose systemic and intrathecal chemotherapy with cytarabine should therefore be avoided.