Photodynamic Therapy with Liposomal Zinc Phthalocyanine and Tirapazamine Increases Tumor Cell Death via DNA Damage

The efficacy of photodynamic therapy (PDT) in some solid tumors is limited by the poor biodistributive properties of conventional photosensitizers and a natural predisposition of tumor cells to survive hypoxia and oxidative stress. This study investigated the therapeutic potential of a third-generation photosensitizer, liposomal zinc phthalocyanine (ZnPC), in combination with the hypoxic cytotoxin tirapazamine (TPZ). TPZ induces DNA double strand breaks (DSBs) under hypoxic conditions and subsequent apoptosis via p53 signaling. Experiments were performed in tumor cells with functional p53 (Sk-Cha1) and dysfunctional p53 (A431). The combination therapy of TPZ and PDT induced DNA DSBs and cell cycle stalling and enhanced the cytotoxicity of PDT by exacerbating apopotic and non-apoptotic tumor cell death. These phenomena occurred regardless of oxygen tension and the mechanism of cell death differed per cell line. Liposomes containing both ZnPC and TPZ exhibited no dark toxicity but were more lethal to both cell types after PDT compared to ZnPC-liposomes lacking TPZ—an effect that was more pronounced under hypoxic conditions. In conclusion, TPZ is a suitable pharmaceutical compound to increase PDT efficacy by exploiting the post-PDT tumor hypoxia. The inclusion of TPZ and ZnPC into a single liposomal delivery system was feasible. The PDT strategy described in this study may be valuable for the treatment of PDT-recalcitrant tumors.

MIR21 Drives Resistance to Heat Shock Protein 90 Inhibition in Cholangiocarcinoma

BACKGROUND & AIMS

Cholangiocarcinomas (CCA) are resistant to chemotherapy, so new therapeutic agents are needed. We performed a screen to identify small-molecule compounds that are active against CCAs. Levels of microRNA 21 (MIR21 or miRNA21) are increased in CCAs. We investigated whether miRNA21 mediates resistance of CCA cells and organoids to HSP90 inhibitors.

METHODS

We performed a high-throughput screen of 484 small-molecule compounds to identify those that reduced viability of 6 human CCA cell lines. We tested the effects of HSP90 inhibitors on cells with disruption of the MIR21 gene, cells incubated with MIR21 inhibitors, and stable cell lines with inducible expression of MIR21. We obtained CCA biopsies from patients, cultured them as organoids (patient-derived organoids). We assessed their architecture, mutation and gene expression patterns, response to compounds in culture, and when grown as subcutaneous xenograft tumors in mice.

RESULTS

Cells with IDH1 and PBRM1 mutations had the highest level of sensitivity to histone deacetylase inhibitors. HSP90 inhibitors were effective in all cell lines, irrespective of mutations. Sensitivity of cells to HSP90 inhibitors correlated inversely with baseline level of MIR21. Disruption of MIR21 increased cell sensitivity to HSP90 inhibitors. CCA cells that expressed transgenic MIR21 were more resistant to HSP90 inhibitors than cells transfected with control vectors; inactivation of MIR21 in these cells restored sensitivity to these agents. MIR21 was shown to target the DnaJ heat shock protein family (Hsp40) member B5 (DNAJB5). Transgenic expression of DNAJB5 in CCA cells that overexpressed MIR21 re-sensitized them to HSP90 inhibitors. Sensitivity of patient-derived organoids to HSP90 inhibitors, in culture and when grown as xenograft tumors in mice, depended on expression of miRNA21.

CONCLUSIONS

miRNA21 appears to mediate resistance of CCA cells to HSP90 inhibitors by reducing levels of DNAJB5. HSP90 inhibitors might be developed for the treatment of CCA and miRNA21 might be a marker of sensitivity to these agents.

INST OX-05-024: first line gemcitabine, oxaliplatin, and erlotinib for primary hepatocellular carcinoma and bile duct cancers: a multicenter Phase II trial

Hepatocellular Carcinoma (HCC) incidence is increasing in the USA. Gemcitabine (G) and oxaliplatin (O) are active in HCC and biliary duct cancer (BDC). Erlotinib (E) is an EGFR tyrosine kinase inhibitor (TKI) with known activity against both. We sought to evaluate the efficacy of the combination G+O+E. Patients with either of the two diagnosis were treated in a phase II trial. Simons 2 stage design was used. A disease‐control rate (DCR), complete response (CR) + partial response (PR)+ stable disease (SD) at 24 weeks of ≤20% and >40% (P0 and P1 of 0.2 and 0.4, respectively) were set as undesirable (null) and desirable results. 26 HCC and 7 BDC patients were accrued. In HCC, 1 PR, 10 SD, and 9 PDs were seen. DCR in HCC was 42%. Among seven (7) patients with BDC, one patient was not evaluable; one achieved a long lasting PR, and five patients had SD and DCR was 86%. Median overall survival (OS) times and progression‐free survivals (PFS) were 196 and 149 days in HCC and 238 days and not reached in BDC. PFS at 26 weeks in HCC was 41% and at 21 weeks in BDC was 60%. Grade 3 toxicities in >5% of patients were fatigue (12.9%), neutropenia (9.6%), thrombocytopenia (9.6%), and diarrhea (6.4%). G+O+E exceeded both preset P0a and P1 of the primary objective with a PFS of 41% at 26 weeks for HCC and preliminary BDC data may warrant further investigations.