Regulation of Fibroblast Activation Protein-α Expression: Focus on Intracellular Protein Interactions

The prolyl-specific peptidase fibroblast activation protein-α (FAP-α) is expressed at very low or undetectable levels in nondiseased human tissues but is selectively induced in activated (myo)fibroblasts at sites of tissue remodeling in fibrogenic processes. In normal regenerative processes involving transient fibrosis FAP-α⁺(myo)fibroblasts disappear from injured tissues, replaced by cells with a normal FAP-α^- phenotype. In chronic uncontrolled pathological fibrosis FAP-α⁺(myo)fibroblasts permanently replace normal tissues. The mechanisms of regulation and elimination of FAP-α expression in(myo)fibroblasts are unknown. According to a yeast two-hybrid screen and protein databanks search, we propose that the intracellular (co)-chaperone BAG6/BAT3 can interact with FAP-α, mediated by the BAG6/BAT3 Pro-rich domain, inducing proteosomal degradation of FAP-α protein under tissue homeostasis. In this Perspective, we discuss our findings in the context of current knowledge on the regulation of FAP-α expression and comment potential therapeutic strategies for uncontrolled fibrosis, including small molecule degraders (PROTACs)-modified FAP-α targeted inhibitors.

The GYMSSA trial: a prospective randomized trial comparing gastrectomy, metastasectomy plus systemic therapy versus systemic therapy alone

BACKGROUND

The standard of care for metastatic gastric cancer (MGC) is systemic chemotherapy which leads to a median survival of 6-15 months. Survival beyond 3 years is rare. For selected groups of patients with limited MGC, retrospective studies have shown improved overall survival following gastrectomy and metastasectomies including peritoneal stripping with continuous hyperthermic peritoneal perfusion (CHPP), liver resection, and pulmonary resection. Median survival after liver resection for MGC is up to 34 months, with a five year survival rate of 24.5%. Similarly, reported median survival after pulmonary resection of MGC is 21 months with long term survival of greater than 5 years a possibility. Several case reports and small studies have documented evidence of long-term survival in select individuals who undergo CHPP for MGC.

DESIGN

The GYMSSA trial is a prospective randomized trial for patients with MGC. It is designed to compare two therapeutic approaches: gastrectomy with metastasectomy plus systemic chemotherapy (GYMS) versus systemic chemotherapy alone (SA). Systemic therapy will be composed of the FOLFOXIRI regimen. The aim of the study is to evaluate overall survival and potential selection criteria to determine those patients who may benefit from surgery plus systemic therapy. The study will be conducted by the Surgery Branch at the National Cancer Institute (NCI), National Institutes of Health (NIH) in Bethesda, Maryland. Surgeries and followup will be done at the NCI, and chemotherapy will be given by either the local oncologist or the medical oncology branch at NCI.

TRIAL REGISTRATION

ClinicalTrials.gov ID. NCT00941655.

Photodynamic molecular beacon triggered by fibroblast activation protein on cancer-associated fibroblasts for diagnosis and treatment of epithelial cancers

Fibroblast activation protein (FAP) is a cell-surface serine protease highly expressed on cancer-associated fibroblasts of human epithelial carcinomas but not on normal fibroblasts, normal tissues, and cancer cells. We report herein a novel FAP-triggered photodynamic molecular beacon (FAP-PPB) comprising a fluorescent photosensitizer and a black hole quencher 3 linked by a peptide sequence (TSGPNQEQK) specific to FAP. FAP-PPB was effectively cleaved by both human FAP and murine FAP. By use of the HEK293 transfected cells (HEK-mFAP, FAP(+); HEK-vector, FAP(-)), systematic in vitro and in vivo experiments validated the FAP-specific activation of FAP-PPB in cancer cells and mouse xenografts, respectively. FAP-PPB was cleaved by FAP, allowing fluorescence restoration in FAP-expressing cells while leaving non-expressing FAP cells undetectable. Moreover, FAP-PPB showed FAP-specific photocytotoxicity toward HEK-mFAP cells whereas it was non-cytotoxic toward HEK-Vector cells. This study suggests that the FAP-PPB is a potentially useful tool for epithelial cancer detection and treatment.

First-line treatment of advanced gastric cancer and hepatic dysfunction with oxaliplatin, 5-fluorouracil and cetuximab

There is no standard chemotherapy regimen in advanced gastric cancer with poor performance status and hepatic dysfunction. New chemotherapeutical agents and targeted therapy have demonstrated promising results in terms of efficacy and safety in phase II clinical trials. We report the case of a 68-year-old man with stage IV gastric cancer and severe hepatic dysfunction due to liver metastases treated with a combination of oxaliplatin, 5-fluorouracil and cetuximab.

Capecitabine in advanced gastric cancer

Since the routine introduction of chemotherapy for advanced gastric cancer in the early 1990 s, median survival for gastric cancer has improved from 3 months, with best supportive care alone, to > 11 months in recently reported Phase III trials of triplet chemotherapy. Capecitabine is an orally-active fluoropyrimidine, which is selectively metabolised to fluorouracil in tumour cells. The combinations of platinum compounds and capecitabine have been evaluated in two recent, large, Phase III trials demonstrating non-inferiority in efficacy compared with platinum plus continuous infusion fluorouracil. In view of the convenience and flexibility of patients in adjusting dosage when encountering toxicities, capecitabine is replacing continuous infusion fluorouracil as the backbone of combination chemotherapy in advanced gastric cancer patients. Future trials evaluating biologicals are now incorporating capecitabine combinations as control arms in both advanced disease and peri-operative settings in gastric cancer.

Talabostat

Talabostat mesilate is an orally active, specific inhibitor of dipeptidyl peptidases, including tumor-associated fibroblast activation protein. However, by an independent mechanism, talabostat also stimulates the upregulation of cytokines and chemokines to engender a tumor-specific host immune response, thus giving it a unique dual mechanism of action. In clinical trials, talabostat has demonstrated significant activity, including achieving complete responses in patients with non-small-cell lung cancer and malignant melanoma.