Cancer-associated fibroblasts (CAFs) are an important component of the tumor microenvironment. The most common notion in the CAF research field has been that CAFs promote cancer progression through various mechanisms. Interestingly, however, recent studies have revealed that CAFs are heterogeneous and that CAF subsets that suppress cancer progression (cancer-restraining CAFs [rCAFs]) must exist in addition to well-characterized cancer-promoting CAFs (pCAFs). However, the identity and specific markers of rCAFs have not been reported.~The investigators recently identified Meflin as a specific marker protein of rCAFs in pancreatic and colon cancers. The investigator's studies revealed that rCAFs are similar to a small subset of resident fibroblasts, which is consistent with the famous hypothesis proposed by Micheal Stoker (University of Glasgow) more than 50 years ago, stating that static normal fibroblasts suppress tumor growth. Interestingly, The investigator's lineage tracing experiments showed that Meflin-positive rCAFs differentiate into Meflin-negative pCAFs during cancer progression. These studies revealed that the tumor stroma is comprised of pCAFs and rCAFs, which is analogous to the heterogeneity of tumor-infiltrating immune cells (e.g., protumor regulatory T cells versus antitumor cytotoxic T cells).~The identification of the rCAF marker Meflin enabled the investigators to develop new strategies to convert or reprogram pCAFs to rCAFs. Using a pharmacological approach, The investigators performed a chemical library screen and identified Am80, a synthetic unnatural retinoid, as a reagent that effectively converts Meflin-negative pCAFs to Meflin-positive rCAFs. Am80 administration improved the sensitivity of pancreatic cancer to chemotherapeutics. These data suggested that the conversion of pCAF to rCAFs may represent a new strategy for pancreatic cancer treatment.~The object of this study is to perform an investigator-initiated clinical study to investigate the effect of AM80 on pancreatic cancer with a combination of conventional tumoricidal agents including gemcitabine and nab-paclitaxel.
To evaluate the safety and tolerability of Am80（Generic name: Tamibarotene, Development code: MIKE-1） in combination with gemcitabine (GEM) and nab-paclitaxel (nab-PTX) in patients with unresectable pancreatic cancer and to determine the recommended dose. Efficacy will also be exploratively investigated.