Chitren, R. | Search bioRxiv

bioRxiv2025

Novel Pan-ALDH Inhibitor KS100 Effectively Targets ALDH+/CD138- Stem-like Cells to Overcome Relapse in Multiple Myeloma

Multiple myeloma (MM), a clonal plasma cell disorder is the second most frequent hematological malignancy in the United States. This malignancy is characterized by a series of symptoms such as bone lesions, hypercalcemia, renal failure, and anemia. The current clinical drugs in the market are successful in treating multiple myeloma patients into remission but does not address relapse where a more aggressive phenotype of the cancer remains untreatable. We hypothesize that a small subset of multiple myeloma stem-like cells (MMSLCs) that overexpress aldehyde dehydrogenases (ALDH+) is the cause of the relapse. Overexpression of ALDH bolsters drug resistance via detoxification and stemness via the retinoic acid signaling pathway. The phenotype of MMSLCs is not yet known for certainty but there are a few well established markers such CD138 negative (CD138neg) cells that are known to overexpress ALDH. In this study, we target regular MM cells and bortezomib resistant ALDH+/CD138neg MMSLCs with a novel, potent, pan-ALDH inhibitor, KS100. Here we report KS100 effectively lowered ALDH expression in regular and bortezomib resistant ALDH+/CD138neg cells, MM cell viability as well as proteins associated with MMSLCs. Most importantly we showed that KS100 lowered ALDH+ populations in regular, bortezomib resistant and CD138neg cells via ALDEFLUOR assay.

molecular biology↗

bioRxiv2022

Development of a Novel Bruton's Tyrosine Kinase Inhibitor that exerts Anti-Cancer Activities Potentiates Response of Chemotherapeutic Agents In Multiple Myeloma Stem Cell-Like Cells

Despite recent improvements in multiple myeloma (MM) treatment, MM remains an incurable disease and most patients experience a relapse. The major reason for myeloma recurrence is the persistent stem cell-like population. It has been demonstrated that overexpression of Brutons tyrosine kinase (BTK) in MM stem cell-like cells is correlated with drug resistance and poor prognosis. We have developed a novel small BTK inhibitor, KS151, which is unique compared to other BTK inhibitors. Unlike ibrutinib, and the other BTK inhibitors such as acalabrutinib, orelabrutinib, and zanubrutinib that covalently bind to the C481 residue in the BTK kinase domain, KS151 can inhibit BTK activities without binding to C481. This feature of KS151 is important because C481 becomes mutated in many patients and causes drug resistance. We demonstrated that KS151 inhibits in vitro BTK kinase activities and is more potent than ibrutinib. Furthermore, by performing a semi-quantitative, sandwich-based array for 71-tyrosine kinase phosphorylation, we found that KS151 specifically inhibits BTK. Our western blotting data showed that KS151 inhibits BTK signaling pathways and is effective against bortezomib-resistant cells as well as MM stem cell-like cells. Moreover, KS151 potentiates the apoptotic response of bortezomib, lenalidomide, and panobinostat in both MM and stem cell-like cells. Interestingly, KS151 inhibits stemness markers and is efficient in inhibiting Nanog and Gli1 stemness markers even when MM cells were co-cultured with bone marrow stromal cells (BMSCs). Overall, our results show that we have developed a novel BTK inhibitor effective against the stem cell-like population, and potentiates the response of chemotherapeutic agents.

molecular biology↗