Waldenstrom macroglobulinemia cells devoid of BTKC481S or CXCR4WHIM-like mutations acquire resistance to ibrutinib through upregulation of Bcl-2 and AKT resulting in vulnerability towards venetoclax or MK2206 treatment

Abstract

Although ibrutinib is highly effective in Waldenstrom macroglobulinemia (WM), no complete remissions in WM patients treated with ibrutinib have been reported to date. Moreover, ibrutinib-resistant disease is being steadily reported and is associated with dismal clinical outcome (overall survival of 2.9–3.1 months). To understand mechanisms of ibrutinib resistance in WM, we established ibrutinib-resistant in vitro models using validated WM cell lines. Characterization of these models revealed the absence of BTKC481S and CXCR4WHIM-like mutations. BTK-mediated signaling was found to be highly attenuated accompanied by a shift in PI3K/AKT and apoptosis regulation-associated genes/proteins. Cytotoxicity studies using the AKT inhibitor, MK2206±ibrutinib, and the Bcl-2-specific inhibitor, venetoclax±ibrutinib, demonstrated synergistic loss of cell viability when either MK22016 or venetoclax were used in combination with ibrutinib. Our findings demonstrate that induction of ibrutinib resistance in WM cells can arise independent of BTKC481S and CXCR4WHIM-like mutations and sustained pressure from ibrutinib appears to activate compensatory AKT signaling as well as reshuffling of Bcl-2 family proteins for maintenance of cell survival. Combination treatment demonstrated greater (and synergistic) antitumor effect and provides rationale for development of therapeutic strategies encompassing venetoclax+ibrutinib or PI3K/AKT inhibitors+ibrutinib in ibrutinib-resistant WM.

Targeting CD38 with daratumumab is lethal to Waldenström macroglobulinaemia cells

“…The WM cell lines BCWM.1 and RPCI‐WM1 and their isogenic ibrutinib‐resistant (IR) subclones BCWM.1/IR and RPCI‐WM1/IR were used in all experiments. Of note, IR subclones do not harbour BTK C481S or CXCR4 WHIM‐like mutations but are MYD88 L265P positive, as previously described (Paulus et al , ). In some experiments, CD19 + cells from a patient with relapsed and refractory disease and a confirmed diagnosis of WM (WM Patient 11) were used.…”

“…However, pBTK and PLCγ2 were reduced in RPCI‐WM1/IR cells (Fig K, L) and pERK1/2 was lower in BCWM.1/IR cells exposed to the ibrutinib + Dara combination, compared with single‐agent ibrutinib (Fig E, M). We and others have previously shown that IR cells preferentially utilize PI3K/AKT‐associated pathways via transcriptional reprogramming to safeguard against neoplastic growth and survival (Chiron et al , ; Paulus et al , ). Indeed, a significant decrease in pAKT and its downstream effector pS6/S6 was seen in RPCI‐WM1/IR cells treated with ibrutinib + Dara (Fig N, P), but this effect was not evident in BCWM.1/IR cells (Fig F, H).…”

“…Immunoblotting was performed with WM cell lysates, as described previously (Manna et al , ; Paulus et al , ). Antibodies (Cell Signaling Technology, Danvers, MA, USA) against LYN, SYK, BTK, PLCγ2, ERK1/2, AKT, mTOR, S6, and their phosphorylated isoforms were used.…”

Waldenström macroglobulinemia: 2019 update on diagnosis, risk stratification, and management

“…Since macroglobulinemia cells highly express Bcl‐2 venetoclax is a logical therapy for this disorder …”

A Waldenström-macroglobulinaemia és betegségre szabott kezelése

“…A jelenleg WM-ben vizsgálat alatt álló szerek közül az everolimus, a copanlisib és a venetoclax más betegségekben már törzskönyve-zett, így indikáción túl WM-ben történő alkalmazásuk indokolt lehet [5,50]. Elesett általános állapotú, idős betegek palliatív kezelésére a plazmaferézissel kombinált alkilezőszer-monoterápia jó választás lehet.…”