ERK Activity in Immature Leukemic Cells Drives Clonal Selection during Induction Therapy for Acute Myeloid Leukemia

Abstract

Selection of resistant clones following intensive chemotherapy is a common obstacle for cure in many cancers, particularly in acute myeloid leukemia (AML). In AML, clone-specific sensitivity to chemotherapy varies even within the same patient. Multiple mutations and genetic aberrations are associated with clones surviving chemotherapy. The current study explored the role of activated signaling pathways in chemoresistance as a function of cell maturation, reflected by CD34 expression. In-vitro, Kasumi-1 leukemic cell line, sorted by CD34 expression, showed increased apoptosis only in the CD34− subpopulation after exposure to cytosine arabinoside (Ara-C) or daunorubicin. The resistant CD34+ subset demonstrated higher expression of ERK1/2 and BCL-2 proteins than CD34− cells. MEK1/2 inhibition elevated Ara-C ability to induce apoptosis in CD34+ cells, suggesting that MEK1/2-ERK1/2 is surviving signaling, which correlates to cell maturation levels and plays a role in chemoresistance. Deep sequencing of sorted CD34+/− populations, both derived from the same patient samples, demonstrated various subclonal distribution of NPM1, DNMT3A and FLT3-ITD mutations. Interestingly, in these samples, p-ERK levels and apoptosis rates following chemotherapy exposure significantly differed between CD34+/− populations. Hence, clones may be selected due to their ability to escape apoptosis rather than a direct effect of chemotherapy on a specific mutated clone.

Early response evaluation by single cell signaling profiling in acute myeloid leukemia

“…7f ). The ERK pathway has been shown to drive the selection of resistant clones during induction therapy for AML in vitro and elevated ERK1/2 activity has also been observed in AML patients who have developed resistance to FLT3-targeted inhibitors 27 , 28 . Expression of p38 has also been shown to drive chemotherapy resistance in different cancers 29 , 30 .…”

Midostaurin in combination with chemotherapy is most effective in patients with acute myeloid leukemia presenting with high FLT3‐ITD allelic ratio who proceed to allogeneic stem cell transplantation while in first complete remission

“…In a recent in vitro study, 17 midostaurin has been reported to inhibit several signaling pathways, including the ERK pathway. Our previous study has demonstrated a critical role of ERK activation in clonal selection and enhancement of chemo‐sensitivity by direct ERK inhibition 18 . The efficacy of midostaurin in high‐AR cases may therefore be attributed to co‐inhibition of FLT3, at the receptor level, and of downstream kinases like ERK.…”

Early response evaluation by single cell signaling profiling in acute myeloid leukemia

“…p-ERK1/2 has previously been shown to be upregulated in CD34+ cells compared CD34cells. 31 10 patients had CD34+ cells in MC9, most of them (7/10) were in the high 24h-p-ERK1/2 group (Supplementary Fig. 9b).…”

“…29,30 The ERK pathway has been shown to drive selection of resistant clones during induction therapy for AML in vitro and elevated ERK1/2 activity has also been observed in AML patients who have developed resistance to FLT3-targeted inhibitors. 31,32 Expression of p38 has also been shown to drive chemotherapy resistance in different cancers. 33,34 Similarly, the high ERK 1/2 and p38 activation level following chemotherapy treatment could indicate an enhanced pro-survival signaling response in the peripheral blood leukemic blasts.…”