Stromal CYR61 Confers Resistance to Mitoxantrone via Spleen Tyrosine Kinase Activation in Human Acute Myeloid Leukaemia

Abstract

Summary Approximately 50% of children with acute myeloid leukaemia (AML) relapse, despite aggressive chemotherapy. The bone marrow stromal environment protects leukaemia cells from chemotherapy (i.e., stroma-induced chemoresistance), eventually leading to recurrence. Our goal is to delineate the mechanisms underlying stroma-mediated chemoresistance in AML. We used two human bone marrow stromal cell lines, HS-5 and HS-27A, which are equally effective in protecting AML cells from chemotherapy-induced apoptosis in AML-stromal co-cultures. We found that CYR61 was highly expressed by stromal cells, and was upregulated in AML cells by both stromal cell lines. CYR61 is a secreted matricellular protein and is associated with cell-intrinsic chemoresistance in other malignancies. Here, we show that blocking stromal CYR61 activity, by neutralization or RNAi, increased mitoxantrone-induced apoptosis in AML cells in AML-stromal co-cultures, providing functional evidence for its role in stroma-mediated chemoresistance. Further, we found that spleen tyrosine kinase (SYK) mediates CYR61 signalling. Exposure to stroma increased SYK expression and activation in AML cells, and this increase required CYR61. SYK inhibition reduced stroma-dependent mitoxantrone resistance in the presence of CYR61, but not in its absence. Therefore, SYK is downstream of CYR61 and contributes to CYR61-mediated mitoxantrone resistance. The CYR61-SYK pathway represents a potential target for reducing stroma-induced chemoresistance.

Cysteine‐rich protein 61 regulates the chemosensitivity of chronic myeloid leukemia to imatinib mesylate through the nuclear factor kappa B/Bcl‐2 pathway

“…Our results showed that Cyr61 in CML BM decreased the apoptosis of CML cells induced by IM. The findings reported here are consistent with previous reports, in which Cyr61 blocks antitumor drug‐induced apoptosis of cancer cells, resulting in chemotherapy resistance in breast cancer, cervical cancer, and AML . An important observation was that inhibition of Cyr61 restored the chemosensitivity of CML cells to IM in a mouse model of CML.…”

“…Previous studies have shown that Cyr61 decreases the apoptosis induced by anticancer drugs in breast cancer cells, ovarian carcinoma cells, renal cell carcinoma, and AML, suggesting that Cyr61 is linked to chemotherapy resistance in tumors. However, whether Cyr61 is involved in chemoresistance in CML has not been reported.…”

“…Specifically, Cyr61 protects tumor cells from chemo‐induced apoptosis and increases cell survival in solid tumors, such as in breast cancer, ovarian cancer, pancreatic adenocarcinoma, and renal cell carcinoma . Recent studies have indicated that Cyr61 is involved in stroma‐induced chemoresistance in AML . In our previous research, we observed that the levels of Cyr61 were increased in the plasma and BM of patients with acute lymphoblastic leukemia (ALL), and elevated Cyr61 promoted cell survival .…”

Interleukin-6 levels predict event-free survival in pediatric AML and suggest a mechanism of chemotherapy resistance

“…28 Since mitoxantrone is used in current upfront pediatric AML treatment protocols in North America, this finding is potentially clinically significant.…”

“…These results are consistent with our prior finding that environment-induced mitoxantrone resistance is driven primarily by soluble factors as opposed to stromal contact interactions, whereas resistance to etoposide and cytarabine requires contact interactions. 28 When primary AML samples (n 5 7) were treated with IL-6 and sIL-6Ra for 6 hours and then exposed to mitoxantrone for 18 hours, apoptosis was significantly reduced in cultures. A representative patient sample ( Figure 5C) and composite data from the seven tested samples are shown ( Figure 5D).…”