Heat shock factor 1 (HSF1-pSer326) predicts response to bortezomib-containing chemotherapy in pediatric AML: a COG report

Abstract

Bortezomib (BTZ) was recently evaluated in a randomized Phase 3 clinical trial which compared standard chemotherapy (cytarabine, daunorubicin, etoposide; ADE) to standard therapy with BTZ (ADEB) for de novo pediatric acute myeloid leukemia. While the study concluded that BTZ did not improve outcome overall, we examined patient subgroups benefitting from BTZ-containing chemotherapy using proteomic analyses. The proteasome inhibitor BTZ disrupts protein homeostasis and activates cytoprotective heat shock responses. We measured total heat shock factor 1 (HSF1) and phosphorylated HSF1 (HSF1-pSer326) in leukemic cells from 483 pediatric patients using Reverse Phase Protein Arrays. HSF1-pSer326 phosphorylation was significantly lower in pediatric AML compared to CD34+ non-malignant cells. We identified a strong correlation between HSF1-pSer326 expression and BTZ sensitivity. BTZ significantly improved outcome of patients with low-HSF1-pSer326 with a 5-year event-free survival of 44% (ADE) vs. 67% for low-HSF1-pSer326 treated with ADEB (P=0.019). To determine the effect of HSF1 expression on BTZ potency in vitro, cell viability with HSF1 gene variants that mimicked phosphorylated (S326A) and non-phosphorylated (S326E) HSF1-pSer326 were examined. Those with increased HSF1 phosphorylation showed clear resistance to BTZ vs. those with wild type or reduced HSF1-phosphorylation. We hypothesize that HSF1-pSer326 expression could identify patients that benefit from BTZ-containing chemotherapy.

Bortezomib is significantly beneficial for de novo pediatric AML patients with low phosphorylation of the NF‐κB subunit RelA

“…Interestingly, low expression of the protein HSF1-pSer 326 , previously found to be associated with the beneficial effect of ADEB in pediatric AML, was among the strongest correlated proteins with low RelA-pSer 536 (r = 0.59, p < 0.001) [11]. Furthermore, twenty-four of the 28 proteins that correlated with RelA-pSer 536 also significantly correlated with HSF1-pSer 326 (Figure S7).…”

“…#3033). Five antibodies were excluded for technical reasons yielding a final of 296 antibodies used for analysis [11]. Stained slides were analyzed using Microvigene Software (version 3.0, Vigene Tech, Carlisle, MA).…”

“…Three hundred forty-eight (85%) patients achieved complete remission by the end of the second course, 31 (8%) patients were refractory or died (failed therapy), 156 (45%) patients relapsed after remission, and 286 were still alive at the end of their follow-up (70%). Survival analysis was performed as published previously [11]. Patients had mutation data available for CEBPA, FLT3-ITD, c-KIT, and NPM1.…”

“…Recently, the Children's Oncology Group (COG) evaluated the efficacy of adding proteasomal inhibition (PI) to standard chemotherapy (ADE: cytarabine (Ara-C), daunorubicin, etoposide) by adding bortezomib (ADEB) in a randomized phase 3 clinical trial for newly diagnosed pediatric AML patients (AAML1031, NCT01371981) [11]. While the study showed no improvement in OS or event-free survival (EFS) across the entire cohort [12], we however, previously showed that ADEB was beneficial in subgroups of patients with decreased phosphorylation of heat shock factor 1 at serine 326 (HSF1-pSer 326 ) [11],…”

Multicenter reverse-phase protein array data integration

“…To date, RPPA technology has been, and is currently being, applied in several cancer clinical trials 11,36 , mostly retrospectively to detect markers of response and resistance [37][38][39][40][41][42][43][44][45] , but in some cases also prospectively to select the most appropriate therapy for a given patient 46,47 . As RPPA technology is readying itself for further implementation in drug development and clinical laboratory settings, there was a demand to evaluate the robustness and reproducibility of RPPA datasets derived from different RPPA platforms.…”