Serum heat shock protein family A member 9 protein as a biomarker for bortezomib resistance and poor prognosis in patients with multiple myeloma.

Bortezomib resistance in multiple myeloma (MM) is a significant clinical challenge that limits the long-term effectiveness. Currently, there is a lack of reliable biomarkers to predict bortezomib resistance. Previous studies reported that several proteins regulate bortezomib resistance through targeting ubiquitin-proteasome pathways, including heat shock protein family A member 9 (HSPA9), dickkopf Wnt signaling pathway inhibitor 1 (DKK1), proteasome 26S subunit non-ATPase 14 (PSMD14), and tripartite motif containing 21 (TRIM21). In our study, we aimed to analyze the expression of these proteins in MM patients and evaluate their potential as biomarkers for bortezomib resistance. Our study enrolled 46 newly diagnosed MM patients (38 bortezomib-sensitive and eight bortezomib-resistant patients) and 52 healthy controls, and serum samples were collected from the patients before initial treatments. The levels of HSPA9, DKK1, PSMD14, and TRIM21 proteins in serum samples were measured using ELISA. The diagnostic power of HSPA9 protein for bortezomib resistance was evaluated through receiver operating characteristic curves combined with the area under curve (AUC). The correlation between HSPA9 protein and clinicopathological features was examined using the chi-square test, and Kaplan-Meier method and Cox regression analysis were applied to assess prognostic value. Compared with healthy controls, increased HSPA9 and DKK1, but decreased TRIM21 protein expression, were observed in serum samples from MM patients. There was no statistical difference in PSMD14 protein expression between the two groups. Notably, compared with bortezomib-sensitive patients, only HSPA9 protein was found to be upregulated in bortezomib-resistant patients, whereas no differences were found in the other proteins. Furthermore, the AUC of serum HSPA9 for differentiating MM patients from healthy controls was 0.906 [95% confidence interval (CI): 0.843-0.968]. And serum HSPA9 expression could effectively differentiate bortezomib-resistant MM patients from bortezomib-sensitive MM patients, with an AUC of 0.845 (95% CI: 0.734-0.957). In addition, elevated serum HSPA9 expression positively correlated with advanced International Staging System stage, increased β2-MG, abnormal immunoglobulin, and bortezomib resistance. Higher serum HSPA9 was linked to shorter overall survival rate and independently predicted poor prognosis. Our study demonstrated that elevated serum HSPA9 protein serves as a potential biomarker for bortezomib resistance and poor prognosis in MM patients.