XBP1 and Miyoshi myopathy: Comparison of transcriptional profiles of pre-infusion MM with post-infusion MM revealed that residual MM cells showed decreased expression of mature plasma cell genes (such as syndecan-1/SDC1, BCMA/TNFRSF17, and XBP1), but increased expression of the stem-like marker, SOX4, and drug-resistant associated makers, including CD24 (Fig. 1e).