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The CD38 gene is located on human chromosome 4 (4p15.32) and encodes a type II transmembrane glycoprotein with a molecular weight of approximately 45 kDa. Composed of a short intracellular peptide segment, a transmembrane helical domain, and an extracellular catalytic region, the protein exhibits unique bifunctional enzymatic activity: it utilizes nicotinamide adenine dinucleotide (NAD+) as a substrate to generate second messengers such as cyclic ADP-ribose (cADPR), thereby regulating intracellular calcium mobilization; simultaneously, it can hydrolyze cADPR, participating in the homeostasis of nucleotide metabolism. CD38 is widely expressed in the immune system (e.g., B cells, T cells, NK cells, and monocytes) and non-hematopoietic tissues (e.g., heart and pancreas), playing a pivotal role in cell activation, proliferation, and signal transduction.

Under pathological conditions, CD38 serves as a key therapeutic target for various diseases. In the field of hematologic malignancies, CD38 is highly expressed on the surface of cells in multiple myeloma (with 80%–100% of patients testing positive in plasma cells), chronic lymphocytic leukemia, and mantle cell lymphoma, with expression levels inversely correlated with prognosis. Anti-CD38 monoclonal antibodies (such as daratumumab and isatuximab) significantly improve survival outcomes for patients with relapsed/refractory multiple myeloma through mechanisms including complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), and the direct induction of apoptosis.

Figure 1. Recombinant CD38 HEK293 stably expressing CD38.

Cell Resuscitation
1)Rapidly thaw the frozen cells in a 37 °C water bath for approximately 60 seconds. Once thawed (which may take slightly less or more than 60 seconds), immediately transfer the cell suspension from the cryovial into a 15 mL centrifuge tube containing 10 mL of pre-warmed  HEK293 Human CD38 Cell complete culture medium.
2)Centrifuge cells at 1000 rpm for 5 min to remove medium, then resuspend cells in 5 mL of pre-warmed complete medium.
3)Transfer the cell suspension into a T25 culture flask and incubate at 37 °C with 5% CO₂.
4)After approximately 24–36 hours, replace the medium or passage the cells to remove non-adherent dead cells.

Subculturing procedure
1)When the cell density reaches the appropriate confluency for passaging, wash the cells with PBS, then add 1 mL trypsin to detach the cells. When more than 80% of the cells detach upon gently tapping the culture flask, add complete culture medium to terminate digestion. Gently pipette to obtain a single-cell suspension, transfer to a 15 mL centrifuge tube, and centrifuge at 1000 rpm for 5 minutes.

2)Discard supernatant after centrifugation. Resuspend cells in fresh medium to a single-cell suspension and transfer to a new culture flask for continued growth.

Cell Freezing
After trypsinization and centrifugation of cells from each T75 flask or 10 cm culture dish, discard the supernatant. Add 2 mL of cryopreservation medium (90% FBS + 10% DMSO), gently resuspend thoroughly, and aliquot into two cryovials. Immediately place the cryovials into a controlled-rate freezing container (e.g., Nalgene 5100-0001), fill with isopropanol to the indicated level, and store at −80 °C. After 24 hours, transfer the cryovials to liquid nitrogen for long-term storage.