By analyzing various single-cell datasets from different cancer types, we obtained insights into the expression patterns of HTR1D (Figure 7A), HTR1E (Figure S7A), HTR1F (Figure 7C), HTR2A (Figure S7B), HTR2B (Figure 7B), HTR4 (Figure S7C), HTR5BP (Figure S7D), HTR6 (Figure S7E), and HTR7 (Figure 7D) at the single-cell level. The gene discussed is HTR1D; the disease is cancer.