EXPRESS: Amino Acid Transporter SLC38A3 Mediates Bone Cancer Pain in Rats Via the PI3K/AKT/TRPV1 Signaling Pathway

Bone cancer pain (BCP), one of the most intractable symptoms in patients with cancer, remains poorly understood and lacks effective therapeutic interventions. In this study, we employed an established rat model of BCP induced by intratibial injection of MRMT-1 mammary carcinoma cells. Transcriptomic profiling of the L4-L6 dorsal root ganglia (DRGs) revealed an upregulation of the amino acid transporter SLC38A3. This finding was further confirmed by time-dependent increases in both its mRNA and protein levels. Immunofluorescence co-localization indicated that SLC38A3 was expressed in NF200-, CGRP-, and IB4-positive neurons within the L4-L6 DRGs, and its expression was upregulated in the BCP model. Concomitantly, the transient receptor potential vanilloid 1 (TRPV1) expression in BCP rat DRGs was dynamically upregulated at both the mRNA and protein levels, aligning temporally with pain hypersensitivity. Lentivirus-mediated overexpression or knockdown of SLC38A3 in the DRGs led to a corresponding upregulation or downregulation of TRPV1-expression. Activation of the PI3K/AKT signaling pathway corresponds with BCP-related pain behaviors and expression patterns of SLC38A3 and TRPV1. Bexarotene alleviates BCP in rats by suppressing the aberrant overexpression of SLC38A3, thereby blocking the PI3K/AKT signaling pathway-mediated upregulation of TRPV1. These findings indicate that SLC38A3, through its downstream PI3K/AKT-TRPV1 axis, may serve as a potential molecular mechanism for analgesia in BCP.