Cancer immunotherapeutic targeting tropomyosin receptor kinase C (TrkC) through its conjugate and cyclophosphamide

Cancer cells often overexpressed specific receptors to support their proliferation and promote immunosuppressive tumor microenvironment. Tropomyosin receptor kinase C (TrkC) is known to be overexpressed in cancer, and implicated in promoting tumor progression and metastasis. This study investigates synergistic efficacy and immunomodulatory effect of a peptidomimetic TrkC-targeted ligand (IYIY) conjugated with dinitrophenol (DNP) hapten (IYIY-DNP), in combination with cyclophosphamide (CTX), an alkylating chemotherapeutic with immune-modulating properties.

Female BALB/c mice were first immunized with DNP-KLH (Keyhole Limpet Hemocyanin) to elicit anti-DNP antibodies and subsequently implanted with TrkC-expressing murine 4T1 breast carcinoma cells. Tumor-bearing mice received 10 mg/kg IYIY-DNP, 25 mg/kg CTX, or their combination (IYIY-DNP+CTX), on alternating days for five cycles. Tumor growth was monitored for 21 days. On day 10, blood was collected for cytokine profiling, and tumor and lymphoid organs were collected postmortem for immune cells phenotyping.

IYIY-DNP+CTX reduced tumor size by 71.11%, while IYIY-DNP and CTX monotherapy reduced it by 52.97% and 47.23%, respectively. Elevated levels of IL-2, IL-4, IL-6, IL-17A, IL-10, IFN- $\gamma$, and TNF-$\alpha$ while reducing TGF-β, were correlated with regulatory T cells (Tregs) inhibition as observed in IYIY-DNP+CTX. Immune cells phenotyping in tumor-draining lymph nodes (TDLNs), tumor tissues and spleen showed increased antitumor immune cells Th1, Th17 and cytotoxic T lymphocytes, correlating with the inhibition of tumor growth through IYIY-DNP+CTX administration.

IYIY-DNP+CTX significantly reduced TrkC⁺ tumor growth by suppressing immunosuppressive factors and enhancing immune-stimulating responses, helping the immune system fight cancer more effectively.