# A tumor-targeted heptamethine cyanine dye induces suppression of progesterone receptor activity to treat hormone receptor-positive breast cancer

## TL;DR

A new tumor-targeted dye effectively treats hormone receptor-positive breast cancer by suppressing progesterone receptors and inducing cell death.

## Contribution

A novel heptamethine cyanine dye, CA800-PR, was developed as a multifunctional antitumor agent for hormone receptor-positive breast cancer.

## Key findings

- CA800-PR suppresses progesterone receptor protein expression and causes Golgi fragmentation in MCF-7 xenograft tumors.
- The dye increases pro-inflammatory M1-type macrophages and induces apoptosis in cancer cells.
- CA800-PR shows potential as an alternative to traditional hormone therapies for breast cancer treatment.

## Abstract

Background: A primary treatment of hormone receptor-positive breast cancer is the pharmacological inhibition of hormone receptors by blocking the effects of estrogen and/or progesterone.

Methods: In MCF-7 xenograft tumors known as estrogen-sensitive breast cancer, a hydrophilic near-infrared (NIR) heptamethine cyanine dye (named CA800-PR) induced Golgi fragmentation and suppressed only progesterone receptor protein expression, regardless of estrogen receptors.

Results: In this study, CA800-PR was newly developed for the treatment of hormone receptor-positive breast cancer unlike conventional drugs such as tamoxifen and aromatase inhibitors. Since the intracellular stress induced by CA800-PR led to the production of pro-inflammatory cytokines, we confirmed a significant increase in the presence of antitumor/pro-inflammatory MHC class II+ CD80+ M1-type macrophages during the course of treatment. Comparing with the traditional hormone therapies aimed at controlling tumor growth or preventing recurrence post-surgery, the tumor-targeted NIR fluorescent dye CA800-PR alone can be effectively used as a multifunctional antitumor agent directly inducing apoptosis in both MCF-7 cells and xenograft tumors.

Conclusion: This work provides a promising alternative to hormone therapy-related breast cancer for future clinical applications.