### BCRP4 Gene Overview
**Gene Symbol:** BCRP4  
**Other Aliases:** BCRP (Breast Cancer Resistance Protein), ABCG2 (ATP-binding cassette sub-family G member 2)

BCRP4 (Breast Cancer Resistance Protein 4) is part of the ABC transporter superfamily and plays a significant role in drug transport and multidrug resistance (MDR) associated with various types of cancers. It is particularly involved in the efflux of xenobiotics, including chemotherapeutic agents, and has implications in pharmacokinetics and tolerance to drugs.

### 1. Associated Genes
While specific associations may not be listed in the provided summaries, BCRP4 is often studied in connection with other ABC transporters, particularly:
- **ABCB1 (MDR1)**: Involved in the efflux of drugs and a common topic of study due to its role in drug resistance.
- **ABCC1 (MRP1)**: Another transporter that works in parallel to ABCG2 in drug excretion.
- **SLC genes**: Various solute carrier genes are sometimes discussed in studies related to BCRP4's interactions with drug uptake and efflux.

### 2. Aging and Age-Related Diseases
Research involving BCRP4 suggests potential connections to aging and age-related diseases:
- **Drug Metabolism**: As aging alters pharmacodynamics and pharmacokinetics, BCRP4 may play a role in how elderly patients respond to medications, contributing to variations in drug effectiveness and toxicity.
- **Cancer**: Since BCRP4 is implicated in breast cancer resistance, it may also influence age-related cancer treatment outcomes.
- **Neurodegenerative Diseases**: There is emerging research suggesting that ABC transporters, including BCRP4, may affect the brain's ability to clear toxic metabolites, which could be linked to conditions such as Alzheimer’s disease.

### 3. Drug Interactions
BCRP4 is known to interact with a variety of drugs, affecting their absorption and distribution:
- **Chemotherapeutic agents**: Such as topotecan and methotrexate, which are substrates for BCRP and may have reduced efficacy in patients with elevated BCRP expression.
- **Cardiovascular drugs**: Drugs such as rosuvastatin have also been noted as substrates for BCRP, influencing their bioavailability.
- **Natural compounds**: Flavonoids and other dietary components may inhibit BCRP activity, modifying the pharmacokinetics of associated drugs.

### 4. Pathways and Biological Processes
BCRP4 is involved in several critical biological processes and pathways:
- **Drug transport:** Actively involved in the efflux of xenobiotic compounds and the regulation of drug disposition.
- **Multidrug resistance:** Plays a significant role in cancer by contributing to the efflux of chemotherapeutics, impacting cancer treatment outcomes.
- **Cellular responses to stress:** BCRP4 may participate in the cellular response to oxidative stress and maintain homeostasis, crucial for cell survival in adverse conditions.
- **Lipids and steroid metabolism:** Involved in the transport of lipid-soluble compounds.

### Conclusion
BCRP4 is an important gene in the context of pharmacology, drug resistance, and potential implications in aging and age-related diseases. Further research is required to fully elucidate the extent of its roles and interactions with drugs and the metabolic pathways it influences.