The **CBX8** gene, encoding Chromobox protein homolog 8, is an important component of the Polycomb repressive complex 1 (PRC1), which plays crucial roles in chromatin remodeling and gene silencing, especially in developmental processes. Here's more detailed information about the gene related to your queries:

### 1. Associated Genes
CBX8 is primarily known for its interaction with other members of the Polycomb group (PcG) proteins, which include:
- **CBX2**: works similarly in the PRC1 complex.
- **RING1B (RING Finger Protein 1)**: essential for the monoubiquitination of histone H2A, a key function of the PRC1 complex.
- **BMI1**: another integral component of PRC1 that also has roles beyond chromatin regulation.
- **EZH2**: while primarily part of the PRC2 complex, it can interact with PRC1 and is involved in histone methylation.
  
Other genes of interest might include activation targets of Polycomb repression including Hox genes and developmental transcription factors.

### 2. Aging and Age-related Diseases
Research indicates that alterations in CBX8 function or expression may contribute to various age-related changes and diseases. Some points of interest include:
- **Cancer**: CBX8 is highlighted as a biomarker for esophagus squamous cell carcinoma and glioblastoma, indicating that aberrant expression might be associated with age-related oncogenesis.
- **Stem Cell Regulation**: Aging can lead to changes in stem cell behavior, and Polycomb group proteins, including CBX8, are critical for maintaining stem cell pluripotency and differentiation potential. Dysregulation of CBX8 might contribute to age-associated decline in tissue regeneration.

### 3. Drug Interactions
While specific small molecules commonly associated with CBX8 are not well established in literature, the broader class of **epigenetic inhibitors** (such as those targeting histone methylation and ubiquitination) may impact its function:
- **EZH2 inhibitors**: As part of the PRC complexes, drugs targeting EPZ-6438 (a small molecule that inhibits EZH2) could indirectly affect the stability and functioning of PRC1, where CBX8 is involved.
- **Histone deacetylase inhibitors (HDACis)**: While primarily affecting histone acetylation, these might modulate the expression of genes under PRC control, including those associated with CBX8.

### 4. Pathways and Biological Processes
CBX8 is involved in numerous key biological pathways and processes, including but not limited to:
- **Negative Regulation of Transcription**: Particularly of developmental genes, through its role in chromatin remodeling.
- **Histone Modification**: Specifically mediating monoubiquitination of histone H2A at Lys-119, leading to changes in chromatin structure and gene accessibility.
- **Developmental Pathways**: It plays a role in establishing and maintaining the identity of various cell lineages, being critical for the regulation of Hox gene clusters that dictate body patterning.

### Conclusion
In summary, the CBX8 gene has essential roles in chromatin dynamics, gene repression through the PRC1 complex, cancer biology, stem cell maintenance, and potentially in age-related biological processes. Interaction with other PcG proteins and involvement in significant pathways emphasize its importance in developmental and disease contexts. Further research may uncover additional complexities linked to its functions and interactions.