Arabinofuranosylcytosine (BioDeep_00000176170)

描述信息

Isolated from the mushroom Xerocomus nigromaculatus of unknown palatability

This compound has been identified in human blood as reported by (PMID: 31557052 ). Arabinofuranosylcytosine is not a naturally occurring metabolite and is only found in those individuals exposed to this compound or its derivatives. Technically Arabinofuranosylcytosine is part of the human exposome. The exposome can be defined as the collection of all the exposures of an individual in a lifetime and how those exposures relate to health. An individual's exposure begins before birth and includes insults from environmental and occupational sources.

Arabinofuranosylcytosine (Ara-C), also known as cytarabine, is a chemotherapeutic agent that is widely used in the treatment of various types of cancer, particularly hematological malignancies such as acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). The biological functions of Ara-C are primarily related to its antineoplastic properties, which are derived from its mechanism of action within the cell. Here is a detailed description of its biological functions:
1. **Inhibition of DNA Synthesis**: Ara-C functions as a nucleoside analog, which means it resembles the natural building blocks of DNA. Once inside the cell, Ara-C is converted to its active metabolite, araCTP (arabinofuranosylcytosine triphosphate). AraCTP competes with the natural deoxycytidine triphosphate (dCTP) for incorporation into the growing DNA chain during the S phase of the cell cycle. Because Ara-C lacks a 3'-hydroxyl group, its incorporation into DNA leads to chain termination, effectively stopping DNA synthesis.
2. **Cell Cycle Specificity**: Ara-C is most effective against cells that are actively dividing. Since it targets cells in the S phase of the cell cycle, it is particularly harmful to rapidly dividing cancer cells, which often spend a significant portion of their cycle in this phase.
3. **Inhibition of DNA Repair**: Beyond its direct effect on DNA synthesis, Ara-C can also interfere with DNA repair mechanisms. This is because the incorporation of Ara-C into DNA can cause mispairing and induce DNA damage, which the cell may be unable to repair properly.
4. **Cell Death Induction**: The inhibition of DNA synthesis and the induction of DNA damage can lead to cell death through apoptosis or necrosis. Cells that cannot replicate their DNA or repair the damage caused by Ara-C activation are programmed to die, which is a desirable outcome in the context of cancer treatment.
5. **Immune System Modulation**: In some cases, Ara-C can also modulate the immune system, although this is not its primary function. It can affect the function and proliferation of immune cells, which can have implications for both its therapeutic effects and side effects.
6. **Enzymatic Conversion**: Ara-C must be activated within the cell by the enzyme deoxycytidine kinase (dCK), which phosphorylates it to Ara-CMP (monophosphate), then to Ara-CDP (diphosphate), and finally to Ara-CTP. The efficiency of this conversion can vary between different types of cancer cells and normal cells, contributing to the selectivity of Ara-C's action.
7. **Cross-Linking Potential**: Although less common, Ara-C can also form cross-links with DNA, further complicating DNA structure and function, which can contribute to its cytotoxic effects.
The biological functions of Ara-C are complex and can vary depending on the dose, the specific cancer type, and the individual patient's metabolism. Its use is carefully monitored in clinical settings due to its potential for significant side effects, including myelosuppression (decreased production of blood cells), gastrointestinal toxicity, and central nervous system toxicity.

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