Emerging research in cancer immunometabolism demonstrates that histone H3K18 lactylation plays a profound role in orchestrating immune evasion within thoracic malignancies. Tumor cells frequently undergo aerobic glycolysis, a phenomenon recognized as the Warburg effect. Consequently, this metabolic shift floods the tumor microenvironment with high lactate concentrations. Clinicians historically considered lactate an inert metabolic byproduct. However, contemporary molecular oncology reveals that lactate acts as an active epigenetic signaling molecule that directly modifies histones to regulate gene transcription. In lung cancer, elevated lactate levels drive profound phenotypic adaptations across tumor-infiltrating immune cells. Specifically, lactate reprograms myeloid-derived suppressor cells, transforming them into potent barriers against host antitumor immunity.

How Histone H3K18 Lactylation Rewires the Tumor Microenvironment

Myeloid-derived suppressor cells represent immature myeloid populations that aggressively suppress cytotoxic T lymphocytes and natural killer cells. In pulmonary malignancies, these suppressive cells accumulate within tumor beds and secondary lymphoid tissues. Recent investigations indicate that elevated microenvironmental lactate markedly increases the global protein lactylation profile inside these suppressor cells. Furthermore, researchers identified identical post-translational modifications directly within resected lung cancer patient specimens. This observation underscores the clear clinical relevance of lactylation beyond preclinical animal models. Among diverse histone marks, histone H3K18 lactylation specifically correlates with potent immunosuppression. When lactate enters myeloid cells via monocarboxylate transporters, cellular machinery converts it into lactyl-coenzyme A. Consequently, chromatin-modifying enzymes deposit this lactyl moiety onto lysine 18 of histone H3. In addition, this specific mark remodels chromatin architecture, increasing accessibility at critical transcriptional sites. As a result, myeloid-derived suppressor cells amplify their suppressive programs and paralyze effector T cells, accelerating non-small cell lung cancer progression.

Unpacking the Lactate-CD38-NAD⁺ Metabolic Axis

The primary consequence of histone lactylation in myeloid cells centers on the robust transcriptional upregulation of CD38. CD38 functions as a multifunctional ecto-enzyme possessing potent nicotinamide adenine dinucleotide glycohydrolase activity. Therefore, elevated CD38 expression triggers rapid catalytic degradation of both extracellular and intracellular NAD⁺ pools. Because effector lymphocytes require continuous NAD⁺ supplies to maintain glycolysis and mitochondrial fitness, severe NAD⁺ depletion induces profound metabolic exhaustion. Consequently, cytotoxic CD8⁺ T cells lose their capacity to secrete interferon-gamma and granzyme B. In contrast, myeloid-derived suppressor cells thrive in this depleted niche, maintaining their suppressive dominance. Moreover, CD38 signaling generates adenosine, an immunosuppressive metabolite that further dampens local antitumor immune responses. Preclinical experiments confirm this metabolic interplay. For instance, small interfering RNA knockdown of CD38 abolished the suppressive capability of myeloid-derived suppressor cells. Similarly, pharmacological CD38 inhibition restored vigorous T cell proliferation. Ultimately, the lactate-CD38-NAD⁺ axis represents an indispensable driver of lymphoid metabolic paralysis.

Chromatin Dynamics: Epigenetic Regulators Governing CD38

To decipher how lactylation controls CD38 transcription, molecular profiling focused on the CD38 promoter. Chromatin immunoprecipitation assays revealed that histone H3K18 lactylation concentrates specifically at the CD38 promoter in lung cancer models. Furthermore, researchers identified the precise epigenetic machinery orchestrating this modification. Specifically, the histone acetyltransferase p300 functions as an essential lactyltransferase, transferring lactyl groups onto histone lysine residues. Concurrently, histone deacetylases, particularly HDAC1, HDAC2, and HDAC3, govern delactylation dynamics. In addition, the bromodomain and extraterminal domain family member BRD4 acts as a critical epigenetic reader. BRD4 recognizes lactylated lysine sites and recruits transcriptional elongation factors directly to the CD38 promoter. Thus, p300, HDAC1-3, and BRD4 work in concert to coordinate CD38 transcription during microenvironmental lactate fluctuations. When scientists disrupt these regulatory nodes, CD38 expression drops substantially. Therefore, targeting the interplay between chromatin writers, erasers, and readers offers a compelling molecular strategy to intercept aberrant myeloid cell activation in lung cancer.

Therapeutic Implications for Lung Cancer Immunotherapy

Immune checkpoint inhibitors have revolutionized modern oncology, yet primary resistance continues to challenge clinicians managing advanced lung cancer. Abundant intratumoral myeloid-derived suppressor cells strongly correlate with immunotherapy failure and reduced overall survival. Because these suppressive cells rely heavily on the lactate-CD38-NAD⁺ axis, disrupting this pathway provides an innovative blueprint for combinatorial therapy. In experimental lung cancer models, treating tumor-bearing mice with selective CD38 inhibitors significantly delayed malignant tumor progression. Moreover, targeting CD38 restored local NAD⁺ concentrations, thereby reviving exhausted cytotoxic T lymphocytes. In clinical practice, anti-CD38 monoclonal antibodies such as daratumumab and isatuximab already possess regulatory approvals for hematological malignancies. Consequently, translating these existing therapeutic agents into solid tumor protocols represents an exciting clinical opportunity. Furthermore, combining CD38 blockade with programmed cell death protein 1 inhibitors could dismantle immune tolerance from two complementary angles. Thus, targeting this metabolic-epigenetic axis holds immense promise for overcoming treatment recalcitrance in lung cancer.

Future Clinical Horizons and Translational Potential

Translating these fundamental discoveries into oncology practice requires systematic validation across clinical cohorts. First, oncologists must evaluate whether circulating or intratumoral histone H3K18 lactylation levels serve as reliable predictive biomarkers for treatment response. In addition, measuring CD38 expression on peripheral myeloid-derived suppressor cells could identify patients susceptible to immunotherapy resistance. Such non-invasive liquid biopsy strategies would enable precise patient stratification in non-small cell lung cancer. Furthermore, researchers must explore small-molecule inhibitors that selectively disrupt p300 lactyltransferase activity without impairing essential physiological acetylation. Similarly, developing targeted delactylase modulators could offer unprecedented epigenetic precision. Notably, clinical oncologists should also investigate strategies that diminish systemic and local lactate accumulation. For example, lactate dehydrogenase inhibitors or monocarboxylate transporter blockers could starve myeloid suppressor cells of their epigenetic substrate. Ultimately, unraveling the metabolic dialogue between cancer cells and the stroma will illuminate novel avenues for intervention. As translational trials advance, dual targeting of metabolic reprogramming and epigenetic modifications will transform lung cancer management.

What is histone H3K18 lactylation and why is it important in cancer?

Histone H3K18 lactylation is a metabolic-epigenetic modification where lactate-derived lactyl groups attach to lysine 18 of histone H3 proteins. In cancer biology, this mark couples cellular glycolysis directly to gene transcription within the tumor microenvironment. Consequently, it stimulates the expression of immunosuppressive genes in myeloid-derived suppressor cells and malignant cells. Ultimately, this epigenetic alteration promotes immune evasion, accelerates disease progression, and dampens the efficacy of conventional immune checkpoint therapies in lung cancer patients.

How does CD38 expression in MDSCs suppress antitumor immunity?

CD38 functions as a robust ecto-enzyme that aggressively consumes and hydrolyzes nicotinamide adenine dinucleotide (NAD⁺). When myeloid-derived suppressor cells upregulate CD38, they rapidly deplete extracellular and intracellular NAD⁺ within the surrounding tumor microenvironment. Because cytotoxic T lymphocytes and natural killer cells require abundant NAD⁺ to sustain their metabolic fitness and effector functions, this profound depletion causes severe immune paralysis. Therefore, effector lymphocytes fail to mount effective cytotoxic responses against lung cancer cells.

Can existing CD38 inhibitors be repurposed for lung cancer treatment?

Yes, approved CD38 inhibitors like daratumumab and isatuximab, currently standard in multiple myeloma, represent promising candidates for repurposing. Preclinical evidence shows that CD38 blockade preserves NAD⁺ levels, reduces myeloid suppressor cell activity, and delays lung tumor progression. Furthermore, combining CD38 inhibition with PD-1 or PD-L1 immune checkpoint blockers may overcome primary immunotherapy resistance. Consequently, oncologists anticipate that upcoming clinical trials will actively test these rational combination regimens in patients with advanced non-small cell lung cancer.

Disclaimer: This content is for informational and educational purposes only... Refer to the latest local and national guidelines for clinical practice.

References

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