Heme oxygenase-1 (HO1, Hmox1) degrades excess heme and is considered an anti-oxidative and anti-inflammatory enzyme. Our previous studies in Hmox1 knockout mice revealed the induction of interferon-stimulated genes (ISGs) in all cell types analyzed, despite unchanged interferon production. Here, we sought to determine whether this induction is driven by intrinsic cellular mechanisms or extrinsic cues at the organismal level, and to identify the pathway underlying HO1-dependent ISG regulation. To this end, we analyzed how ISG expression changes in cultured cells exposed to stressors typical of Hmox1 knockout mice. Using murine wild-type and Hmox1-deficient (Hmox1 KO) fibroblasts, we found that under control conditions, the expression of most tested ISGs was independent of cellular HO1 status. We next examined the effects of extrinsic stressors, including hemolytic, oxidative, genotoxic, and replication stress, proinflammatory TNFα, and endogenous heme overload. TNFα, which is upregulated in Hmox1 knockout mice, was the sole and universal inducer of ISGs in both wild-type and Hmox1 KO fibroblasts. Unexpectedly, the response of Hmox1 KO cells to exogenous TNFα was weakened, likely due to impaired NF-κB activity and reduced nuclear retention of the p65 subunit. A similar decrease we observed for STAT1. Additionally, the presence of the TREX1 exonuclease in the nucleus pointed to compromised nuclear envelope integrity in HO-deficient cells. Notably, HO1 colocalizes with PARP1, a protein involved in envelope maintenance and regulation of cytoplasmic-nuclear transport. Inhibition of PARP1 with olaparib dampened TNFα-induced nuclear accumulation of p65 and STAT1 in wild-type cells, but not in Hmox1 KO counterparts. In summary, the inflammation observed in Hmox1-deficient mice appears to be the main cell-extrinsic driver of ISG induction in vivo. Despite this, the inflammatory response to exogenous TNFα is intrinsically attenuated in Hmox1 KO cells, likely due to decreased nuclear retention of NF-κB and STAT1.

Head and neck squamous cell carcinomas (HNSCCs) represent a heterogeneous group of tumors with a complex molecular profile. Despite therapeutic advances, patient prognosis remains poor, emphasizing the need for more effective treatment strategies. Traditional chemotherapy, with cisplatin and 5-fluorouracil (5-FU), remains the gold standard but is limited by toxicity and tumor resistance. Immunotherapy, particularly immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) and its ligand (PD-L1), has improved overall survival, especially in patients with high PD-L1 expression. In parallel, targeted therapies such as poly (ADP-ribose) polymerase 1 (PARP1) inhibitors—which impair DNA repair and increase replication stress—have shown promising activity in HNSCC. Cyclin-dependent kinase (CDK) inhibitors are also under investigation due to their potential to correct dysregulated cell cycle control, a hallmark of HNSCC. This review aims to summarize current and emerging pharmacotherapies for HNSCC, focusing on chemotherapy, immunotherapy, and PARP and CDK inhibitors. It also discusses the evolving role of targeted therapies in improving clinical outcomes. Future research directions include combination therapies, nanotechnology-based delivery systems to enhance treatment specificity, and the development of diagnostic tools such as PARP1-targeted imaging to better guide personalized treatment approaches.

Heme oxygenase-1 (HO1, Hmox1 ) degrades excess heme and is considered an anti-oxidative and anti-inflammatory enzyme. Our previous studies in Hmox1 knockout mice revealed induction of interferon-stimulated genes (ISGs) in all cell types analyzed, despite unchanged interferon production. Here, we sought to identify the pathway underlying HO1-dependent ISG regulation and determine how ISG expression changes in cultured cells in response to stressors typical of Hmox1 -deficient mice. Using murine wild-type and Hmox1 -deficient (KO-Hmox1) fibroblasts, we showed that in cells cultured under control conditions, the expression of most of the tested ISGs was independent of cellular HO1 status. We then analyzed the effect of extrinsic stressors: hemolytic, oxidative, genotoxic, and replication stress, proinflammatory TNFα, and endogenous heme overload. TNFα (upregulated in Hmox1 knockout mice) was the sole and universal ISG inducer in both wild-type and KO-Hmox1 fibroblasts. Unexpectedly, the response of KO-Hmox1 cells to exogenous TNFα was weakened, probably due to impaired NF-κB activity and reduced p65 nuclear retention. A similar decrease we observed for STAT1. Additionally, the presence of TREX1 exonuclease in the nucleus indicated impaired nuclear envelope integrity. Noteworthy, HO1 colocalizes with PARP1, a protein regulating cytoplasmic-nuclear transport. Olaparib-mediated PARP1 inhibition abolished TNAα-induced nuclear accumulation of p65 and STAT1 in wild-type cells, but not in KO-Hmox1 counterparts. In summary, the inflammation typical of Hmox1 -deficient mice appears to be a major inducer of ISGs in vivo . Despite this, the inflammatory response to exogenous TNFα is attenuated in KO-Hmox1 cells, likely due to decreased nuclear retention of NF-κB and STAT1.

Head and neck squamous cell carcinoma (HNSCC) is a therapeutically challenging cancer what underscoring the need for new chemical agents that selectively induce programmed cell death. Fisetin, a naturally occurring flavonoid, exhibits promising anticancer activity but displays limited proapoptotic efficacy and selectivity. Here, we examined whether alkoxylated modification of fisetin enhances its ability to induce apoptosis in HNSCC cells. Fisetin derivatives bearing four-carbon substituents were synthesized and evaluated in multiple HNSCC cell lines. Two derivatives, MKT218 and MKT257, markedly reduced HNSCC cell viability at low micromolar concentrations with low toxicity towards normal human fibroblasts. Notably, the observed cytotoxicity was not associated with activation of a canonical DNA damage response, as neither γH2AX accumulation nor p53 activation was detected. Furthermore, PARP1 cleavage and live-cell imaging combined with annexin V/EthD-III staining revealed a significantly higher proportion of apoptotic cells. The effect was stronger following treatment with MKT218 and MKT257 compared with fisetin. Time-lapse microscopy further demonstrated that fisetin derivatives, particularly MKT218, promote mitosis-associated apoptosis, in contrast to the predominantly cytostatic effect of fisetin. Moreover, in silico docking suggested that MKT218 exerts its pro-apoptotic activity through a multi-target interaction profile involving key regulators of cell survival and apoptosis rather than a single dominant target. To sum up, our findings suggest that alkoxylated fisetin derivatives may be constituted as new non-genotoxic inducers of apoptosis in HNSCC cells.