Hiroki Kuniyasu

Oncology Letters is an international journal devoted to Experimental and Clinical Oncology.

Following the publication of the above paper, an interested reader has drawn the Editor's attention to the fact that the tubulin control blots featured in Fig. 3 on p. 88 were strikingly similar to the control blots subsequently featured in a figure in another paper that was published by the same research group in the journal Oncotarget, where the experimental conditions were reported to be different. A subsequent investigation of the data in this paper undertaken by the Editorial Office revealed that various of the western blots included in Figs. 2A and B, 3E and F, and 4C and D appeared to have been duplicated within and/or between these figure parts; moreover, various of the data in these figure parts were remarkably similar to data which appeared (either previously or subsequently relative to the publication date of this article) in other papers written by different authors at different research institutes. Given that the contentious data mentioned above have apparently re‑appeared in a range of other publications, the Editor of International Journal of Oncology has decided that this paper should be retracted from the Journal. The authors were asked for an explanation to account for these concerns, but the Editorial Office did not receive a reply. The Editor apologizes to the readership for any inconvenience caused. [International Journal of Oncology 50: 85‑92, 2017; DOI: 10.3892/ijo.2016.3797]

Following the publication of the above paper, it has been drawn to the Editor's attention by a concerned reader that, regarding the experiments showing the expression of CD133 (Fig. 2A) and nucleostemin (NC) (Fig. 2C) on p. 684, the ACTB data for the CT26 and CMT93 cell lines in both figure parts appeared to be matching, suggesting that this figure may have been assembled incorrectly. The authors have been contacted by the Editorial Office to offer an explanation for this apparent anomaly in the presentation of the data in this paper, and we are awaiting their response. Owing to the fact that the Editorial Office has been made aware of this potential issue surrounding the scientific integrity of this paper, we are issuing an Expression of Concern to notify readers of this potential problem while the Editorial Office continues to investigate this matter further. [Oncology Letters 14: 681‑686, 2017; DOI: 10.3892/ol.2017.6190]

Ovarian clear cell carcinoma is characterized by HNF-1ß overexpression and is known to be resistant to chemotherapy. An inhibitor screening that specifically targets HNF-1ß led us to identify Actinonin as a candidate for cancer treatment. Actinonin, which is known to inhibit aminopeptidase M, has also been recognized for its antibacterial properties. We confirmed that GSK-3ß interference/inhibition, as a component of the HNF-1ß pathway, combined with Actinonin, has a highly potent antitumor effect compared to monotherapy. The same effect was observed in renal clear cell carcinoma lines expressing HNF-1ß. Actinonin promoted mitochondrial production by suppressing aerobic respiration, which decreased AMPK levels and increased ROS production. However, it also elevated GADD45α expression and induced mitophagy. GSK-3ß inhibition suppressed glycolysis and shifted energy production to OXPHOS, leading to increased ROS production. Furthermore, this combination produced excess ROS beyond metabolic capacity, which accumulated in lipid bilayers, leading to a further increase in CHOP gene expression and suppression of mitochondrial turnover. The GSK-3ß inhibitor and Actinonin combination demonstrated a powerful tumor-suppressive effect in vivo without severe side effects. Combining GSK-3ß inhibition with Actinonin can effectively eliminate cancer cells with HNF-1ß overexpression by inhibiting glycolysis and promoting mitochondrial turnover, highlighting new options for cancer therapy.

Osteosarcoma is the most common primary malignant bone tumor in adolescents and young adults; yet survival outcomes have remained stagnated for decades, underscoring the urgent need for new therapeutic strategies. Creatine kinase (CK)—comprising cytosolic CKB and mitochondrial CK—maintains malignant behaviors by supporting high-energy phosphate transfer through the phosphocreatine (pCr) shuttle. Here, we pharmacologically inhibited CK activity in osteosarcoma models and evaluated proliferation, cell death modalities, mitochondrial function, stemness, motility, and tumor behavior. CK blockade consistently suppressed growth and clonogenicity and induced apoptosis as the predominant mode of death. It impaired ATP buffering capacity and disturbed mitochondrial homeostasis, accompanied by reduced expression of stemness-associated markers and diminished migration and invasion. In mouse models, CK inhibition significantly restrained tumor progression and dissemination. These results indicate that disabling the CK-pCr energy-buffering system reprograms cellular energetics toward apoptosis and less aggressive phenotypes. Our findings support targeting the CK pathway as a tractable metabolic vulnerability and a rational partner for cytotoxic regimens, with pathway-specific signaling alterations representing downstream consequences of central energetic collapse.

Long-chain fatty acids (LCFAs) have emerged as important regulators of cancer metabolism, but their impact on hormone receptor expression in breast cancer (BCA) remains poorly understood. In this study, we investigated the effects of five LCFAs—linoleic acid (LA), oleic acid (OA), elaidic acid (EA), palmitic acid (PA), and α-linolenic acid (LNA)—on two BCA cell lines: luminal-type MCF7 and triple-negative MDA-MB-231 (MB231). All LCFAs suppressed cell viability and mitochondrial function in a dose-dependent manner, accompanied by decreased membrane potential, increased reactive oxygen species production, and a metabolic shift. Notably, OA reduced both mRNA and nuclear protein levels of estrogen receptor alpha (ERα) in MCF7 cells, leading to impaired responses to estradiol and tamoxifen. In contrast, PA induced nuclear ERα expression in MB231 cells, although ER signaling remained inactive. MicroRNA profiling revealed that OA upregulated ER-suppressive miR-22 and miR-221 in MCF7, while PA increased miR-34a in MB231, contributing to ERα induction. These findings suggest that specific LCFAs modulate ER expression through epigenetic and post-transcriptional mechanisms, altering hormonal responsiveness in BCA. Our results offer new insights into how dietary lipids may influence therapeutic efficacy and tumor behavior by regulating nuclear receptor signaling.

Myocardial injury is a critical determinant of prognosis in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection; however, its underlying mechanisms remain incompletely understood. In this study, we examined the effects of SARS-CoV-2-derived RNA fragments on human cardiomyocytes. We identified a 19-nucleotide sequence within the viral genome that shares complete sequence homology with the human F1F0 ATP synthase subunit alpha gene (ATP5A). This sequence was found to associate with Argonaute 2 (AGO2) and downregulate ATP5A expression via a mechanism analogous to RNA interference. Consequently, oxidative phosphorylation was suppressed in cardiomyocytes, leading to impaired myocardial maturation and the emergence of heart failure-like phenotypes. Notably, exosome-mimetic liposomal delivery of this RNA fragment to cardiomyocytes reproduced the ATP5A-suppressive effect. These findings suggest that SARS-CoV-2-derived RNA fragments may contribute to myocardial injury through the siRNA-like modulation of mitochondrial gene expression. Further validation in animal models and patient-derived materials is warranted.

Cancer-associated sarcopenia is closely linked to the prognosis of cancer patients, making its management a critical aspect of cancer treatment. Branched-chain amino acids (BCAAs) are known to promote skeletal muscle growth in healthy individuals; however, their efficacy in cancer patients remains controversial. In this study, we investigated the effects of BCAAs on cancer-associated sarcopenia to identify the underlying mechanisms that may suppress their effectiveness. In both a mouse cachexia model and an in vitro cachexia model, BCAAs did not significantly reduce oxidative stress, improve oxidative phosphorylation, suppress cytokine production, or enhance muscle mass and maturation, as observed in non-cancer-bearing models. Furthermore, treatment with 5-fluorouracil exacerbated sarcopenia in the mouse cachexia model, independent of tumor weight reduction, and this deterioration was not ameliorated by a BCAA-supplemented diet. The ineffectiveness of BCAAs was attributed to impaired BCAA catabolism, characterized by the decreased expression of branched-chain α-ketoacid dehydrogenase (BCKD) and increased levels of its inactive phosphorylated form, which were driven by elevated expression of BCKD kinase. These metabolic alterations were induced by high-mobility group box-1 (HMGB1). Notably, caprylic acid reversed these impairments in BCAA metabolism, thereby restoring BCAA efficacy. Our findings suggest that enhancing BCAA metabolism may improve their therapeutic potential in the treatment of cancer-associated sarcopenia.

Background/Objectives: Prostate cancer (PCa) cells may acquire radioresistance during radiation therapy (RT), resulting in PCa recurrence. This study was aimed at investigating the radiosensitizing effect of 5-aminolevulinic acid (5-ALA) on radioresistant PCa cells. Methods: Radioresistant PCa cells were developed through successive irradiation of two human PCa cell lines (PC-3 and DU 145) and a murine PCa cell line (Myc-CaP). The radiosensitivity of these PCa cells and the radiosensitizing effect of 5-ALA were evaluated using clonogenic assays. Mitochondrial accumulation of protoporphyrin IX (PpIX) and mitochondrial reactive oxygen species (ROS) were evaluated. A syngeneic mouse model with radioresistant PCa was established, and the immunohistochemistry of cell specimens from PCa patients with local recurrence after primary RT was examined. Results: Radioresistant PCa cells showed lower radiosensitivity compared to parental PCa cells. In radioresistant PCa cells with 5-ALA administration, compared to the group administered irradiation alone, the survival rate after irradiation was significantly reduced by promoting mitochondria-mediated apoptosis caused by increased PpIX accumulation and mitochondrial ROS generation. Similar results were observed in vivo. However, compared with parental PCa cells, radioresistant PCa cells were less affected by the radiosensitizing effect of 5-ALA, owing to decreased PpIX accumulation and mitochondrial ROS production caused by upregulated expression of the drug transporter ABCG2. ABCG2 expression was upregulated in human PCa specimens with post-RT recurrence. Conclusions: 5-ALA enhanced the antitumor effects of RT in radioresistant PCa cells; however, ABCG2 upregulation decreased PpIX accumulation, resulting in a reduced radiosensitizing effect of 5-ALA on radioresistant PCa cells compared with that on parental PCa cells. ABCG2 could be a potential therapeutic target for overcoming radioresistance.

Lauric acid (LAA) is a 12-carbon medium-chain fatty acid that reportedly has antitumor and muscle-protecting effects. However, the details of these antitumor effects remain unclear. Therefore, in this study, we investigated the mechanism underlying the antitumor effects of LAA in CT26 and HT29 colorectal cancer (CRC) cell lines. Our in vitro findings demonstrated that LAA suppressed CRC cell proliferation, induced mitochondrial oxidative stress (reactive oxygen species (ROS)), inhibited oxidative phosphorylation (OXPHOS), and induced apoptosis. Moreover, in vivo analysis of LAA showed a more pronounced antitumor effect in CT26 cells in a syngeneic mouse tumor model than in vitro; therefore, we further investigated its impact on host antitumor immunity. We observed that LAA increased the number of effector T cells in mouse tumors, while in vitro LAA activated mouse splenocytes (SplC) and promoted OXPHOS. In two-dimensional co-culture of SplC and CT26 cells, LAA induced cell death in cancer cells. In three-dimensional co-culture, LAA promoted SplC infiltration and suppressed the formation of tumor spheres. Thus, LAA may exert antitumor effects through increased ROS production in cancer cells and effector T cell activation via increased energy metabolism. These results suggest that LAA, when used in combination with existing anti-cancer drugs, is likely to exhibit sensitizing effects in terms of both antitumor and antitumor immune effects, and future clinical studies are anticipated.