Thymosin α1 promotes the activation of myeloid-derived suppressor cells in a Lewis lung cancer model by upregulating Arginase 1

Mechanism and clinical application of thymosin in the treatment of lung cancer

Cancer is one of the leading causes of death worldwide. The burden of cancer on public health is becoming more widely acknowledged. Lung cancer has one of the highest incidence and mortality rates of all cancers. The prevalence of early screening, the emergence of targeted therapy, and the development of immunotherapy have all significantly improved the overall prognosis of lung cancer patients. The current state of affairs, however, is not encouraging, and there are issues like poor treatment outcomes for some patients and extremely poor prognoses for those with advanced lung cancer. Because of their potent immunomodulatory capabilities, thymosin drugs are frequently used in the treatment of tumors. The effectiveness of thymosin drugs in the treatment of lung cancer has been demonstrated in numerous studies, which amply demonstrates the potential and future of thymosin drugs for the treatment of lung cancer. The clinical research on thymosin peptide drugs in lung cancer and the basic research on the mechanism of thymosin drugs in anti-lung cancer are both systematically summarized and analyzed in this paper, along with future research directions.

Synergistic anti-cancer and attenuation effects of thymosin on chemotherapeutic drug vinorelbine in tumor-bearing zebrafish

Vinorelbine, the standard chemotherapy drug on advanced lung cancer, causes adverse events such as immunosuppression and bone marrow suppression. Thus, it is necessary to find drugs that could improve immune function and synergistically enhance the anti-tumor effect of vinorelbine. Thymosin is reported to inhibit tumor growth as an immunomodulator. Herein, to study the synergistic anti-cancer and attenuation effects of thymosin on vinorelbine, human lung cancer A549 cells that were labeled with CM-DiI were transplanted into zebrafish to establish the lung cancer xenotransplanted model. After treatment of vinorelbine and different concentrations of thymosin, the fluorescence intensity of CM-DiI-labeled A549 cells and the number of apoptotic muscle cells in the tumor-bearing zebrafish were detected. Besides, effects of thymosin on vinorelbine-reduced macrophages and T cells were identified in the transgenic zebrafish (Tg:zlyz-EGFP and Tg:rag2-DsRed). Then, the qRT-PCR was used to determine the alterations of the immune-related factors at the transcription level. Thymosin showed a marked synergistic anti-cancer effect with vinorelbine for the xenograft human lung cancer A549 cells, and the synergistic effect enhanced in a dose-dependent manner. Moreover, thymosin alleviated vinorelbine-induced muscle cell apoptosis, macrophage reduction, and T cell suppression. Compared with the vinorelbine group, co-administration with thymosin raised the mRNA levels of TNF-α, TNF-β, INF-γ, and GM-CSF. Thus, thymosin possesses synergistic anti-cancer effect on vinorelbine, and has protective effect on vinorelbine-induced immunosuppression. Thymosin, as an adjuvant immunomodulatory therapy, has great potential in enhancing the clinical application of vinorelbine.

Highlights into historical and current immune interventions for cancer

Immunotherapy is an additional pillar when combined with traditional standards of care such as chemotherapy, radiotherapy, and surgery for cancer patients. It has revolutionized cancer treatment and rejuvenated the field of tumor immunology. Several types of immunotherapies, including adoptive cellular therapy (ACT) and checkpoint inhibitors (CPIs), can induce durable clinical responses. However, their efficacies vary, and only subsets of cancer patients benefit from their use. In this review, we address three goals: to provide insight into the history of these approaches, broaden our understanding of immune interventions, and discuss current and future approaches. We highlight how cancer immunotherapy has evolved and discuss how personalization of immune intervention may address present limitations. Cancer immunotherapy is considered a recent medical achievement and in 2013 was selected as the "Breakthrough of the Year" by Science. While the breadth of immunotherapeutics has been rapidly expanding, to include the use of chimeric antigen receptor (CAR) T-cell therapy and immune checkpoint inhibitor (ICI) therapy, immunotherapy dates back over 3000 years. The expansive history of immunotherapy, and related observations, have resulted in several approved immune therapeutics beyond the recent emphasis on CAR-T and ICI therapies. In addition to other classical forms of immune intervention, including human papillomavirus (HPV), hepatitis B, and the Mycobacterium bovis Bacillus Calmette-Guérin (BCG) tuberculosis vaccines, immunotherapies have had a broad and durable impact on cancer therapy and prevention. One classic example of immunotherapy was identified in 1976 with the use of intravesical administration of BCG in patients with bladder cancer; resulting in a 70 % eradication rate and is now standard of care. However, a greater impact from the use of immunotherapy is documented by the prevention of HPV infections that are responsible for 98 % of cervical cancer cases. In 2020, the World Health Organization (WHO) estimated that 341,831 women died from cervical cancer [1]. However, administration of a single dose of a bivalent HPV vaccine was shown to be 97.5 % effective in preventing HPV infections. These vaccines not only prevent cervical squamous cell carcinoma and adenocarcinoma, but also oropharyngeal, anal, vulvar, vaginal, and penile squamous cell carcinomas. The breadth, response and durability of these vaccines can be contrasted with CAR-T-cell therapies, which have significant barriers to their widespread use including logistics, manufacturing limitations, toxicity concerns, financial burden and lasting remissions observed in only 30 to 40 % of responding patients. Another, recent immunotherapy focus are ICIs. ICIs are a class of antibodies that can increase the immune responses against cancer cells in patients. However, ICIs are only effective against tumors with a high mutational burden and are associated with a broad spectrum of toxicities requiring interruption of administration and/or administration corticosteroids; both of which limit immune therapy. In summary, immune therapeutics have a broad impact worldwide, utilizing numerous mechanisms of action and when considered in their totality are more effective against a broader range of tumors than initially considered. These new cancer interventions have tremendous potential notability when multiple mechanisms of immune intervention are combined as well as with standard of care modalities.

Thymosin alpha 1 as an adjuvant to hyperthermic intraperitoneal chemotherapy in an experimental model of peritoneal metastases from colonic carcinoma

INTRODUCTION

Heated intraperitoneal chemotherapy (HIPEC) is currently implemented in the treatment of peritoneal metastases from colorectal carcinoma (PM-CRC) origin. However, recurrence is common and the effectiveness of HIPEC has been questioned. The aim of this study was to evaluate the use of thymosin alpha 1 (Tα1), an immunomodulatory molecule, as an adjuvant to HIPEC treatment.

METHODS

We developed an experimental model of HIPEC by the induction of PM-CRC in C57BL mice and intra-abdominal perfusion of mitomycin C (MMC). Mice were treated with Tα1 at 0.6 mg/kg for 5 days after HIPEC. Clinical and immunological parameters were compared between HIPEC and HIPEC + Tα1 groups.

RESULTS

Treatment with Tα1 increased overall survival of mice compared to HIPEC treatment alone and sham-treated animals (16.1 ± 0.8 vs. 14.1 ± 0.6 and 11.8 ± 0.8, respectively, p = 0.02). Tα1 had no direct anti-tumor effect, as seen by lack of inhibition of tumor cell proliferation. Tα1 treatment induced a T helper (Th) 1 immune response in tumor metastases as evidenced by a significant increase of the Th1-specific markers IFN-γ and T-bet (1.21 ± 0.3 vs. 0.52 ± 0.08, p < 0.05; 0.88 ± 0.04 vs. 0.64 ± 0.14, p < 0.05, respectively). This Th1 skew was accompanied by increased CD8⁺ infiltration into omental and visceral metastases by Tα1 treatment compared to sham and HIPEC-treated animals (21.24 ± 2.16 vs. 10.45 ± 0.89 and 7.7 ± 1.3, p < 0.001; 14.12 ± 1.54 vs. 12.12 ± 0.01 and 6.64 ± 0.87, p < 0.01, respectively).

CONCLUSIONS

Tα1 augments the effect of HIPEC by the induction of a Th1 anti-tumor immune response. Further experiments should evaluate Tα1 and other novel immunomodulators in order to exploit the immunological opportunities created by HIPEC.

Interleukin-1beta triggers the expansion of circulating granulocytic myeloid-derived suppressor cell subset dependent on Erk1/2 activation

Chronic inflammation contributes to cancer development and progression. Although interleukin-1beta (IL-1β) has been observed to be associated with an general immune suppression of T cell response and the immunosuppression strongly correlates with accumulation of myeloid-derived suppressor cells (MDSCs), the relationship and mechanism between MDSCs expansion and IL-1β expression remain ambiguous. Here, we showed that the concentration of IL-1β was highly correlated with G-MDSC subset, rather than mo-MDSC subset. Recombinant IL-1β increased the percentage of G-MDSCs in the blood of tumor-bearing mice, and IL-1Ra attenuated the accumulation of G-MDSCs in the tumor-bearing mice. In addition, the IL-1β-overexpressing B16F10 cells induced higher level of G-MDSCs compared with wild-type B16F10 cells. Moreover, we found that the accumulation of G-MDSCs induced by IL-1β was dependent on the activation of extracellular signal-regulated kinases 1 and 2 (Erk1/2). Collectively, these findings show a novel role of IL-1β in G-MDSCs accumulation by activating Erk1/2, which suggests that IL-1β elimination or Erk1/2 signaling blockade could decrease G-MDSCs generation and thereby improve host immunosurveillance.

Thymic function affects breast cancer development and metastasis by regulating expression of thymus secretions PTMα and Tβ15b1

Breast cancer is currently one of the most common malignant tumors in women. Our previous research found that thymic dysfunction has a certain relationship with the occurrence and development of breast cancer. In order to explore whether the functional status of thymus is related to the development and metastasis of breast cancer, we use BALB/c wild type mice (BALB wt), BALB/c nude mice (BALB nu), BALB wt mice implanted with 4T1 cells (wt 4T1), BALB nu with 4T1 (nu 4T1), D-galactose treatment wt 4T1 mice (D-Gal), Thymalfasin treatment wt 4T1 mice (Tα1), Cyclophosphamide treatment wt 4T1 mice (CTX), Doxorubicin treatment wt 4T1 mice (Dox) in the research. As a result, nu 4T1, D-Gal and DOX had earlier lung metastases. Gene chip results showed that PTMα and Tβ15b1 were the most up-regulated and down-regulated genes in thymosin-related genes, respectively. Overexpression or silencing of PTMα and Tβ15b1 genes did not affect the proliferation of 4T1 cells. PTMα gene silenced, cell migration and invasion ability enhanced, while PTMα gene overexpression, the cell invasion ability weaken. In vivo, PTMα gene overexpression promotes tumor growth and lung metastasis in the early stage, but has no significant effect in the later stage. Tβ15b1 overexpression also promotes tumor growth in the early stage, but suppresses in the later stage. Tβ15b1 gene silencing inhibits tumor lung metastasis. Thus, our findings demonstrated that thymic function affects breast cancer development and metastasis by regulating expression of thymus secretions PTMα and Tβ15b1. Our study provided new directions for breast cancer therapy.

Thymosin alpha-1 blocks the accumulation of myeloid suppressor cells in NSCLC by inhibiting VEGF production

BACKGROUND

Thymosin alpha-1 (TA) has been reported to inhibit tumor growth as an immunomodulator. However, its mechanism of action in immunosuppressive cells is unclear. The purpose of this study was to investigate whether TA can reshape the immune microenvironment by inhibiting the function of myeloid-derived suppressor cells (MDSCs) in non-small cell lung carcinoma (NSCLC).

METHODS

The effects of TA on peripheral blood monocytic MDSCs (M-MDSCs) in patients with NSCLC and on the apoptosis and migration of M-MDSCs were studied. A mouse subcutaneous xenograft tumor model was constructed, and the effect of TA on M-MDSC migration was evaluated. Quantitative real-time PCR, Western blotting, flow cytometry and immunohistochemistry were used to examine the mechanism by which TA affects M-MDSCs.

RESULTS

TA not only promoted the apoptosis of M-MDSCs by reducing the Bcl-2/BAX ratio but also and more importantly inhibited the migration of MDSCs to the tumor microenvironment by suppressing the production of vascular endothelial growth factor (VEGF) through the downregulation of hypoxia-inducible factor (HIF)-1α in tumor cells.

CONCLUSIONS

TA may have a novel antitumor effect mediated by decreasing M-MDSC accumulation in the tumor microenvironment through reduced VEGF production.

A Reappraisal of Thymosin Alpha1 in Cancer Therapy

Thymosin alpha1 (Tα1), an endogenous peptide first isolated from the thymic tissue in the mid-sixties, has gained considerable attention for its immunostimulatory activity that led to its application to diverse pathological conditions, including cancer. Studies in animal models and human patients have shown promising results in different types of malignancies, especially when Tα1 was used in combination with other chemo- and immune therapies. For this reason, the advancements in our knowledge on the adjuvant role of Tα1 have moved in parallel with the development of novel cancer therapies in a way that Tα1 was integrated to changing paradigms and protocols, and tested for increased efficacy and safety. Cancer immunotherapy has recently experienced a tremendous boost following the development and clinical application of immune checkpoint inhibitors. By unleashing the full potential of the adaptive immune response, checkpoint inhibitors were expected to be very effective against tumors, but it soon became clear that a widespread and successful application was not straightforward and shortcomings in efficacy and safety clearly emerged. This scenario led to the development of novel concepts in immunotherapy and the design of combination protocols to overcome these limitations, thus opening up novel opportunities for Tα1 application. Herein, we summarize in a historical perspective the use of Tα1 in cancer, with particular reference to melanoma, hepatocellular carcinoma and lung cancer. We will discuss the current limitations of checkpoint inhibitors in clinical practice and the mechanisms at the basis of a potential application of Tα1 in combination protocols.

Thymosin alpha-1; a natural peptide inhibits cellular proliferation, cell migration, the level of reactive oxygen species and promotes the activity of antioxidant enzymes in human lung epithelial adenocarcinoma cell line (A549)

This research was conducted to investigate the biochemical effects of thymosin alpha-1 using human lung cancer cells (A549). The A549 cells were treated with different concentrations of Thα1 for 24 h and the growth, inhibition of cells was determined. Thα1 revealed anti-proliferative effect at 24 and 48 μg/ml after 24 h. Furthermore, it indicated antioxidant properties by significantly enhancing the activity of catalase (12 μg/ml), superoxide dismutase (6 and 12 μg/ml), and glutathione peroxidase (3, 6 and 12 μg/ml) and reducing the production of cellular ROS. Our results showed that Thα1 inhibits the migration of A549 cells in a concentration-dependent manner after 24 and 48 h. Moreover, the effect of Thα1 on apoptosis was investigated by Hoechst 33342 staining and cell cycle analysis. Results demonstrated no significant effect on the induction of apoptosis in A549 cells. In conclusion, our results showed the antioxidant properties of Thα1 on A549 cancer cells.

MicroRNA-21 promotes the proliferation, migration and invasion of non-small cell lung cancer A549 cells by regulating autophagy activity via AMPK/ULK1 signaling pathway

The present study investigated the expression of microRNA (miR)-21 in non-small cell lung cancer (NSCLC) tissues, its biological functions and mechanism of autophagy regulation. A total of 46 patients with NSCLC were enrolled in the present study. To measure the expression of miR-21, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was employed. NSCLC A549 cells were transfected with miR-negative control (NC), miR-21 mimics or inhibitor. The CCK-8 assay was used to investigate the proliferation of A549 cells. To study migration and invasion abilities of A549 cells, The Transwell assay was performed. In addition, to determine the expression levels of ULK1, LC3B, AMPKα, p-AMPKα and p62 proteins, western blotting was conducted and laser confocal microscopy was performed to observe the formation of autophagosomes in A549 cells. To explore whether miR-21 regulates the biological functions of A549 cells via autophagy, an autophagy inhibitor, 3-MA, or agonist, rapamycin, were used in a rescue assay. Results indicated that miR-21 expression in NSCLC tissues was enhanced, and closely correlated with the occurrence and development of NSCLC. In vitro experiments showed that miR-21 mimics promoted the proliferation, migration and invasion of A549 cells, while miR-21 inhibitor inhibited these biological functions. Western blotting indicated that miR-21 upregulated autophagy marker LC3BII protein, but downregulated p62 protein. Laser confocal microscopy showed that miR-21 activated autophagy of A549. Rescue experiments indicated that autophagy reversed the effect of miR-21 on the proliferation, migration and invasion of A549 cells. Western blotting data suggested that autophagy-related AMPK/ULK1 signaling pathway was activated by miR-21, and interference or overexpression of ULK1 reversed the biological functions of miR-21. The present study demonstrated that miR-21 expression in NSCLC tissues was upregulated and positively correlated with lymphatic metastasis and clinical staging. In addition, miR-21 regulated autophagy activity of NSCLC A549 cells via AMPK/ULK1 signaling pathway, and promoted the proliferation, migration and invasion of NSCLC A549 cells.

A novel mechanism of tumor-induced thymic atrophy in mice bearing H22 hepatocellular carcinoma

Background

Thymic atrophy was discovered in tumor-bearing mice in recent years.

Methods

Flow cytometry was carried out including Annexin V-FITC/PI double staining, PI staining, Terminal dUTP nick-end labeling, CD3-FITC/CD19-PE and CD8-FITC/CD4-PE double staining. Enzyme-linked immunosorbent assay and polymerase chain reaction were also investigated.

Results

According to our experiments, we demonstrated that no signs of apoptosis in thymocytes were found in H22-bearing mice, while the proportions of CD4⁺ T cells and CD8⁺ T cells in thymuses were remarkably increased, the opposite tendency was found in peripheral bloods, and only CD3⁺CD8⁺ T cells were discovered in H22 solid tumors. We further discovered that the level of thymosin alpha 1 (Tα1) and the expression of Wnt4 in thymus of H22-bearing mice were significantly improved than control, which indicated the active proliferation and differentiation of thymocytes. Our study revealed that CD8⁺ T cells could not effectively eliminate H22 cells independently when CD4⁺ T cells were suppressed by tumors, while the body would only enhance the differentiation and maturation of T cells in thymuses and release them to solid tumor to reinforce antitumor immunocompetence, leading to a vicious cycle which finally led to thymic atrophy.

Conclusion

Our data propose a novel mechanism of tumor-induced thymic atrophy regulated by abnormal immunoreaction and may provide new ideas for the immunotherapy of tumors.