Advances in Targeted Drug Resistance Associated with Dysregulation of Lipid Metabolism in Hepatocellular Carcinoma.

Hepatocellular carcinoma is the prevailing malignant neoplasm affecting the liver, often diagnosed at an advanced stage and associated with an unfavorable overall prognosis. Sorafenib and Lenvatinib have emerged as first-line therapeutic drugs for advanced hepatocellular carcinoma, improving the prognosis for these patients. Nevertheless, the issue of tyrosine kinase inhibitor (TKI) resistance poses a substantial obstacle in the management of advanced hepatocellular carcinoma. The pathogenesis and advancement of hepatocellular carcinoma exhibit a close association with metabolic reprogramming, yet the attention given to lipid metabolism dysregulation in hepatocellular carcinoma development remains relatively restricted. This review summarizes the potential significance and research progress of lipid metabolism dysfunction in Sorafenib and Lenvatinib resistance in hepatocellular carcinoma. Targeting hepatocellular carcinoma lipid metabolism holds promising potential as an effective strategy to overcome hepatocellular carcinoma drug resistance in the future.

Overexpressed FAM111B degrades GSDMA to promote esophageal cancer tumorigenesis and cisplatin resistance.

BACKGROUND: Chemotherapeutic agents such as cisplatin are commonly used in patients with clinically unresectable or recurrent esophageal cancer (ESCA). However, patients often develop resistance to cisplatin, which in turn leads to a poor prognosis. Studies have shown that FAM111B may be involved in the development of tumors as an oncogene or tumor suppressor gene. However, the pathological role and corresponding mechanism of FAM111B in ESCA are still unclear. METHODS: The GEPIA web tool, ENCORI Pan-Cancer Analysis Platform and UALCAN-TCGA database were used to study the expression of FAM111B in ESCA. CCK-8, angiogenesis, Transwell and xenograft assays were applied to explore the biological function of FAM111B in ESCA. Western blot, RT-qPCR, and RNA-seq analyses were applied to study the FAM111B/GSDMA axis in the progression of ESCA cells. CCK-8 and xenograft assays were used to study the role of the FAM111B/GSDMA axis in determining the sensitivity of ESCA to cisplatin. RESULTS: Our results demonstrated that FAM111B is highly expressed in ESCA tissues compared to normal tissues. We showed that FAM111B promotes the progression of ESCC cells by binding to GSDMA and that the trypsin protease domain is essential for the activity of FAM111B. Furthermore, we showed that the FAM111B/GSDMA axis regulates cisplatin sensitivity in ESCA. CONCLUSIONS: Overall, we identified a novel FAM111B/GSDMA axis regulating ESCA tumorigenesis and chemosensitivity, at least in ESCC cells.

SHC4 orchestrates ß-catenin pathway-mediated metastasis in triple-negative breast cancer by promoting Src kinase autophosphorylation.

Triple-negative breast cancer (TNBC) is highly aggressive and metastatic, and has the poorest prognosis among all breast cancer subtypes. Activated ß-catenin is enriched in TNBC and involved in Wnt signaling-independent metastasis. However, the underlying mechanisms of ß-catenin activation in TNBC remain unknown. Here, we found that SHC4 was upregulated in TNBC and high SHC4 expression was significantly correlated with poor outcomes. Overexpression of SHC4 promoted TNBC aggressiveness in vitro and facilitated TNBC metastasis in vivo. Mechanistically, SHC4 interacted with Src and maintained its autophosphorylated activation, which activated ß-catenin independent of Wnt signaling, and finally upregulated the transcription and expression of its downstream genes CD44 and MMP7. Furthermore, we determined that the PxPPxPxxxPxxP sequence on CH2 domain of SHC4 was critical for SHC4-Src binding and Src kinase activation. Overall, our results revealed the mechanism of ß-catenin activation independent of Wnt signaling in TNBC, which was driven by SHC4-induced Src autophosphorylation, suggesting that SHC4 might be a potential prognostic marker and therapeutic target in TNBC.

Lysosomal cyst(e)ine storage potentiates tolerance to oxidative stress in cancer cells.

Cyst(e)ine is a key precursor for the synthesis of glutathione (GSH), which protects cancer cells from oxidative stress. Cyst(e)ine is stored in lysosomes, but its role in redox regulation is unclear. Here, we show that breast cancer cells upregulate major facilitator superfamily domain containing 12 (MFSD12) to increase lysosomal cyst(e)ine storage, which is released by cystinosin (CTNS) to maintain GSH levels and buffer oxidative stress. We find that mTORC1 regulates MFSD12 by directly phosphorylating residue T254, while mTORC1 inhibition enhances lysosome acidification that activates CTNS. This switch modulates lysosomal cyst(e)ine levels in response to oxidative stress, fine-tuning redox homeostasis to enhance cell fitness. MFSD12-T254A mutant inhibits MFSD12 function and suppresses tumor progression. Moreover, MFSD12 overexpression correlates with poor neoadjuvant chemotherapy response and prognosis in breast cancer patients. Our findings reveal the critical role of lysosomal cyst(e)ine storage in adaptive redox homeostasis and suggest that MFSD12 is a potential therapeutic target.

Inhibition of DPAGT1 suppresses HER2 shedding and trastuzumab resistance in human breast cancer.

Human epidermal growth factor receptor 2-targeted (HER2-targeted) therapy is the mainstay of treatment for HER2+ breast cancer. However, the proteolytic cleavage of HER2, or HER2 shedding, induces the release of the target epitope at the ectodomain (ECD) and the generation of a constitutively active intracellular fragment (p95HER2), impeding the effectiveness of anti-HER2 therapy. Therefore, identifying key regulators in HER2 shedding might provide promising targetable vulnerabilities against resistance. In the current study, we found that upregulation of dolichyl-phosphate N-acetylglucosaminyltransferase (DPAGT1) sustained high-level HER2 shedding to confer trastuzumab resistance, which was associated with poor clinical outcomes. Upon trastuzumab treatment, the membrane-bound DPAGT1 protein was endocytosed via the caveolae pathway and retrogradely transported to the ER, where DPAGT1 induced N-glycosylation of the sheddase - ADAM metallopeptidase domain 10 (ADAM10) - to ensure its expression, maturation, and activation. N-glycosylation of ADAM10 at N267 protected itself from ER-associated protein degradation and was essential for DPAGT1-mediated HER2 shedding and trastuzumab resistance. Importantly, inhibition of DPAGT1 with tunicamycin acted synergistically with trastuzumab treatment to block HER2 signaling and reverse resistance. These findings reveal a prominent mechanism for HER2 shedding and suggest that targeting DPAGT1 might be a promising strategy against trastuzumab-resistant breast cancer.

The YTHDC1/GLUT3/RNF183 axis forms a positive feedback loop that modulates glucose metabolism and bladder cancer progression.

Aberrant glucose metabolism is a characteristic of bladder cancer. Hyperglycemia contributes to the development and progression of bladder cancer. However, the underlying mechanism by which hyperglycemia promotes the aggressiveness of cancers, especially bladder cancer, is still incompletely understood. N6-methyladenosine (m6A) modification is a kind of methylation modification occurring at the N6 position of adenosine that is important for the pathogenesis of urological tumors. Recently, it was found that the m6A reader YTHDC1 is regulated by high-glucose conditions. In our study, we revealed that YTHDC1 is not only regulated by high-glucose conditions but is also downregulated in bladder cancer tissue and associated with the prognosis of cancer. We also showed that YTHDC1 suppresses the malignant progression of and the glycolytic process in bladder cancer cells in an m6A-dependent manner and determined that this effect is partially mediated by GLUT3. Moreover, GLUT3 was found to destabilize YTHDC1 by upregulating RNF183 expression. In summary, we identified a novel YTHDC1/GLUT3/RNF183 feedback loop that regulates disease progression and glucose metabolism in bladder cancer. Collectively, this study provides new insight regarding the pathogenesis of bladder cancer under hyperglycemic conditions and might reveal ideal candidates for the development of drugs for bladder cancer.

ZDHHC2-Mediated AGK Palmitoylation Activates AKT-mTOR Signaling to Reduce Sunitinib Sensitivity in Renal Cell Carcinoma.

Tyrosine kinase inhibitors (TKI) that can suppress the VEGF signaling pathway and angiogenesis have been developed to impede the progression of malignant tumors and have been approved as first-line targeted agents for clear cell renal cell carcinoma (ccRCC). Dysregulation of lipid metabolism is a major driver of TKI resistance in renal cancer. In this study, we showed that the palmitoyl acyltransferase ZDHHC2 is abnormally upregulated in tissues and cell lines resistant to TKIs, such as sunitinib. Upregulation of ZDHHC2 contributed to sunitinib resistance in cells and mice, and ZDHHC2 regulated angiogenesis and cell proliferation in ccRCC. Mechanistically, ZDHHC2 mediated AGK S-palmitoylation to promote translocation of AGK into the plasma membrane and activation of the PI3K-AKT-mTOR signaling pathway in ccRCC, which modulated sunitinib sensitivity. In conclusion, these results identify a ZDHHC2-AGK signaling axis and suggest that ZDHHC2 is a targetable candidate for improving the antitumor efficacy of sunitinib in ccRCC. SIGNIFICANCE: ZDHHC2 confers sunitinib resistance to clear cell renal cell carcinoma by catalyzing AGK palmitoylation to activate the AKT-mTOR pathway.

Global crotonylome reveals hypoxia-mediated lamin A crotonylation regulated by HDAC6 in liver cancer.

Lysine crotonylation is a recently discovered post-translation modification involved in transcription regulation, cell signal transduction, and other processes. Scientists have identified several crotonylases and decrotonylases of histones, including P300/CBP, HDACs, and SIRTs. However, the regulation of non-histone protein crotonylation remains unclear. In the current study, we verified that crotonylation was upregulated in hypoxia and promoted liver cancer cell growth. We performed TMT-labeled quantitative lysine crotonylome analysis in 12 pairs of hepatocellular carcinoma and adjacent liver tissue and identified 3,793 lysine crotonylation sites in 1,428 proteins. We showed that crotonylation of lamin A at the site of K265/270 maintains its subcellular position, promotes liver cancer cell proliferation, and prevents cellular senescence. Our data indicate that HDAC6 is the decrotonylase of lamin A and downregulated in response to hypoxia, resulting in lamin A K265/270cr. Taken together, our study reveals the lamin A crotonylation in liver cancer progression and fills the research gap in non-histone protein crotonylation function.

E3 ubiquitin ligase RNF180 reduces sensitivity of triple-negative breast cancer cells to Gefitinib by downregulating RAD51.

BACKGROUND: Gefitinib (Gef) is an EGFR inhibitor and its resistance in triple negative breast cancer (TNBC) is a critical concern. E3 ubiquitin ligases are pivotal for mediation of TNBC metastasis. However, the role of E3 ubiquitin ligase Ring Finger Protein 180 (RNF180) in EGFR inhibitor resistance of TNBC remains unclear. This study was performed to investigate how the E3 ubiquitin protein ligase RNF180 manipulated the growth, metastasis, and resistance to Gef of TNBC cells. METHODS: TNBC tissues were harvested for detection of RNF180 and RAD51 expression. Gef-resistant cell lines were constructed. Next, gain- and loss-of-function assays were implemented in TNBC cell lines and Gef-resistant cell lines, followed by assessment of TNBC cell biological processes. IP assay was performed to detect the interaction between RNF180 and RAD51. Drug resistance-related genes (MRP1, BCRP, and MDR1) were evaluated by Western blot and RT-qPCR. The tumorigenesis was performed in nude mice to observe the growth and metastasis of TNBC in vivo. RESULTS: RAD51 was highly expressed in TNBC tissues and cells, while RNF180 was poorly expressed. Mechanistically, RNF180 degraded RAD51 by ubiquitination. Overexpression of RNF180 or silencing of RAD51 suppressed proliferation, invasion, migration, and Gef resistance of TNBC cells and accelerated their apoptosis. Upregulation of RNF180 or downregulation of RAD51 diminished tumorigenesis and Gef resistance of TNBC in mice. CONCLUSION: RNF180 degraded RAD51 by ubiquitination, thereby inhibiting TNBC cell growth and metastasis and sensitizing TNBC cells to Gef.

Tripartite motif-containing 3 (TRIM3) enhances ER signaling and confers tamoxifen resistance in breast cancer.

Tamoxifen resistance remains a clinical problem in estrogen receptor (ER)-positive breast cancer. SUMOylation of ERα enhances ERα-induced transcription activity. Tripartite motif-containing (TRIM) proteins are a new class of SUMO E3 ligases, which regulate the SUMOylation of proteins. However, the precise molecular mechanism and function of TRIM3 in SUMOylation and the response to tamoxifen remain unclear. In the present study, we observed that TRIM3 was dramatically overexpressed in breast cancer, which correlated with tamoxifen resistance. Furthermore, TRIM3 overexpression significantly correlated with poor survival of patients with ER+ breast cancer treated with tamoxifen. TRIM3 overexpression conferred cell survival and tumorigenesis, whereas knocking down of TRIM3 reduced these capabilities. Moreover, TRIM3, as a ubiquitin carrier protein 9 (UBC9) binding protein, promoted SUMO modification of estrogen receptor 1 (ESR1) and activated the ER pathway. Silencing UBC9 abolished the function of TRIM3 in regulating tamoxifen resistance. These results suggest TRIM3 as a novel biomarker for breast cancer therapy, indicating that inhibiting TRIM3 combined with tamoxifen might provide a potential treatment for breast cancer.

Prognostic Factors of Survival of Advanced Liver Cancer Patients Treated With Palliative Radiotherapy: A Retrospective Study.

AIMS: Survival benefit of liver cancer patients who undergo palliative radiotherapy varies from person to person. The present study aims to identify indicators of survival of advanced liver cancer patients receiving palliative radiotherapy. PATIENTS AND METHODS: One hundred and fifty-nine patients treated with palliative radiotherapy for advanced liver cancer were retrospectively assessed. Of the 159 patients, 103 patients were included for prediction model construction in training phase, while other 56 patients were analyzed for external validation in validation phase. In model training phase, clinical characteristics of included patients were evaluated by Kaplan-Meier curves and log-rank test. Thereafter, multivariable Cox analysis was taken to further identify characteristics with potential for prediction. In validation phase, a separate dataset including 56 patients was used for external validation. Harrell's C-index and calibration curve were used for model evaluation. Nomograms were plotted based on the model of multivariable Cox analysis. RESULTS: Thirty-one characteristics of patients were investigated in model training phase. Based on the results of Kaplan-Meier plots and log-rank tests, 6 factors were considered statistically significant. On multivariable Cox regression analysis, bone metastasis (HR = 1.781, P = 0.026), portal vein tumor thrombus (HR = 2.078, P = 0.015), alpha-fetoprotein (HR = 2.098, P = 0.007), and radiation dose (HR = 0.535, P = 0.023) show significant potential to predict the survival of advanced liver cancer patients treated with palliative radiotherapy. Moreover, nomograms predicting median overall survival, 1- and 2-year survival probability were plotted. The Harrell's C-index of the predictive model is 0.709(95%CI, 0.649-0.769) and 0.735 (95%CI, 0.666-0.804) for training model and validation model respectively. Calibration curves of the 1- and 2-year overall survival of the predictive model indicate that the predicted probabilities of OS are very close to the actual observed outcomes both in training and validation phase. CONCLUSION: Bone metastasis, portal vein tumor thrombus, alpha-fetoprotein and radiation dose are independent prognostic factors for the survival of advanced liver cancer patients treated with palliative radiotherapy.

Microstructure-Induced Anisotropic Optical Properties of YF3 Columnar Thin Films Prepared by Glancing Angle Deposition.

Yttrium fluoride (YF3) columnar thin films (CTFs) were fabricated by electron beam evaporation with the glancing angle deposition method. The microstructures and optical properties of YF3 CTFs were studied systematically. The YF3 films grown at different deposition angles are all amorphous. As the deposition angle increases, the columns in YF3 CTFs become increasingly separated and inclined, and the volume fraction of YF3 decreases, resulting in lower refractive indices. This phenomenon is attributed to the self-shadowing effect and limited adatom diffusion. The YF3 CTFs are optically biaxial anisotropic with the long axis (c-axis) parallel to the columns, the short axis (b-axis) perpendicular to the columns, and the other axis (a-axis) parallel to the film interface. The principal refractive index along the b-axis for the 82°-deposited sample is approximately 1.233 at 550 nm. For the 78°-deposited sample, the differences of principal refractive indices between the c-axis and the b-axis and between the a-axis and the b-axis reach the maximum 0.056 and 0.029, respectively. The differences of principal refractive indices were affected by both the deposition angle and the volume fraction of YF3.

Zinc finger protein 367 promotes metastasis by inhibiting the Hippo pathway in breast cancer.

Circulating tumor cells (CTC) disseminating is an important cause of distant metastasis. However, the mechanism involved in increasing the numbers of CTCs in breast cancer is unclear. Herein, Zinc finger protein 367 (ZNF367) was identified as a potential prometastatic gene in an integrative breast cancer datasets. ZNF367 was upregulated in breast cancer tissues and cell lines, and significantly correlated with poorer metastasis-free and overall survivals in patients. ZNF367 promoted tumor metastasis accompanied with increase of CTC numbers. Mechanistically, ZNF367 interacted with chromatin remodeling protein BRG1 and transcriptionally activated CIT and TP53BP2, leading to the inhibition of the Hippo pathway and activation of YAP1, which gave rise to the resistance of anoikis and increased CTCs in the blood circulation. More importantly, administration of a YAP1 inhibitor Verteporfin resensitized ZNF367-overexpressing breast cancer cells to anoikis and abrogated metastasis. Our findings addressed the importance of ZNF367 in breast cancer as a prognostic biomarker and offered a potential therapeutic strategy for the treatment of a subset of metastatic breast cancer with ZNF367 overexpression.

Oridonin inhibits aberrant AKT activation in breast cancer.

Aberrant activation of phosphatidylinosito-4,5-bisphosphate 3-kinase/protein kinase B (PI3K/AKT) signaling in cancer has led to pursuit of inhibitors for targeting this pathway. However, inhibitors of PI3K and AKT have failed to yield efficacious results without adverse effects. Here, we screened a library containing 441 authenticated traditional chinese medicine (TCM) plant extracts by examining their effect on cell viability of a human mammary epithelial cell line HMEC-PIK3CAH1047R, which expresses mutant PIK3CAH1047R and has constitutively active AKT signaling. We found that Oridonin, an extract from Rabdosia rubescens, reduced cell viability to the greatest extent. Oridonin binds to AKT1 and potentially functions as an ATP-competitive AKT inhibitor. Importantly, Oridonin selectively impaired tumor growth of human breast cancer cells with hyperactivation of PI3K/AKT signaling. Moreover, Oridonin prevented the initiation of mouse mammary tumors driven by PIK3CAH1047R. Our results suggest that Oridonin may serve as a potent and durable therapeutic agent for the treatment of breast cancers with hyperactivation of PI3K/AKT signaling.

Age-specific sex difference in the incidence of hepatocellular carcinoma in the United States.

BACKGROUND: Hepatocellular carcinoma possesses a notable sex difference in incidence, and a protective role of estrogens has been hypothesized. METHODS: Using data from 13 cancer registries in the Surveillance, Epidemiology, and End Results Program, we describe the age-specific sex difference in the incidence of hepatocellular carcinoma in the United States during 1992-2013. We used a curve fitting by non-linear regression to quantitatively characterize the age-specific incidence rate of hepatocellular carcinoma by sex. RESULTS: A total of 44,287 incident cases of hepatocellular carcinoma (33,196 males and 11,091 females) were included, with an overall male-to-female ratio in age-standardized rate of 3.55. The sex ratio was below 2 at ages <25 years, increased with age from ages 25-29 years until peaking at 5.40 at ages 50-54 years, and declined thereafter. We also observed additional peaks in the age-specific sex ratio curves at ages 25-34 years across racial/ethnic groups. Modelling of age-specific incidence rates indicated a 15-year delayed increase with age in females compared with males in Asian and Pacific Islanders, and an 11-year delay in Hispanic whites. CONCLUSIONS: The age-dependent patterns in the sex difference in the incidence of hepatocellular carcinoma support the hypothesis of a protective role of estrogens. The underlying reasons for the sex difference in hepatocellular carcinoma remain to be further explored in analytic epidemiological studies.

HN1 contributes to migration, invasion, and tumorigenesis of breast cancer by enhancing MYC activity.

BACKGROUND: Hematological and neurological expressed 1 (HN1) is upregulated in many tumors, but the role of HN1 in breast cancer progression and its regulatory mechanism have not been well understood. METHODS: To study the role of HN1 in the initiation and progression of breast cancer, we examined HN1 levels in breast cancer cells and tissues and analyzed the relationship between HN1 levels and patient survival. We used mammosphere formation assay, side population analysis, wound healing assay, transwell assay, soft agar formation assay, and xenografted tumor model to determine the effect of HN1 on the expansion of breast cancer stem cells, and the migration, invasion and tumorigenesis of breast cancer. To determine whether HN1 regulates MYC, we used quantitative real-time PCR and Western blot analysis to assess the expression of MYC and their targeted genes to determine the phenotype caused by knockdown of MYC in breast cancer cell with HN1 overexpression. RESULTS: In this study, we found that HN1 was upregulated in breast cancer tissues. Patients with high levels of HN1 expression had significantly shorter survival than those with low HN1 expression. In breast cancer cell line, ectopic overexpression of HN1 not only promoted the expansion of breast cancer stem cells, but also promoted cell migration, invasion, and tumorigenesis, while knockdown of HN1 reduced these effects. Furthermore, there was a positive correlation between MYC (also known as c-MYC) level and HN1 level, mechanism analysis suggested HN1 promoted the expression of MYC and its targeted genes like CDK4, CCND1, p21, CAV1, and SFRP1. Downregulation of MYC abrogated the effect of HN1 overexpression in breast cancer cell lines. CONCLUSION: Taken together, these data reveal that HN1 promotes the progression of breast cancer by upregulating MYC expression, and might be a therapeutic target for breast cancer.

Digitalis Use and the Risk of Breast Cancer: A Systematic Review and Meta-Analysis.

INTRODUCTION: Previous epidemiological studies have indicated an increased risk of breast cancer associated with digitalis medication, though results are inconsistent. We performed this systematic review of available epidemiological studies to clarify the association between digitalis use and the risk of breast cancer. METHODS: A search of studies published through May 2016 in MEDLINE and EMBASE databases was performed, supplemented by manual searches of reference lists. The quality of the included studies was assessed, and relative risks were pooled using both random- and fixed-effect models. RESULTS: Three case-control studies and six cohort studies were identified. Meta-analysis generated a pooled relative risk of 1.35 (95% confidence interval 1.24-1.46) in both fixed- and random-effect models. The heterogeneity test suggested low heterogeneity across studies. The funnel plot suggested no existence of publication bias. Subgroup analysis by study design revealed an increased risk of breast cancer associated with digitalis use from cohort studies only (relative risk = 1.39, 95% confidence interval 1.27-1.52), rather than from case-control studies. Studies with adjustment for tobacco smoking or body mass index generated lower overall estimates than those not adjusted. CONCLUSIONS: Existing epidemiological evidence regarding the association between digitalis use and the risk of breast cancer remains inconclusive and more well-designed studies are still needed.

Addition of the p110α inhibitor BYL719 overcomes targeted therapy resistance in cells from Her2-positive-PTEN-loss breast cancer.

Breast cancer is one of the leading causes of death for women worldwide. Among various subtypes of breast cancer, human epidermal growth factor receptor 2 (HER2)-positive and phosphatase and tensin homolog (PTEN) loss breast cancer is a cause of great concern in terms of its resistance to HER2-targeted therapies and its poor prognosis. Phosphatidylinositol 3-kinase (PI3K)/AKT hyperphosphorylation is considered one of key mechanisms leading to this resistance, thus combination therapy of PI3K inhibitors and HER2 antibodies is promising for overcoming this problem, and more specific regimens should be designed in this age of precision medicine. In this study, we established an HER2-positive and PTEN loss cell line and confirmed it by western blot analysis. This cell line and its orthotopic xenograft models were exposed to p110α-specific inhibitor BYL719, p110ß-specific inhibitor AZD6482, or pan-PI3K inhibitor BKM120, respectively, and the results showed sensitivity to both BYL719 and BKM120 but not AZD6482, which indicated a p110α-reliance for HER2-positive-PTEN-loss breast cancer. Then, the addition of BYL719 to HER2 antibody greatly reduced tumor growth both in vitro and in vivo, accompanied by inhibited PI3K effector phosphorylation. Therefore, our findings suggest that the combination of p110α-selective inhibitor BYL719 with HER2 antibody could be a potential strategy for more personalized treatment of HER2-posistive-PTEN-loss breast cancer; and in addition, the optimal schedule of this combination therapy needs to be further explored.

Gold nanorods as the saturable absorber for a diode-pumped nanosecond Q-switched 2 µm solid-state laser.

Gold nanorods (GNRs) with an average aspect ratio of 15 were experimentally exploited as the 2 µm saturable absorber in a laser diode pumped Tm:YAG laser for the first time, to the best of our knowledge. Q-switched pulses with a maximum average output power of 380 mW, a minimum pulse width of 796 ns, and a pulse repetition rate of 77 kHz were achieved under the LD pump power of 6.2 W. Our results indicate that GNRs with a large aspect ratio are promising saturable absorbers in the 2 µm wavelength region.