Chemotherapy Resistance Molecular Mechanism in Small Cell Lung Cancer

Orchestrating smart therapeutics to achieve optimal treatment in small cell lung cancer: recent progress and future directions

Small cell lung cancer (SCLC) is a recalcitrant malignancy with elusive mechanism of pathogenesis and dismal prognosis. Over the past decades, platinum-based chemotherapy has been the backbone treatment for SCLC. However, subsequent chemoresistance after initial effectiveness urges researchers to explore novel therapeutic targets of SCLC. Recent years have witnessed significant improvements in targeted therapy in SCLC. New molecular candidates such as Ataxia telangiectasia and RAD3-related protein (ATR), WEE1, checkpoint kinase 1 (CHK1) and poly-ADP-ribose polymerase (PARP) have shown promising therapeutic utility in SCLC. While immune checkpoint inhibitor (ICI) has emerged as an indispensable treatment modality for SCLC, approaches to boost efficacy and reduce toxicity as well as selection of reliable biomarkers for ICI in SCLC have remained elusive and warrants our further investigation. Given the increasing importance of precision medicine in SCLC, optimal subtyping of SCLC using multi-omics have gradually applied into clinical practice, which may identify more drug targets and better tailor treatment strategies to each individual patient. The present review summarizes recent progress and future directions in SCLC. In addition to the emerging new therapeutics, we also focus on the establishment of predictive model for early detection of SCLC. More importantly, we also propose a multi-dimensional model in the prognosis of SCLC to ultimately attain the goal of accurate treatment of SCLC.

The impact of PD-L1 as a biomarker of cancer responses to combo anti-PD-1/CTLA-4

Combination therapy of solid tumors with immune checkpoint inhibitors (ICIs) is a promising and rapidly evolving area of clinical research. Combo nivolumab-ipilimumab therapy has demonstrated potent efficacy in recent years, and PD-L1 expression profile has shown to play a key role in determining the most optimal immunotherapeutic regimen in advanced cancer patients. Here, the focus is over the impact of PD-L1 on combo nivolumab-ipilimumab in advanced solid cancer patients. Interpretations of this review indicate that patient responses to combo nivolumab-ipilimumab can be affected from different levels of PD-L1 expression states. A point required attention is the variations in responses among diverse cancer types or between different doses of the immunotherapy drugs. In general, higher rates of responses are seen with higher PD-L1 expression levels in many cancer types. This, however, is not coincided with survival of patients. Taken all into consideration, it could be asserted that considering PD-L1 as a solo biomarker may not be reliable for predicting clinical efficacy of combo nivolumab-ipilimumab. Thus, a search for other biomarkers or combination of PD-L1 with other factors may be considered for predicting patient responses.

A bioinformatics-based study on the Cisplatin-resistant lung cancer cells; what are the orchestrators of this phenom?

Lung cancer represents a significant global health issue and is among the central causes of mortality and morbidity around the world. Unfortunately, the majority of lung cancer patients acquire drug resistant to chemotherapy either intrinsically or acquired after Cisplatin treatment. It is indicated that increasing or decreasing the expression of particular genes can affect chemotherapeutic sensitivity or resistance. As a result, gaining a deeper knowledge of the changed expression of genes implicated in lung cancer drug resistance, as well as developing novel therapeutic techniques, are critical targets for continued advancement in lung cancer treatment. In the present study, we aimed to find key regulatory genes in the progression of Cisplatin resistance in A-549 lung cancer cells. In this regard, microarray dataset of Cisplatin-resistant and Cisplatin-sensitive was retrieved from the Gene Expression Omnibus (GEO) with accession number of GSE108214. Then, differentially expressed genes (DEGs) between sensitive and resistant lung cancer cells were obtained by using R software v4.0.2 and related packages. We recognized CEACAM1, DGKA, ARHGEF4, and THSD4 are involved in the drug resistance. Experimentally, Cisplatin-resistant A-549 cells were developed and analyzed by MTT assay. Besides, the expression of candidate genes were analyzed in these cells compared to Cisplatin-sensitive A-549 cells by qRT-PCR. The findings presented that the expression of CEACAM1, DGKA, ARHGEF4, and THSD4 was altered following the induction of Cisplatin resistance in A549 cells.

Nicotine-induced miR-21-3p promotes chemoresistance in lung cancer by negatively regulating FOXO3a

Lung cancer is the leading cause of cancer-related mortality worldwide and cigarette smoking is reported to contribute to the lung cancer-related mortality. The present study aimed to investigate the molecular mechanism underlying nicotine-induced chemoresistance in lung cancer. The expression of microRNA (miR)-21-3p and its predicted target FOXO3a in lung cancer cells was detected via reverse transcription-quantitative PCR, in the presence or absence of nicotine. The regulatory effect of miR-21-3p and FOXO3a on lung cancer cell proliferation and apoptosis induced by docetaxel or cisplatin treatment was evaluated by performing Cell Counting Kit-8 and Annexin V/PI staining assays, respectively. The interaction between miR-21-3p and FOXO3a was analyzed by performing luciferase reporter assays and western blotting. FOXO3a overexpression rescue experiments were conducted in vitro and in vivo using a xenograft mouse model to assess the function of miR-21-3p/FOXO3a in lung cancer. Nicotine induced miR-21-3p expression in lung cancer cells in a dose-dependent manner. miR-21-3p downregulated FOXO3a expression by directly binding to the 3′-untranslated region of FOXO3a. Moreover, miR-21-3p knockdown sensitized lung cancer cells to docetaxel or cisplatin treatment. Mechanistically, FOXO3a was predicted as a direct target of miR-21-3p. FOXO3a overexpression promoted the chemosensitivity of lung cancer cells to docetaxel or cisplatin treatment. Furthermore, FOXO3a overexpression antagonized the regulatory function of miR-21-3p on docetaxel- or cisplatin-treated lung cancer cells. In the docetaxel- or cisplatin-treated lung cancer xenograft mouse model, miR-21-3p promoted chemoresistance via negatively regulating FOXO3a. Therefore, the present study demonstrated that nicotine-induced miR-21-3p promoted chemoresistance to docetaxel or cisplatin treatment via negatively regulating FOXO3a, which may serve as a novel therapeutic strategy for the treatment of patients with chemoresistant lung cancer.

Role of H2A.Z.1 in epithelial-mesenchymal transition and radiation resistance of lung adenocarcinoma in vitro

Radiation resistance reduces patient survival and is an important challenge in treating lung adenocarcinoma (LUAD). Previous studies have shown that histone H2A variants can affect the radiosensitivity of tumors; however, the main role of histone H2A variants in LUAD remains unclear. Using the TCGA database, we found that histone H2A variant H2A.Z.1 is positively associated with the progression and poor prognosis of LUAD. Colony formation, scratch wound-healing, and transwell assays as well as Western blot were performed to assess the role of H2A.Z.1 in vitro. Results suggested that H2A.Z.1 promoted cell migration and invasion, epithelial-mesenchymal transition, stemness, and radiation resistance in LUAD cells. Targeting H2A.Z.1 in combination with radiation therapy could be a potential therapeutic approach for radiation resistant LUAD.

Time Interval to Initiation of Whole-Brain Radiation Therapy in Patients With Small Cell Lung Cancer With Brain Metastasis

Purpose

Patients with small cell lung cancer (SCLC) who have brain metastases require whole-brain radiation therapy (WBRT). When there is no emergent indication for WBRT, patients may receive systemic therapy first and WBRT afterward. In scenarios when systemic therapy is initiated first, it has not been previously investigated whether delaying WBRT is harmful.

Methods and Materials

The National Cancer Database was queried (2004-2016) for patients with SCLC with brain metastases who received 30 Gy in 10 fractions of WBRT. Patients were divided into groups based on whether they received early WBRT (3-14 days after initiation of chemotherapy) or late WBRT (15-90 days after initiation of chemotherapy). Demographic and clinicopathologic categorical variables were compared between those who had early WBRT (3-14 days) and those who had late WBRT (15-90 days). Factors predictive for late WBRT were determined. Overall survival (OS), which was defined as days from diagnosis to death, was evaluated and variables prognostic for OS were determined.

Results

A total of 1082 patients met selection criteria; 587 (54%) had early WBRT and 495 (46%) received late WBRT. Groups were similarly distributed aside from days from initiating chemotherapy to initiating WBRT (P < .001). The early WBRT group had a median of 7 days (interquartile range [IQR], 5-10 days) from initiating chemotherapy to initiating WBRT and the late WBRT group had a median of 34 days (IQR, 21-57 days). On binary logistic regression analysis, a longer time interval between diagnosis and the start of systemic therapy was predictive for later WBRT. Median OS was 8.7 months for early WBRT and 7.5 months for late WBRT (hazard ratio [HR], 1.165; P = .008). Early WBRT (P = .02), female sex (P = .045), and private insurance (P = .04) were favorable prognostic factors for OS on multivariable analysis, whereas older age (P = .006) was an unfavorable prognostic factor.

Conclusions

Patients with SCLC and brain metastases who received early WBRT were found to have a modest improvement in OS compared with patients who received late WBRT. These findings suggest that early WBRT should be offered to patients who have brain metastases, even in the absence of an indication for emergent WBRT.

mRNA Network: Solution for Tracking Chemotherapy Insensitivity in Small-Cell Lung Cancer

Background

Small-cell lung cancer (SCLC) has poor prognosis and is prone to drug resistance. It is necessary to search for possible influencing factors for SCLC chemotherapy insensitivity. Therefore, we proposed an mRNA network to track the chemotherapy insensitivity in SCLC.

Methods

Six samples of patients with SCLC were recruited for RNA sequencing. TopHat2 and Cufflinks were used to make differential analysis. Functional analysis was applied as well. Finally, multidimensional validation was applied for verifying the results we obtained by experiment.

Results

This study was a trial of drug resistance in 6 SCLC patients after first-line chemotherapy. The top 10 downregulated genes differentially expressed in the chemo-insensitive group were SERPING1, DRD5, PARVG, PRAME, NKX1-1, MCTP2, PID1, PLEKHA4, SPP1, and SLN. Cell-cell signaling by Wnt (p=6.98E - 21) was the most significantly enriched GO term in biological process, while systemic lupus erythematosus (p=6.97E - 10), alcoholism (p=1.01E - 09), and transcriptional misregulation in cancer (p=0.00227988) were the top three ones of KEGG pathways. In multiple public databases, we also highlighted and verified the vital role of glycolysis/gluconeogenesis pathway and corresponding genes in chemo-insensitivity in SCLC.

Conclusion

Our study confirmed some SCLC chemotherapy insensitivity-related genes, biological processes, and pathways, thus constructing the chemotherapy-insensitive network for SCLC.

Antitumor effects of 3-bromoascochlorin on small cell lung cancer via inhibiting MAPK pathway

Small cell lung cancer (SCLC) was defined as a recalcitrant cancer, and novel therapies are urgently needed. Marine natural products (MNPs) may bring continuing hope for treatment of SCLC. In this study, 3-bromoascochlorin (BAS), an MNP isolated from the coral-derived fungus Acremonium sclerotigenum GXIMD 02501, was primarily screened out with antiproliferative activity towards SCLC cell lines. Then western blot analysis (WB) and flow cytometry were conducted, and we found BAS could induce the apoptosis of H446 and H69AR cells. Besides, BAS could suppress the invasion and migration of H446. In an SCLC xenograft mice model, BAS inhibited the growth of tumor without affecting the body weight of mice. Finally, the underlying mechanisms were preliminarily explored. According to the results of RNA-seq, reverse transcription-quantitative polymerase chain reaction, and WB, our results revealed that BAS exerted antitumor activity via inhibiting mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinases (ERK) pathway. Collectively, these results indicated that BAS can be used as a promising compound for the treatment of human SCLC.

Pseudo-ginsenoside Rh2 Induces Protective Autophagy in Hepatocellular Carcinoma HepG2 Cells

BACKGROUND

Pseudo-ginsenoside-Rh2 (pseudo-G-Rh2), a novel derivative of ginsenoside Rh2, is reported to exert a pro-apoptotic effect on various malignancies. However, whether this anti-cancer action of pseudo-G-Rh2 involves autophagy remains to be determined and explored.

OBJECTIVES

Investigation of pseudo-G-Rh2-induced apoptosis and autophagy and the underlying mechanism.

METHODS

In the present study, the MTT assay was used for evaluating cell viability and the lactate dehydrogenase (LDH) assay was performed to assess cell toxicity. Autophagy evaluation was performed using monodansylcadaverine (MDC) staining and transmission electron microscopy (TEM). The levels of autophagy-associated and apoptosis-associated proteins were determined using Western blotting. The Annexin V FITC/propidium iodide (PI) assay was used to assess apoptosis.

RESULTS

The Annexin V FITC/PI assay revealed that the percentage of apoptotic cells in HepG2 cells at concentrations 0, 20, 40, and 60 μM was 3.75%±1.37%, 5.70%±1.04%, 12.30%±2.10%, and 34.26%±4.73%, respectively. Pseudo-G-Rh2 was observed to significantly increase the expressions of BAX, cleaved-caspase-3, and cleaved-caspase-9, while it decreased the Bcl-2 expression. MDC and TEM analyses revealed that pseudo-G-Rh2 at concentrations 20, 40, and 60 μM significantly facilitated the accumulation of autophagosomes and autolysosomes within the HepG2 cells. Moreover, pseudo-G-Rh2 significantly increased the expressions of LC3 Ⅱ/LC3 Ⅰ, and Beclin-1 and decreased the expression of p62. The Annexin V FITC/PI assay also revealed that in comparison to the pseudo-G-Rh2 group, the concurrent treatment with pseudo-G-Rh2 and an autophagy inhibitor (CQ or 3-MA) significantly induced distinct apoptosis. In addition, pseudo-G-Rh2 activated AMPK and inhibited the PI3K/Akt/mTOR pathway in a concentration-dependent manner. Pseudo-G-Rh2 is similar to the current patents, which enhanced its anti-cancer activity by combining with autophagy inhibitors.

CONCLUSION

Pseudo-G-Rh2 could induce protective autophagy in HepG2 cells, at least in part, via AMPK and the PI3K/Akt/mTOR pathway.

Combination of two miRNAs has a stronger effect on stimulating apoptosis, inhibiting cell growth, and increasing erlotinib sensitivity relative to single miRNA in A549 lung cancer cells

Despite the dramatic efficacy of EGFR-TKIs, most of non-small cell lung cancer patients ultimately develop resistance to these agents. In this study, we explored the effects of miRNA-125a-5p and miRNA-145, alone or in combination, EGFR expression, cell growth and sensitivity of the NSCLC cells to erlotinib. The expression of EGFR was measured using RT-qPCR and Western blotting. The effect of miRNAs and erlotinib on cell growth and survival was assessed by trypan blue assay and MTT assay, respectively. Apoptosis was measured using ELISA cell death assay. We found that transfection of miRNA-125a-5p and miRNA-145 significantly inhibited the expression of EGFR mRNA and protein in a time-dependent manner (p < 0.05 vs. blank control or negative control miRNA). ANOVA and Bonferroni's test were used to ascertain significant differences between groups. Other experiments indicated that upregulation of each of miRNA-125a-5p or miRNA-145 inhibited cell growth, induced apoptosis, and markedly decreased the IC₅₀ value of erlotinib in A549 lung cancer cells (p < 0.05). Moreover, the combination of two miRNAs showed a stronger effect on cells survival, apoptosis, and drug sensitivity, relative to single miRNA (p < 0.05). The results of our study indicate that the therapeutic delivery of miRNA-145 and miRNA-125a-5p to lung cancer may inhibit cell proliferation, trigger apoptosis, and sensitize lung cancer cells to EGFR-TKIs.

The landscape of small cell lung cancer metastases: Organ specificity and timing

BACKGROUND

Early metastasis is a hallmark of small cell lung cancer (SCLC). However, the mechanisms and resulting patterns of SCLC dissemination are unclear. Our aim was thus to investigate the organ specificity and timing of blood-borne metastases in a comprehensive large cohort of SCLC patients.

METHODS

In this retrospective non-interventional cross-sectional study of 1009 Caucasian SCLC patients, we investigated the correlation between the distinct locations of the primary tumor and metastatic sites.

RESULTS

The onset of bone (p < 0.001), brain (p < 0.001), and pericardial (p = 0.02) metastases were late events, whereas adrenal gland (p = 0.005) and liver (p < 0.001) metastases occurred earlier. No significant difference was found in the distribution of early versus late metastases when comparing central and peripheral primary tumors. Patients with bone metastases had a higher than expected likelihood of having liver metastases, while brain metastases tended to appear together with adrenal gland metastases. Pleural and both lung and pericardial metastases also tended to co-metastasize together more frequently than expected if metastatic events occurred independently. Notably, patients with central primary tumors had decreased median overall survival (OS) compared to those with peripheral tumors, although this tendency does not appear to be significant (p = 0.072).

CONCLUSION

Our results are suggestive for particular site- and sequence-specific metastasis patterns in human SCLC. SCLC bone metastases tend to appear together with liver metastases, while brain metastases occur together with adrenal gland metastases. Better understanding of metastasis distribution patterns might help to improve the diagnosis and therapeutic decision-making in SCLC patients.

Emodin enhances cisplatin sensitivity in non-small cell lung cancer through Pgp downregulation

Cisplatin resistance is one of the main causes of chemotherapy failure and tumor progression in non-small cell lung cancer (NSCLC). Emodin has been demonstrated to induce NSCLC cell apoptosis and act as a potential cancer therapeutic agent. However, whether emodin could affect NSCLC cell sensitivity toward cisplatin remains unclear. The present study aimed to determine the effect of emodin and cisplatin combination on the chemosensitivity of NSCLC cells. A549 and H460 cells were treated with different concentrations of cisplatin and/or emodin. Cell Counting Kit-8, fluorescence microscopy, immunofluorescence assays and flow cytometry were used to determine cell proliferation, drug efflux, DNA damage level and cell apoptosis, respectively. P-glycoprotein (Pgp) and multidrug resistance-associated protein 1 (MRP1) expression was detected by western blotting. The results demonstrated that emodin and cisplatin inhibited the proliferation of A549 and H460 cells. Furthermore, emodin inhibited the drug efflux in A549 and H460 cells in a dose-dependent manner. In addition, emodin enhanced cisplatin-induced apoptosis and DNA damage in A549 and H460 cells. Emodin also decreased Pgp expression in A549 and H460 cells in a dose-dependent manner; however, it had no effect on MRP1 expression. Taken together, the results from the present study demonstrated that emodin can increase A549 and H460 cell sensitivity to cisplatin by inhibiting Pgp expression. Emodin may therefore be considered as an effective adjuvant for cisplatin treatment.

Gene Therapy with MiRNA-Mediated Targeting of Mcl-1 Promotes the Sensitivity of Non-Small Cell Lung Cancer Cells to Treatment with ABT-737

BACKGROUND

Despite the dramatic efficacy of ABT-737, a large percentage of cancer cells ultimately become resistance to this drug. Evidences show that over-expression of Mcl-1 is linked to ABT-737 resistance in NSCLC cells. The aim of this study was to investigate the effect of miRNA-101 on Mcl-1 expression and sensitivity of the A549 NSCLC cells to ABT-737.

METHODS

After miRNA-101 transfection, the Mcl-1 mRNA expression levels were quantified by RT-qPCR. Trypan blue staining was used to explore the effect of miRNA-101 on cell growth. The cytotoxic effects of miRNA-101 and ABT-737, alone and in combination, were measured using MTT assay. The effect of drugs combination was determined using the method of Chou-Talalay. Cell death was assessed using cell death detection ELISA assay kit.

RESULTS

Results showed that miRNA-101 markedly suppressed the expression of Mcl-1 mRNA in a time dependent manner, which led to A549 cell proliferation inhibition and enhancement of apoptosis (p < 0.05, relative to blank control). Pretreatment with miRNA-101 synergistically decreased the cell survival rate and lowered the IC50 value of ABT-737. Furthermore, miRNA-101 dramatically enhanced the apoptotic effect of ABT-737. Negative control miRNA had no remarkable effect on cellular parameters.

CONCLUSIONS

Our findings propose that suppression of Mcl-1 by miRNA-101 can effectively inhibit the cell growth and sensitize A549 cells to ABT-737. Therefore, miRNA-101 can be considered as a potential therapeutic target in patients with non-small cell lung cancer.
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