Proteasome inhibitor bortezomib enhances the effect of standard chemotherapy in small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive cancer showing a very poor prognosis because of metastasis formation at an early stage and acquisition of chemoresistance. One key driver of chemoresistance is the transcription factor Forkhead box protein M1 (FOXM1) that regulates cell cycle proliferation, maintenance of genomic stability, DNA damage response, and cell differentiation in numerous tumor entities. In this study we investigated the role of FOXM1 in SCLC progression and analyzed the effect of FOXM1 inhibition using two proteasome inhibitors, bortezomib and siomycin A. FOXM1 was strongly expressed in patient-derived SCLC samples (n=123) and its nuclear localization was associated with the proliferation marker Ki-67. Both proteasome inhibitors successfully inhibited FOXM1 expression leading to a significantly reduced proliferation and a decreased mitotic rate along with cell cycle arrest and apoptosis induction. These effects were further enhanced by addition of bortezomib to standard chemotherapy. Treatment of mice bearing chemoresistant SCLC xenografts with bortezomib reduced the mean bioluminescence signal of tumors by 54%. Similarly, treatment with cisplatin as a standard chemotherapy reduced the mean bioluminescence signal of tumors by 58%. However, in combination with standard chemotherapy bortezomib further reduced the mean bioluminescence signal by 93% (p=0.0258). In conclusion, we demonstrate the effect of bortezomib in inhibiting FOXM1 expression and thus in sensitizing resistant SCLC cells to standard chemotherapy. Thus, addition of bortezomib to standard chemotherapy might potently improve SCLC therapy, particularly in an extensive cancer stage.

Mechanisms of Targeting the MDM2-p53-FOXM1 Axis in Well-Differentiated Intestinal Neuroendocrine Tumors

BACKGROUND/AIMS

The tumor suppressor p53 is rarely mutated in gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN) but they frequently show a strong expression of negative regulators of p53, rendering these tumors excellent targets for a p53 recovery therapy. Therefore, we analyzed the mechanisms of a p53 recovery therapy on intestinal neuroendocrine tumors in vitro and in vivo.

METHODS

By Western blot and immunohistochemistry, we found that in GEP-NEN biopsy material overexpression of MDM2 was present in intestinal NEN. Therefore, we analyzed the effect of a small-molecule inhibitor, nutlin-3a, in p53 wild-type and mutant GEP-NEN cell lines by proliferation assay, flow cytometry, immunofluorescence, Western blot, and by multiplex gene expression analysis. Finally, we analyzed the antitumor effect of nutlin-3a in a xenograft mouse model in vivo. During the study, the tumor volume was determined.

RESULTS

The midgut wild-type cell line KRJ-I responded to the treatment with cell cycle arrest and apoptosis. By gene expression analysis, we could demonstrate that nutlins reactivated an antiproliferative p53 response. KRJ-I-derived xenograft tumors showed a significantly decreased tumor growth upon treatment with nutlin-3a in vivo. Furthermore, our data suggest that MDM2 also influences the expression of the oncogene FOXM1 in a p53-independent manner. Subsequently, a combined treatment of nutlin-3a and cisplatin (as chemoresistance model) resulted in synergistically enhanced antiproliferative effects.

CONCLUSION

In summary, MDM2 overexpression is a frequent event in p53 wild-type intestinal neuroendocrine neoplasms and therefore recovery of a p53 response might be a novel personalized treatment approach in these tumors.

Does the proteasome inhibitor bortezomib sensitize to DNA-damaging therapy in gastroenteropancreatic neuroendocrine neoplasms? - A preclinical assessment in vitro and in vivo

BACKGROUND

Well-differentiated gastroenteropancreatic neuroendocrine neoplasms are rare tumors with a slow proliferation. They are virtually resistant to many DNA-damaging therapeutic approaches, such as chemo- and external beam therapy, which might be overcome by DNA damage inhibition induced by proteasome inhibitors such as bortezomib.

METHODS AND RESULTS

In this study, we assessed several combined treatment modalities in vitro and in vivo. By cell-based functional analyses, in a 3D in ovo and an orthotopic mouse model, we demonstrated sensitizing effects of bortezomib combined with cisplatin, radiation and peptide receptor radionuclide therapy (PRRT). By gene expression profiling and western blot, we explored the underlying mechanisms, which resulted in an impaired DNA damage repair. Therapy-induced DNA damage triggered extrinsic proapoptotic signaling as well as the induction of cell cycle arrest, leading to a decreased vital tumor volume and altered tissue composition shown by magnetic resonance imaging and F-18-FDG-PET in vivo, however with no significant additional benefit related to PRRT alone.

CONCLUSIONS

We demonstrated that bortezomib has short-term sensitizing effects when combined with DNA damaging therapy by interfering with DNA repair in vitro and in ovo. Nevertheless, due to high tumor heterogeneity after PRRT in long-term observations, we were not able to prove a therapeutic advantage of bortezomib-combined PRRT in an in vivo mouse model.

[Core curriculum Medical intensive care medicine of the German Society of Medical Intensive Care and Emergency Medicine (DGIIN)]

Medical intensive care medicine treats patients with severe, potentially life-threatening diseases covering the complete spectrum of internal medicine. The qualification in medical intensive care medicine requires a broad spectrum of knowledge and skills in medical intensive care medicine, but also in the general field of internal medicine. Both sides of the coin must be taken into account, the treatment with life-sustaining strategies of the acute illness of the patient and also the treatment of patient's underlying chronic diseases. The indispensable foundation of medical intensive care medicine as described in this curriculum includes basic knowledge and skills (level of competence I-III) as well as of behavior and attitudes. This curriculum is primarily dedicated to the internist in advanced training in medical intensive care medicine. However, this curriculum also intends to reach trainers in intensive care medicine and also the German physician chambers with their examiners, showing them which knowledge, skills as well as behavior and attitudes should be taught to trainees according to the education criteria of the German Society of Medical Intensive Care and Emergency Medicine (DGIIN).

Meta-analysis confirms improvement of hospitalizations and all-cause mortality of transcatheter mitral valve repair in functional mitral regurgitation

Background

Moderate-to-severe or severe functional mitral regurgitation (FMR) is associated with higher rates of hospitalizations and with increased mortality in heart failure (HF). Transcatheter mitral valve repair by MitraClip® implantation (TMVrMC) may effectively reduce severe MR, and is associated with symptomatic improvement. However, the long-term clinical effects of this procedure are not well defined.

Aims

We analyzed outcomes for rehospitalization and survival in HF patients with moderate-to-severe or severe FMR treated by either medical treatment (MT) only versus TMVrMC+MT by meta-analysis.

Methods and results

By systematic search of bibliographic databases, we evaluated publications comparing HF patients with FMR treated by MT only versus treatment by MT combined with TMVrMC. Studies with a minimum of 25 enrolled patients and a follow/up period of at least 12 months were deemed eligible for this meta-analysis. We identified n=7 studies enrolling 2,884 HFrEF patients, divided into two study arms: TMVrMC+MT (n=1,618), versus FMR patients receiving MT only (n=1,266). At 12 months, there was a significant reduction in all-cause mortality favoring TMVrMC+MT (OR: 0.65; CI 95% 0.53–0.79), compared with the MT only patients. At 24 months, a significant reduction of all-cause mortality in the TMVrMC+MT patient group (OR: 0.54; CI: 95%: 0.43–0.67; p<0.001) was calculated. TMVrMC+MT was associated with significantly lower rates of unplanned re-admissions for heart failure compared with MT only at 12 months (OR: 0.69; 95%; CI 0.53–0.89; p<0.001) and at 24 months (OR: 0.53; 95% CI: 0.39–0.71; p<0.001). In one publication, a survival benefit of TMVrMC+MT over MT alone was shown at 5 years post intervention (HR: 0.75; 95% CI: 0.69–0.94; p=0.012) after weighting for propensity score and controlling for age.

Conclusions

This meta-analysis on n=2,884 patients with moderate-to-severe or severe FMR reveals that TMVrMC+MT, as compared with MT alone, is associated with a significant reduction of rehospitalizations and improvement of survival up to 24 months after MitraClip implantation. However, the discordant results of 2 randomized controlled trials (MITRA-FR and COAPT) warrant further clarification, i.e. of the eligible FMR patient profiles who might benefit from TMVrMC+MT in terms of improvement of prognosis. These data imply additional evidence for TMVrMC in eligible HF patients with relevant FMR, which might be important for an update of the corresponding guidelines.

Funding Acknowledgement

Type of funding source: None