Overcoming chemotherapy resistance via simultaneous drug-efflux circumvention and mitochondrial targeting

Multidrug resistance(MDR) has been considered as a huge challenge to the effective chemotherapy. Therefore, it is necessary to develop new strategies to effectively overcome MDR. Here,based on the previous research of N-(2-hydroxypropyl)methacrylamide(HPMA) polymer–drug conjugates, we designed an effective system that combined drug-efflux circumvention and mitochondria targeting of anticancer drug doxorubicin(Dox). Briefly, Dox was modified with mitochondrial membrane penetrating peptide(MPP) and then attached to(HPMA) copolymers(P-M-Dox). Our study showed that macromolecular HPMA copolymers successfully bypassed drug efflux pumps and escorted Dox into resistant MCF-7/ADR cells via endocytic pathway. Subsequently, the mitochondria accumulation of drugs was significantly enhanced with 11.6-fold increase by MPP modification. The excellent mitochondria targeting then resulted in significant enhancement of reactive oxygen species(ROS) as well as reduction of adenosine triphosphate(ATP)production, which could further inhibit drug efflux and resistant cancer cell growth. By reversing Dox resistance, P-M-Dox achieved much better suppression in the growth of 3D MCF-7/ADR tumor spheroids compared with free Dox. Hence, our study provides a promising approach to treat drug-resistant cancer through simultaneous drug efflux circumvention and direct mitochondria delivery.

Immunogenic hydrogel toolkit disturbing residual tumor “seeds” and pre-metastatic “soil” for inhibition of postoperative tumor recurrence and metastasis

Tumor recurrence and metastasis is the leading cause of mortality for postoperative breast cancer patients. However, chemotherapy intervention after surgery is often unsatisfactory, because residual microtumors are difficult to target and require frequent administration. Here, an all-in-one and oncefor-all drug depot based on in situ-formed hydrogel was applied to fit the irregular surgical trauma, and enable direct contact with residual tumors and sustained drug release. Our immunological analysis after resection of orthotopic breast tumor revealed that postsurgical activation of CXCR4-CXCL12 signal exacerbated the immunosuppression and correlated with adaptive upregulation of PD-L1 in recurrent tumors. Thus, a multifunctional hydrogel toolkit was developed integrating strategies of CXCR4 inhibition,immunogenicity activation and PD-L1 blockade. Our results showed that the hydrogel toolkit not only exerted local effect on inhibiting residual tumor cell “seeds” but also resulted in abscopal effect on disturbing pre-metastatic “soil”. Furthermore, vaccine-like effect and durable antitumor memory were generated, which resisted a secondary tumor rechallenge in 100% cured mice. Strikingly, one single dose of such modality was able to eradicate recurrent tumors, completely prevent pulmonary metastasis and minimize off-target toxicity, thus providing an effective option for postoperative intervention.

Co-delivery of mitochondrial targeted lonidamine and PIN1 inhibitor ATRA by nanoparticulate systems for synergistic metastasis suppression

Mitochondria are highly involved in the metastasis of cancer cells.However,tumor cells impede the efficiency of mitochondrial targeted drugs by protecting mitochondria through an intrinsic and adaptive antioxidant mechanism.We aim to disturb the redox homeostasis by prolyl-isomerase PIN1 inhibitor all-trans retinoic acid(ATRA)to improve the therapeutic efficacy of mitochondrial targeted lonidamine(TL).The combination of ATRA and TL with a ratio of 2:1 was found to have the best synergistic effect in inhibiting the proliferation and metastasis of metastatic 4T1 breast cancer cells.Dual-drug loaded nanoparticles(TL-ATRA NPs)were further developed by self-assembly and were observed to disturb the redox homeostasis drastically and triggered a robust mitochondrial disruption on metastatic 4T1 breast cancer cells.The molecular mechanism was related to the downregulation of nuclear factor E2-related factor 2(NRF2),a critical transcription factor that regulated antioxidant responses,and its downstream molecules.As a result,TL-ATRA NPs significantly suppressed the growth of primary tumors and the formation of lung metastasis nodes.Collectively,our findings showed that sensitizing mitochondria to anti-cancer drugs by disturbing redox homeostasis achieved a satisfactory therapeutic effect to inhibit tumor growth and metastasis.

Spatially targeting of tumor-associated macrophages and cancer cells for suppression of spontaneously metastatic tumor

The interaction between cancer cells and M2 tumor-associated macrophages(M2-TAMs)facilitates tumor growth and metastasis.However,cancer cells and M2-TAMs have different spatial distribution patterns,which requires distinct drug delivery strategies.Herein,based on different tumor-penetrating ability of nanocarriers,we developed a combinatory strategy that consists of a TAMs-targeting liposome(alanine-alanine-asparagine(AAN)-Lip-regorafenib(Rego))and a cancer cells-targeting copolymer(internalizing RGD modified with N-(2-hydroxypropyl)methacrylamide-doxorubicin(iRGD-HD)).Our study confirmed AAN-Lip-Rego accumulated at perivascular sites where M2-TAM is located,while iRGD-HD penetrated into deep site of tumor to enter cancer cells.Thereafter,we found iRGD-HD induced cancer cells undergoing immunogenic cell death to enhance tumor infiltration of CD8^(+)T cells.Meanwhile,AAN-Lip-Rego efficiently repolarized TAMs from M2 into M1 to alleviate tumor immunosuppression,thus reviving CD8^(+)T cells.Moreover,the repolarization of TAMs led to dramatic downregulation of prometastatic factors expressed on cancer cells.As a result,such combinatory approach elicited robust antitumor immune responses and generated considerable anti-tumor and anti-metastasis efficacy to markedly inhibit primary tumor and spontaneous lung metastasis.