Sunitinib mesylate inhibits proliferation of human colonic stromal fibroblasts in vitro and in vivo

Role of cancer-associated fibroblasts in colorectal cancer and their potential as therapeutic targets

Cancer-associated fibroblasts (CAFs) are mesenchymal cells in the tumor microenvironment (TME). CAFs are the most abundant cellular components in the TME of solid tumors. They affect the progression and course of chemotherapy and radiotherapy in various types of tumors including colorectal cancer (CRC). CAFs can promote tumor proliferation, invasion, and metastasis; protect tumor cells from immune surveillance; and resist tumor cell apoptosis caused by chemotherapy, resulting in drug resistance to chemotherapy. In recent years, researchers have become increasingly interested CAF functions and have conducted extensive research. However, compared to other types of malignancies, our understanding of the interaction between CRC cells and CAFs remains limited. Therefore, we searched the relevant literature published in the past 10 years, and reviewed the origin, biological characteristics, heterogeneity, role in the TME, and potential therapeutic targets of CAFs, to aid future research on CAFs and tumors.

CAP1 (cyclase-associated protein 1) mediates the cyclic AMP signals that activate Rap1 in stimulating matrix adhesion of colon cancer cells

We previously reported that CAP1 (Cyclase-Associated Protein 1) regulates matrix adhesion in mammalian cells through FAK (Focal Adhesion Kinase). More recently, we discovered a phosphor-regulation mechanism for CAP1 through the Ser307/Ser309 tandem site that is of critical importance for all CAP1 functions. However, molecular mechanisms underlying the CAP1 function in adhesion and its regulation remain largely unknown. Here we report that Rap1 also facilitates the CAP1 function in adhesion, and more importantly, we identify a novel signaling pathway where CAP1 mediates the cAMP signals, through the cAMP effectors Epac (Exchange proteins directly activated by cAMP) and PKA (Protein Kinase A), to activate Rap1 in stimulating matrix adhesion in colon cancer cells. Knockdown of CAP1 led to opposite adhesion phenotypes in SW480 and HCT116 colon cancer cells, with reduced matrix adhesion and reduced FAK and Rap1 activities in SW480 cells while it stimulated matrix adhesion as well as FAK and Rap1 activities in HCT116 cells. Importantly, depletion of CAP1 abolished the stimulatory effects of the cAMP activators forskolin and isoproterenol, as well as that of Epac and PKA, on matrix adhesion in both cell types. Our results consistently support a required role for CAP1 in the cAMP activation of Rap1. Identification of the key role for CAP1 in linking the major second messenger cAMP to activation of Rap1 in stimulating adhesion, which may potentially also regulate proliferation in other cell types, not only vertically extends our knowledge on CAP biology, but also carries important translational potential for targeting CAP1 in cancer therapeutics.

Chemotherapeutic and antiangiogenic drugs beyond tumor progression in colon cancer: Evaluation of the effects of switched schedules and related pharmacodynamics

The aim of the study was to evaluate the effects and the related pharmacological mechanisms of switched schedules of antiangiogenic and chemotherapeutic drugs beyond progression after a first-line treatment in a colorectal cancer preclinical model. In vivo studies were performed in nude mice subcutaneously transplanted with colon cancer cells. The treatments included drug combinations with a switch between chemotherapeutic (i.e., irinotecan and 5-fluorouracil) and/or antiangiogenic drugs (i.e., anti-VEGF antibodies and sunitinib) at the time of tumor progression. Proliferation assays were also achieved in vitro on different colon cancer cell lines exposed to SN-38 and sunitinib alone or in combination. ABCG2 gene expression was performed with real-time PCR and SN-38 intracellular concentrations were measured. The switch in the combined treatments, at the time of tumor progression, of the chemotherapeutic (from irinotecan to 5-fluoruracil), or the antiangiogenic drug (from anti-VEGF antibodies to sunitinib) or of both drugs induced a new response. Immunohistochemistry of stromal PDGF-C, PlGF, SD1-α, Tie-2, and VEGFR-2 showed statistical differences between tumors at the time of relapse and after the switched therapy. Moreover, the combination of SN-38 and sunitinib caused synergism on colon cancer cells, with significant inhibition of the ABCG2 gene expression and an increase of SN-38 intracellular concentrations. Our observations may be of clinical relevance, suggesting the switch of single chemotherapeutic or antiangiogenic drugs beyond progression of the disease to obtain a new tumor response due to a modulation of angiogenic factors and a direct effect on tumor cells with a possible variation of intracellular drug concentrations.

Targeting tumour microenvironment by tyrosine kinase inhibitor

Tumour microenvironment (TME) is a key determinant of tumour growth and metastasis. TME could be very different for each type and location of tumour and TME may change constantly during tumour growth. Multiple counterparts in surrounding microenvironment including mesenchymal-, hematopoietic-originated cells as well as non-cellular components affect TME. Thus, therapeutics that can disrupt the tumour-favouring microenvironment should be further explored for cancer therapy. Previous efforts in unravelling the dysregulated mechanisms of TME components has identified numerous protein tyrosine kinases, while its corresponding inhibitors have demonstrated potent modulatory effect on TME. Recent works have demonstrated that beyond the direct action on cancer cells, tyrosine kinase inhibitors (TKIs) have been implicated in inactivation or normalization of dysregulated TME components leading to cancer regression. Either through re-sensitizing the tumour cells or reversing the immunological tolerance microenvironment, the emergence of these TME modulatory mechanism of TKIs supports the combinatory use of TKIs with current chemotherapy or immunotherapy for cancer therapy. Therefore, an appropriate understanding on TME modulation by TKIs may offer another mode of action of TKIs for cancer treatment. This review highlights mode of kinase activation or paracrine ligand production from TME components and summarises the findings on the potential use of various TKIs on regulating TME components. At last, the combination use of current TKIs with immunotherapy in the perspectives of efficacy and safety are discussed.

Famitinib versus placebo in the treatment of refractory metastatic colorectal cancer: a multicenter, randomized, double-blinded, placebo-controlled, phase II clinical trial

Background

Metastatic colorectal cancer (mCRC) patients with progressive disease after all available standard therapies need new medication for further treatment. Famitinib is a small-molecule multikinase inhibitor, with promising anticancer activities. This multicenter, randomized, double-blinded, placebo-controlled, phase II clinical trial was designed to evaluate the safety and efficacy of famitinib in mCRC.

Methods

Famitinib or placebo was administered orally once daily. The primary endpoint was progression-free survival (PFS). Secondary endpoints included objective response rate (ORR), disease control rate (DCR), overall survival (OS), quality-of-life (QoL), and safety.

Results

Between July 18, 2012 and Jan 22, 2014, a total of 167 patients were screened, and 154 patients were randomized in a 2:1 ratio to receive either famitinib (n = 99) or placebo (n = 55). The median PFS was 2.8 and 1.5 months in the famitinib and placebo groups (hazard ratio = 0.60, 95% confidence interval = 0.41–0.86, P = 0.004). The DCR was 59.8% and 31.4% (P = 0.002) and the ORR was 2.2% and 0.0% (P = 0.540) in the famitinib and placebo groups, respectively. The most frequent grade 3–4 adverse events were hypertension (11.1%), hand-foot syndrome (10.1%), thrombocytopenia (10.1%), and neutropenia (9.1%). Serious adverse events occurred in 11 (11.1%) patients in the famitinib group and 5 (9.1%) in the placebo group (P = 0.788). The median OS of the famitinib and placebo groups was 7.4 and 7.2 months (P = 0.657).

Conclusion

Famitinib prolonged PFS in refractory mCRC patients with acceptable tolerability.

Trial registration This study was registered on ClinicalTrials.gov (NCT01762293) and was orally presented in the 2015 ASCO-Gastrointestinal Symposium

Antitumor effect of sunitinib in human prostate cancer cells functions via autophagy

The aim of the present study was to explore sunitinib-induced autophagic effects and the specific molecular mechanisms involved, in vitro, using PC-3 and LNCaP human prostate cancer cell lines. Cells were exposed to escalating doses of sunitinib treatment and subsequent cell viability and cell cycle analyses were performed to evaluate the inhibitory effect of sunitinib in vitro. Immunofluorescence staining of microtubule associated protein 1A/1B-light chain 3 (LC3) puncta was employed to assess autophagy levels after sunitinib treatment. Western blot analysis was performed to evaluate variations in the levels of LC3, sequestosome-1, extracellular signal regulated kinase 1/2 (ERK1/2), mammalian target of rapamycin (mTOR), p70 ribosomal protein S6 kinase (p70S6K) and cleaved caspase-3 proteins. The present study revealed that sunitinib treatment inhibited cell growth and triggered autophagy in a dose-dependent manner in both cell lines. In addition, sunitinib activated ERK1/2 and inhibited mTOR/p70S6K signaling. Sunitinib-induced autophagy was notably reversed by ERK1/2 kinase inhibitor, U0126. Furthermore, inhibition of sunitinib-induced autophagy by 3-methyladenine enhanced apoptosis and exhibited improved cell viability, which indicated that sunitinib induces not only apoptosis but also autophagic cell death in prostate cancer cell lines. These results may lead to an improved understanding of the mechanism of sunitinib's cytotoxic action and may provide evidence that combined sunitinib autophagy-regulating treatment may be of benefit to anti-prostate cancer therapy.

Platelet-derived growth factor (PDGF) signalling in cancer: rapidly emerging signalling landscape

Platelet-derived growth factor (PDGF)-mediated signalling has emerged as one of the most extensively and deeply studied biological mechanism reported to be involved in regulation of growth and survival of different cell types. However, overwhelmingly increasing scientific evidence is also emphasizing on dysregulation of spatio-temporally controlled PDGF-induced signalling as a basis for cancer development. We partition this multi-component review into recently developing understanding of dysregulation PDGF signalling in different cancers, how PDGF receptors are quantitatively controlled by microRNAs. Moreover, we also summarize most recent advancements in therapeutic targeting of PDGFR as evidenced by preclinical studies. Better understanding of the PDGF-induced intracellular signalling in different cancers will be helpful in catalysing the transition from a segmented view of cancer biology to a conceptual continuum.