PD-1 and PD-L1 inhibitors in cold colorectal cancer: challenges and strategies

Colorectal cancer (CRC) is the second most common cause of cancer mortality, with mismatch repair proficient (pMMR) and/or microsatellite stable (MSS) CRC making up more than 80% of metastatic CRC. Programmed death-ligand 1 (PD-L1) and programmed death 1 (PD-1) immune checkpoint inhibitors (ICIs) are approved as monotherapy in many cancers including a subset of advanced or metastatic colorectal cancer (CRC) with deficiency in mismatch repair (dMMR) and/or high microsatellite instability (MSI-H). However, proficient mismatch repair and microsatellite stable (pMMR/MSS) cold CRCs have not shown clinical response to ICIs alone. To potentiate the anti-tumor response of PD-L1/PD-1 inhibitors in patients with MSS cold cancer, combination strategies currently being investigated include dual ICI, and PD-L1/PD-1 inhibitors in combination with chemotherapy, radiotherapy, vascular endothelial growth factor (VEGF) /VEGF receptor (VEGFR) inhibitors, mitogen-activated protein kinase (MEK) inhibitors, and signal transducer and activation of transcription 3 (STAT3) inhibitors. This paper will review the mechanisms of PD-1/PD-L1 ICI resistance in pMMR/MSS CRC and potential combination strategies to overcome this resistance, summarize the published clinical experience with different combination therapies, and make recommendations for future avenues of research.

[Effect of Tripterygium wilfordii on Th1, Th2 cytokines production in asthma patients]

OBJECTIVE

To observe the effect of Tripterygium wilfordii on Th1, Th2 cytokines in asthma patients for further study on the therapeutic mechanism.

METHODS

Twelve patients of middle or severe asthma were treated by Tripterygium polyglucoside 40 mg or 60 mg daily for 4 weeks. Blood of patients was colleted before and after treatment for serum and peripherol blood mononuclear cells (PBMC) preparation. The prepared PBMCs were stimulted in vitro with Concanavalin A (ConA) for 6 hrs and followed by culturing with Triptolide for 24 hrs and then the supernatant was collected. The concentration of interleukin-2(IL-2), -4(IL-4), -5(IL-5) and interferon-gamma(IFN-gamma) in serum and in the supernatant were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum levels of IL-2, IL-4 and IL-5 of patients decreased significantly after treatment of Tripterygium polyglucoside (P < 0.01), but IFN-gamma level was under the detection sensitivity both before and after treatment. Triptolide could inhibit PBMC to secrete IL-2, IL-4 and IL-5 in vitro (P < 0.01), but IFN-gamma was also under the detection sensitivity.

CONCLUSION

The marked inhibition of Th2 cytokine expression by Tripterygium was the important mechanism of it in treating asthma. But the fact that Tripterygium also showed inhibition on Th1 cytokine indicated that the inhibition of Tripterygium on Th2 and Th1 cytokines was non-specific.