Lam Kuen Kuen, Low Yee Syuen, Lo Michelle, Wong Michelle, Leong Tang Choong, Tan Emile, Chok Aik Yong, Seow-En Isaac, Wong Siew Heng, Cheah Peh Yean
Department of Colorectal Surgery, Singapore General Hospital, Singapore, Singapore.
JW Bioscience Pte. Ltd., Singapore, Singapore.
Front Oncol. 2023 Mar 27;13:1036871. doi: 10.3389/fonc.2023.1036871. eCollection 2023.
Colorectal cancer (CRC) is the third highest incidence cancer and a leading cause of cancer mortality worldwide. To date, chemotherapeutic treatment of advanced CRC that has metastasized has a dismayed success rate of less than 30%. Further, most (80%) sporadic CRCs are microsatellite-stable and are refractory to immune checkpoint blockade therapy. KRAS is a gatekeeper gene in colorectal tumorigenesis. Nevertheless, KRAS is 'undruggable' due to its structure. Thus, focus has been diverted to develop small molecule inhibitors for its downstream effector such as ERK/MAPK. Despite intense research efforts for the past few decades, no small molecule inhibitor has been in clinical use for CRC. Antibody targeting KRAS itself is an attractive alternative. We developed a transient patient-derived matched mucosa-tumor primary culture to assess whether anti-KRAS antibody can be internalized to bind and inactivate KRAS. We showed that anti-KRAS antibody can enter live mucosa-tumor cells and specifically aggregate KRAS in the cytoplasm, thus hindering its translocation to the inner plasma membrane. The mis-localization of KRAS reduces KRAS dwelling time at the site where it tethers to activate downstream effectors. We previously showed that expression of SOX9 was KRAS-mutation-dependent and possibly a better effector than ERK in CRC. Herein, we showed that anti-KRAS antibody treated tumor cells have less intense SOX9 cytoplasmic and nuclear staining compared to untreated cells. Our results demonstrated that internalized anti-KRAS antibody inhibits KRAS function in tumor. With an efficient intracellular antibody delivery system, this can be further developed as combinatorial therapeutics for CRC and other KRAS-driven cancers.
结直肠癌（CRC）是全球发病率第三高的癌症，也是癌症死亡的主要原因。迄今为止，对已发生转移的晚期CRC进行化疗的成功率令人沮丧，低于30%。此外，大多数（80%）散发性CRC是微卫星稳定的，对免疫检查点阻断疗法难治。KRAS是结直肠癌发生中的一个守门基因。然而，由于其结构，KRAS是“不可成药的”。因此，研究重点已转向开发针对其下游效应器如ERK/MAPK的小分子抑制剂。尽管在过去几十年中进行了大量研究，但尚无小分子抑制剂用于CRC的临床治疗。靶向KRAS本身的抗体是一种有吸引力的替代方案。我们开发了一种短暂的患者来源的匹配黏膜-肿瘤原代培养物，以评估抗KRAS抗体是否可以内化以结合并使KRAS失活。我们表明，抗KRAS抗体可以进入活的黏膜-肿瘤细胞，并在细胞质中特异性聚集KRAS，从而阻碍其向内质膜的转运。KRAS的错误定位减少了KRAS在其结合以激活下游效应器的位点的停留时间。我们之前表明，SOX9的表达依赖于KRAS突变，并且在CRC中可能是比ERK更好的效应器。在此，我们表明，与未处理的细胞相比，抗KRAS抗体处理的肿瘤细胞中SOX9的细胞质和细胞核染色强度较低。我们的结果表明，内化的抗KRAS抗体在肿瘤中抑制KRAS功能。通过高效的细胞内抗体递送系统，这可以进一步开发为CRC和其他KRAS驱动癌症的联合治疗方法。
